Mutations in LMNA cause a variety of diseases affecting striated muscle including autosomal Emery-Dreifuss muscular dystrophy (EDMD), LMNA-associated congenital muscular dystrophy (L-CMD), and limb-girdle muscular dystrophy
type 1B (LGMD1B). Here, we describe novel and recurrent LMNA mutations identified in 50 patients from the United States and Canada, which is the first report of the distribution of LMNA mutations from a large cohort outside Europe. This augments the number of LMNA mutations known to cause EDMD by 16.5%, equating to an increase of 5.9% in the total known LMNA mutations. Eight patients presented with either p.R249W/Q or p.E358K mutations and an early onset EDMD phenotype: two mutations recently associated with L-CMD. Importantly, 15 mutations are novel and include eight missense mutations (p.R189P, p.F206L, p.S268P, p.S295P, p.E361K, p.G449D, p.L454P, and p.W467R), three splice site mutations (c.IVS4 + 1G>A, c.IVS6 - 2A>G, and c.IVS8 + 1G>A), one duplication/in frame insertion (p.R190dup), one deletion (p.Q355del), and two silent mutations (p.R119R and p.K270K). Analysis of 4 of our lamin A mutations showed that some caused nuclear deformations and lamin B redistribution in a mutation specific manner. Together, this study significantly augments the number of EDMD patients on the database and describes 15 novel mutations that underlie EDMD, which will contribute to establishing genotype-phenotype correlations.
Chen L, etal., Lancet. 2003 Aug 9;362(9382):440-5.
BACKGROUND: Werner's syndrome is a progeroid syndrome caused by mutations at the WRN helicase locus. Some features of this disorder are also present in laminopathies caused by mutant LMNA encoding nuclear lamin A/C. Because of this similarity, we sequ
enced LMNA in individuals with atypical Werner's syndrome (wild-type WRN). METHODS: Of 129 index patients referred to our international registry for molecular diagnosis of Werner's syndrome, 26 (20%) had wildtype WRN coding regions and were categorised as having atypical Werner's syndrome on the basis of molecular criteria. We sequenced all exons of LMNA in these individuals. Mutations were confirmed at the mRNA level by RT-PCR sequencing. In one patient in whom an LMNA mutation was detected and fibroblasts were available, we established nuclear morphology and subnuclear localisation. FINDINGS: In four (15%) of 26 patients with atypical Werner's syndrome, we noted heterozygosity for novel missense mutations in LMNA, specifically A57P, R133L (in two people), and L140R. The mutations altered relatively conserved residues within lamin A/C. Fibroblasts from the patient with the L140R mutation had a substantially enhanced proportion of nuclei with altered morphology and mislocalised lamins. Individuals with atypical Werner's syndrome with mutations in LMNA had a more severe phenotype than did those with the disorder due to mutant WRN. INTERPRETATION: Our findings indicate that Werner's syndrome is molecularly heterogeneous, and a subset of the disorder can be judged a laminopathy.
Scleroderma is a rare multisystemic disease of unknown etiology presumed to develop in genetically predisposed patients. Since patients affected with scleroderma develop clinical features similar to those observed in some laminopathies, we decided to screen at the genomic level a cohort of 27 patien
ts affected with either localized or systemic scleroderma for mutations in three lamin-related genes: LMNA, encoding A-type lamins; ZMPSTE24, encoding a protease involved in lamin A processing; and LBR, encoding the lamin B receptor. No mutation was retrieved, whereas 25 polymorphic sequence variations were identified, 7 of which were unreported. Functional analyses performed for three of these allowed exclusion of an impact on splicing. Multiplex ligation-dependent probe amplification analysis showed no LMNA deletion or duplication. Altogether our results suggest that LMNA, ZMPSTE24, and LBR sequence variations are not major genetic determinants involved in scleroderma pathogenesis.
Nguyen D, etal., Biochem Biophys Res Commun. 2007 Jan 19;352(3):603-8. doi: 10.1016/j.bbrc.2006.11.070. Epub 2006 Nov 27.
Laminopathies are a group of genetic disorders caused by LMNA mutations; they include muscular dystrophies, lipodystrophies, and progeroid syndromes. We identified a novel heterozygous LMNA mutation, L59R, in a patient with
the general appearance of mandibuloacral dysplasia and progeroid features. Examination of the nuclei of dermal fibroblasts revealed the irregular morphology characteristic of LMNA mutant cells. The nuclear morphological abnormalities of LMNA mutant lymphoblastoid cell lines were less prominent compared to those of primary fibroblasts. Since it has been reported that progeroid features are associated with increased extracellular matrix in dermal tissues, we compared a subset of these components in fibroblast cultures from LMNA mutants with those of control fibroblasts. There was no evidence of intracellular accumulation or altered mobility of collagen chains, or altered conversion of procollagen to collagen, suggesting that skin fibroblast-mediated matrix production may not play a significant role in the pathogenesis of this particular laminopathy.
The lipodystrophies are a group of disorders characterized by the absence or reduction of subcutaneous adipose tissue. Partial lipodystrophy (PLD; MIM 151660) is an inherited condition in which a regional (trunk and limbs) loss of fat occurs during the peri-pubertal phase. Additionally, variable deg
rees of resistance to insulin action, together with a hyperlipidaemic state, may occur and simulate the metabolic features commonly associated with predisposition to atherosclerotic disease. The PLD locus has been mapped to chromosome 1q with no evidence of genetic heterogeneity. We, and others, have refined the location to a 5.3-cM interval between markers D1S305 and D1S1600 (refs 5, 6). Through a positional cloning approach we have identified five different missense mutations in LMNA among ten kindreds and three individuals with PLD. The protein product of LMNA is lamin A/C, which is a component of the nuclear envelope. Heterozygous mutations in LMNA have recently been identified in kindreds with the variant form of muscular dystrophy (MD) known as autosomal dominant Emery-Dreifuss MD (EDMD-AD; ref. 7) and dilated cardiomyopathy and conduction-system disease (CMD1A). As LMNA is ubiquitously expressed, the finding of site-specific amino acid substitutions in PLD, EDMD-AD and CMD1A reveals distinct functional domains of the lamin A/C protein required for the maintenance and integrity of different cell types.
Mutations in LMNA cause wide variety of disorders including Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy, and congenital muscular dystrophy. We recently found a LMNA mutation in a patient who was previou
sly diagnosed as infantile onset inflammatory myopathy. In this study, we screened for LMNA mutations in 20 patients suspected to have inflammatory myopathy with onset at 2years or younger. The diagnosis of inflammatory myopathy was based on muscle pathology with presence of perivascular cuffing and/or endomysial/perimysial lymphocyte infiltration. We identified heterozygous LMNA mutations in 11 patients (55%), who eventually developed joint contractures and/or cardiac involvement after the infantile period. Our findings suggest that LMNA mutation should be considered in myopathy patients with inflammatory changes during infancy, and that this may help avoid life-threatening events associated with laminopathy.
Werner syndrome (WS) is a pleiotropic disease of premature aging involving short stature, tight, atrophied, and/or ulcerated skin; a characteristic 'birdlike' facies and high, squeaky or hoarse voice; premature greying and thinning of the hair; and early onset cataracts. Additional common symptoms
include diabetes mellitus, hypogonadism, osteoporosis, osteosclerosis of the digits, soft tissue calcification, premature atherosclerosis, rare or multiple neoplasms, malformed teeth, and flat feet. Diagnosis can be difficult due to the variable presentation and rarity of the disorder. Transmission is usually autosomal recessive. The WS gene, WRN, is member of the RecQ DNA helicase family. Biallelic mutations of WRN are responsible for most patients. Although heterozygous missense mutations in the LMNA gene have been observed in severely affected WS patients, this only accounts for a small fraction of non-WRN patients. Eighteen WS cases were referred to us for molecular analysis. Eleven had definite and three had probable WS according to the University of Washington Registry clinical criteria. All exons of the WRN gene and their splice junctions were sequenced. Of the fourteen definite or probable cases, 11 had one or more WRN mutation. Thirteen different mutations were found, and ten of these were previously undescribed. There were few phenotypic differences between patients with WRN mutation(s) and those who met clinical criteria though lacking WRN mutations. However, patients with mutations tended to have more symptoms overall, and mutations were not observed in the two cases with cardiomyopathy.
Kajino S, etal., J Neurol Sci. 2014 May 15;340(1-2):94-8. doi: 10.1016/j.jns.2014.02.036. Epub 2014 Mar 5.
A boy, who had shown muscle weakness and hypotonia from early childhood and fiber type disproportion (FTD) with no dystrophic changes on muscle biopsy, was initially diagnosed as having congenital fiber type disproportion (CFTD). Subsequently, he developed cardiac conduction blocks. We reconsidered
the diagnosis as possible LMNA-myopathy and found a heterozygous mutation in the LMNA gene. This encouraged us to search for LMNA mutations on 80 patients who met the diagnostic criteria of CFTD with unknown cause. Two patients including the above index case had heterozygous in-frame deletion mutations of c.367_369delAAG and c.99_101delGGA in LMNA, respectively. Four of 23 muscular dystrophy patients with LMNA mutation also showed fiber type disproportion (FTD). Importantly, all FTD associated with LMNA-myopathy were caused by hypertrophy of type 2 fibers as compared with age-matched controls, whereas CFTD with mutations in ACTA1 or TPM3 showed selective type 1 fiber atrophy but no type 2 fiber hypertrophy. Although FTD is not a constant pathological feature of LMNA-myopathy, we should consider the possibility of LMNA-myopathy whenever a diagnosis of CFTD is made and take steps to prevent cardiac insufficiency.
Hypoplasia of the aorta is a rare entity comprising tubular hypotrophy of a large segment of the thoracic and the abdominal aorta. We report for the first time the case of a 26-year-old man with Emery-Dreifuss muscular dystrophy presenting severe and diffuse hypoplasia of the aorta.
Lee JM, etal., J Clin Invest. 2016 Apr 1;126(4):1592-602. doi: 10.1172/JCI85908. Epub 2016 Mar 21.
The alternatively spliced products of LMNA, lamin C and prelamin A (the precursor to lamin A), are produced in similar amounts in most tissues and have largely redundant functions. This redundancy suggests that diseases, such as Hutchinson-Gilford progeria syndr
ome (HGPS), that are caused by prelamin A-specific mutations could be treated by shifting the output of LMNA more toward lamin C. Here, we investigated mechanisms that regulate LMNA mRNA alternative splicing and assessed the feasibility of reducing prelamin A expression in vivo. We identified an exon 11 antisense oligonucleotide (ASO) that increased lamin C production at the expense of prelamin A when transfected into mouse and human fibroblasts. The same ASO also reduced the expression of progerin, the mutant prelamin A protein in HGPS, in fibroblasts derived from patients with HGPS. Mechanistic studies revealed that the exon 11 sequences contain binding sites for serine/arginine-rich splicing factor 2 (SRSF2), and SRSF2 knockdown lowered lamin A production in cells and in murine tissues. Moreover, administration of the exon 11 ASO reduced lamin A expression in wild-type mice and progerin expression in an HGPS mouse model. Together, these studies identify ASO-mediated reduction of prelamin A as a potential strategy to treat prelamin A-specific diseases.
Garg A, etal., J Clin Endocrinol Metab. 2009 Dec;94(12):4971-83. doi: 10.1210/jc.2009-0472. Epub 2009 Oct 29.
CONTEXT: Hutchinson-Gilford progeria syndrome (HGPS) and mandibuloacral dysplasia are well-recognized allelic autosomal dominant and recessive progeroid disorders, respectively, due to mutations in lamin A/C (LMNA) gene. Heterozygous LMNA
;'>LMNA mutations have also been reported in a small number of patients with a less well-characterized atypical progeroid syndrome (APS). OBJECTIVE: The objective of the study was to investigate the underlying genetic and molecular basis of the phenotype of patients presenting with APS. RESULTS: We report 11 patients with APS from nine families, many with novel heterozygous missense LMNA mutations, such as, P4R, E111K, D136H, E159K, and C588R. These and previously reported patients now reveal a spectrum of clinical features including progeroid manifestations such as short stature, beaked nose, premature graying, partial alopecia, high-pitched voice, skin atrophy over the hands and feet, partial and generalized lipodystrophy with metabolic complications, and skeletal anomalies such as mandibular hypoplasia and mild acroosteolysis. Skin fibroblasts from these patients when assessed for lamin A/C expression using epifluorescence microscopy revealed variable nuclear morphological abnormalities similar to those observed in patients with HGPS. However, these nuclear abnormalities in APS patients could not be rescued with 48 h treatment with farnesyl transferase inhibitors, geranylgeranyl transferase inhibitors or trichostatin-A, a histone deacetylase inhibitor. Immunoblots of cell lysates from fibroblasts did not reveal prelamin A accumulation in any of these patients. CONCLUSIONS: APS patients have a few overlapping but some distinct clinical features as compared with HGPS and mandibuloacral dysplasia. The pathogenesis of clinical manifestations in APS patients seems not to be related to accumulation of mutant farnesylated prelamin A.
Quijano-Roy S, etal., Ann Neurol. 2008 Aug;64(2):177-86. doi: 10.1002/ana.21417.
OBJECTIVE: To describe a new entity of congenital muscular dystrophies caused by de novo LMNA mutations. METHODS: Fifteen patients presenting with a myopathy of onset in the first year of life were subjected to neurological and genetic evaluation. Histopatholog
ical and immunohistochemical analyses were performed for all patients. RESULTS: The 15 patients presented with muscle weakness in the first year of life, and all had de novo heterozygous LMNA mutations. Three of them had severe early-onset disease, no motor development, and the rest experienced development of a "dropped head" syndrome phenotype. Despite variable severity, there was a consistent clinical pattern. Patients typically presented with selective axial weakness and wasting of the cervicoaxial muscles. Limb involvement was predominantly proximal in upper extremities and distal in lower extremities. Talipes feet and a rigid spine with thoracic lordosis developed early. Proximal contractures appeared later, most often in lower limbs, sparing the elbows. Ten children required ventilatory support, three continuously through tracheotomy. Cardiac arrhythmias were observed in four of the oldest patients but were symptomatic only in one. Creatine kinase levels were mild to moderately increased. Muscle biopsies showed dystrophic changes in nine children and nonspecific myopathic changes in the remaining. Markedly atrophic fibers were common, most often type 1, and a few patients showed positive inflammatory markers. INTERPRETATION: The LMNA mutations identified appear to correlate with a relatively severe phenotype. Our results further broaden the spectrum of laminopathies and define a new disease entity that we suggest is best classified as a congenital muscular dystrophy (LMNA-related congenital muscular dystrophy, or L-CMD).
Bai S, etal., Case Rep Genet. 2014;2014:508231. doi: 10.1155/2014/508231. Epub 2014 Feb 3.
Mandibuloacral dysplasia (MAD) is a rare autosomal recessive disorder characterized by postnatal growth retardation, craniofacial anomalies, skeletal malformations, and mottled cutaneous pigmentation. Hutchinson-Gilford Progeria Syndrome (HGPS) is characterized by the clinical features of accelerate
d aging in childhood. Both MAD and HGPS can be caused by mutations in the LMNA gene. In this study, we describe a 2-year-old boy with overlapping features of MAD and HGPS. Mutation analysis of the LMNA gene revealed a homozygous missense change, p.M540T, while only the mother carries the mutation. Uniparental disomy (UPD) analysis for chromosome 1 showed the presence of maternal UPD. Markers in the 1q21.3-q22 region flanking the LMNA locus were isodisomic, while markers in the short arm and distal 1q region were heterodisomic. These results suggest that nondisjunction in maternal meiosis followed by loss of the paternal chromosome 1 during trisomy rescue might result in the UPD1 and homozygosity for the p.M540T mutation observed in this patient.
A and C [lamin A/C]) maps to chromosome 1q21 and has been associated with five distinct pathologies, including Dunnigan-type familial partial lipodystrophy, a condition that is characterized by subcutaneous fat loss and is invariably associated with insulin resistance and diabetes. Since patients with MAD frequently have partial lipodystrophy and insulin resistance, we hypothesized that the disease may be caused by mutations in the LMNA gene. We analyzed five consanguineous Italian families and demonstrated linkage of MAD to chromosome 1q21, by use of homozygosity mapping. We then sequenced the LMNA gene and identified a homozygous missense mutation (R527H) that was shared by all affected patients. Patient skin fibroblasts showed nuclei that presented abnormal lamin A/C distribution and a dysmorphic envelope, thus demonstrating the pathogenic effect of the R527H LMNA mutation.
Depreux FF, etal., Hum Mol Genet. 2015 Aug 1;24(15):4284-95. doi: 10.1093/hmg/ddv160. Epub 2015 May 6.
The nuclear face of the nuclear membrane is enriched with the intermediate filament protein lamin A. Mutations in LMNA, the gene encoding lamin A, lead to a diverse set of inherited conditions including myopathies that affect both the heart and skeletal muscle.
To gain insight about lamin A protein interactions, binding proteins associated with the tail of lamin A were characterized. Of 130 nuclear proteins found associated with the lamin A tail, 17 (13%) were previously described lamin A binding partners. One protein not previously linked to lamin A, matrin-3, was selected for further study, because like LMNA mutations, matrin-3 has also been implicated in inherited myopathy. Matrin-3 binds RNA and DNA and is a nucleoplasmic protein originally identified from the insoluble nuclear fraction, referred to as the nuclear matrix. Anti-matrin-3 antibodies were found to co-immunoprecipitate lamin A, and the lamin-A binding domain was mapped to the carboxy-terminal half of matrin-3. Three-dimensional mapping of the lamin A-matrin-3 interface showed that the LMNA truncating mutation Delta303, which lacks the matrin-3 binding domain, was associated with an increased distance between lamin A and matrin-3. LMNA mutant cells are known to have altered biophysical properties and the matrin-3-lamin A interface is positioned to contribute to these defects.
Wang H, etal., Zhonghua Xin Xue Guan Bing Za Zhi. 2005 Oct;33(10):875-9.
OBJECTIVE: To examine the function of the novel mutation E82K in LMNA gene identified in a Chinese family infected by dilated cardiomyopathy. METHODS: (1) One Chinese family infected by dilated cardiomyopathy was chosen for the study. Exons
1-12 of the LMNA gene were screened with both PCR method and the cycle sequencing of the PCR products. (2) cDNA of the E82K mutation or wild type of LMNA gene was transfected into HEK293 cells and the apoptosis of the cells was detected after treatment with 0.8 mmol/L H2O2. RESULTS: (1) A new mutation E82K in LMNA gene was identified in this dilated cardiomyopathy family. (2) Apoptosis was more in the HEK293 cells transfected with E82K mutation than those with empty vector or wild type LMNA gene. CONCLUSIONS: The missense mutation E82K in LMNA gene changed the polar of the amino acid. It showed a malignant phenotype of severe clinical symptoms, early onset, poor survival prognosis and might be associated with atrioventricular conduction block (II degrees-III degrees), suggesting that the E82K mutation in LMNA gene may be a candidate for nosogenesis of dilated cardiomyopathy.
INTRODUCTION: Mutations in the lamin A/C protein cause laminopathies, a heterogeneous group of disorders that include recessive axonal neuropathy (CMT2B1), Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy (LGMD), dilated cardiomyopathy with conduction defect, and d
ifferent forms of lipodystrophy and progeria. METHODS: We provide clinical, histopathological, muscle imaging, and cardiac features of a family with heterozygous mutation in the LMNA gene. RESULTS: We identified heterozygous mutations (c.80C> T; pT27I) in the LMNA gene in 3 family members who had the LGMD phenotype with onset in their early thirties and cardiac conduction defects or dilated cardiomyopathy. Interestingly, muscle biopsies showed changes consistent with fiber type disproportion (FTD). CONCLUSIONS: Fiber type disproportion has been reported only anecdotally in muscle biopsies of patients with LMNA mutations. Our report further supports this association and suggests inclusion of molecular testing for LMNA in the differential diagnosis of myopathies with FTD due to the risk for life threatening events.
OBJECTIVE: Mutations in LMNA have been linked to diverse disorders called laminopathies, which display heterogeneous phenotypes and include diseases affecting muscles, axonal neurons, progeroid syndromes, and lipodystrophies. Among the lipodystrophies, LMNA
le='font-weight:700;'>LMNA mutations have been reported most frequently in patients with familial partial lipodystrophy (FPLD) of the Dunnigan variety; however, phenotypic heterogeneity in the pattern of body fat loss has been observed. In this study, we searched for LMNA mutations in patients with various forms of lipodystrophy. DESIGN AND METHODS: We studied 21 unrelated individuals with lipodystrophy. Subjects underwent a complete clinical evaluation and were classified as typical FPLD (n=12), atypical partial lipodystrophy (n=7), or generalized lipodystrophy (n=2). Molecular analysis of LMNA gene, analysis of body fat by dual-energy X-ray absorptiometry, and biochemical measurements were performed. RESULTS: ALL PATIENTS WITH TYPICAL FPLD WERE FOUND TO CARRY LMNA MUTATIONS: seven patients harbored the heterozygous p.R482W (c.1444C>T), two patients harbored the p.R482Q (c.1445G>A), and two individuals harbored the novel heterozygous variant p.N466D (c.1396A>G), all in exon 8. Also, a homozygous p.R584H (c.1751 G>A) mutation in exon 11 was found. Among patients with atypical partial lipodystrophy, two of them were found to have LMNA mutations: a novel heterozygous p.R582C variation (c.1744 C>T) in exon 11 and a heterozygous substitution p.R349W (c.1045C>T) in exon 6. Among patients with generalized lipodystrophy, only one harbored LMNA mutation, a heterozygous p.T10I (c.29C>T) in exon 1. CONCLUSIONS: We have identified LMNA mutations in phenotypically diverse lipodystrophies. Also, our study broadens the spectrum of LMNA mutations in lipodystrophy.
Identifying the mutated gene that produces a particular muscle dystrophy is difficult because different genotypes may share a phenotype and vice versa. Muscle MRI is a useful tool to recognize patterns of muscle involvement in patients with muscle dystrophies and to guide the diagnosis process. The
radiologic pattern of muscle involvement in patients with mutations in the EMD and LMNA genes has not been completely established. Our objective is to describe the pattern of muscle fatty infiltration in patients with mutations in the EMD and in the LMNA genes and to search for differences between the two genotypes that could be helpful to guide the genetic tests. We conducted a national multicenter study in 42 patients, 10 with mutations in the EMD gene and 32 with mutations in the LMNA gene. MRI or CT was used to study the muscles from trunk to legs. Patients had a similar pattern of fatty infiltration regardless of whether they had the mutation in the EMD or LMNA gene. The main muscles involved were the paravertebral, glutei, quadriceps, biceps, semitendinosus, semimembranosus, adductor major, soleus, and gastrocnemius. Involvement of peroneus muscle, which was more frequently affected in patients with mutations in the EMD gene, was useful to differentiate between the two genotypes. Muscle MRI/CT identifies a similar pattern of muscle fatty infiltration in patients with mutations in the EMD or the LMNA genes. The involvement of peroneus muscles could be useful to conduct genetic analysis in patients with an EDMD phenotype.
Yassaee VR, etal., Gene. 2016 Feb 10;577(1):8-13. doi: 10.1016/j.gene.2015.08.071. Epub 2015 Nov 19.
Mandibuloacral dysplasia with type A lipodystrophy (MADA) is a rare genetic disorder inherited in an autosomal recessive fashion characterized by hypoplasia of the mandible and clavicles, acroosteolysis and lipodystrophy due to mutations in the LMNA or ZMPSTE2
4 genes. In the current study, we have investigated a consanguineous family clinically diagnosed with mandibuloacral dysplasia type A having an affected child for the LMNA gene alteration(s). Mother is now 15weeks pregnant, seeking advice on the health of her fetus. Peripheral blood was obtained from all family members after informed consent was achieved. Genomic DNA was isolated. The sequence of the LMNA gene, including all exons and intron boundaries was analyzed by PCR and Sanger sequencing. Chorionic villus was collected from the placenta to reveal the condition of the fetus. Molecular analysis ascertained a homozygous mutation c.1620G>A (p.M540I) in the proband and heterozygous alteration in the family. Genomic DNA isolated from the CVS was amplified using specific primers for identified deleterious mutation and analyzed by Sanger sequencing. Two pathogenic mutations c.1620G>A and c.1698C>T were identified in the fetus. Genetic counseling as well as justified rapid and sensitive genetic testing can provide reassurance for the families to prevent the high burden of genetic disorders. We have also applied several online tools including PolyPhen2, MUpro, SIFT, PoPMuSiC, Project HOPE and Mutation Taster to predict the impact of p.Met540Ile substitution as a hotspot region within LMNA. All tools showed reduction in the stability of the protein structure. We conclude that p.M540I mutation may causes disease in the homozygous state.
Brauch KM, etal., Am J Cardiol. 2009 May 15;103(10):1426-8. doi: 10.1016/j.amjcard.2009.01.354. Epub 2009 Apr 1.
Atrial fibrillation (AF) is a heritable, genetically heterogeneous disorder. To identify gene defects that cause or confer susceptibility to AF, a cohort of 268 unrelated patients with idiopathic forms of familial and sporadic AF was recruited. LMNA, encoding t
he nuclear membrane proteins, lamin A/C, was selected as a candidate gene for lone AF based on its established association with a syndrome of dilated cardiomyopathy, conduction system disease, and AF. Comprehensive mutation scanning identified only 1 potentially pathogenic mutation. In conclusion, LMNA mutations rarely cause lone AF and routine genetic testing of LMNA in these patients does not appear warranted.
Mitsuhashi H, etal., J Cell Sci. 2010 Nov 15;123(Pt 22):3893-900. doi: 10.1242/jcs.072157. Epub 2010 Oct 27.
Mutations in LMNA, which encodes A-type nuclear lamins, cause various human diseases, including myopathy, cardiomyopathy, lipodystrophy and progeria syndrome. To date, little is known about how mutations in a single gene cause a wide variety of diseases. Here, b
y characterizing an antibody that specifically recognizes the phosphorylation of Ser458 of A-type lamins, we uncover findings that might contribute to our understanding of laminopathies. This antibody only reacts with nuclei in muscle biopsies from myopathy patients with mutations in the Ig-fold motif of A-type lamins. Ser458 phosphorylation is not seen in muscles from control patients or patients with any other neuromuscular diseases. In vitro analysis confirmed that only lamin A mutants associated with myopathy induce phosphorylation of Ser458, whereas lipodystrophy- or progeria-associated mutants do not. We also found that Akt1 directly phosphorylates Ser458 of lamin A with myopathy-related mutations in vitro. These results suggest that Ser458 phosphorylation of A-type lamins correlates with striated muscle laminopathies; this might be useful for the early diagnosis of LMNA-associated myopathies. We propose that disease-specific phosphorylation of A-type lamins by Akt1 contributes to myopathy caused by LMNA mutations.
Lipatrophic diabetes, also referred to as familial partial lipodystrophy, is a rare disease that is metabolically characterized by hypertriglyceridemia and insulin resistance. Affected patients typically present with regional loss of body fat and muscular hypertrophic appearance. Variable symptoms m
ay comprise pancreatitis and/or eruptive xanthomas due to severe hypertriglyceridemia, acanthosis nigricans, polycystic ovaria, and carpal tunnel syndrome. Mutations within the LMNA gene on chromosome 1q21.2 were recently reported to result in the phenotype of familial partial lipodystrophy. The genetic trait is autosomal dominant. We identified a family with partial lipodystrophy carrying the R482W (Arg(482)Trp) missense mutation within LMNA. Here we present the lipoprotein characteristics in this family in detail. Clinically, the loss of sc fat and muscular hypertrophy especially of the lower extremities started as early as in childhood. Acanthosis and severe hypertriglyceridemia developed later in life, followed by diabetes. The characterization of the lipoprotein subfractions revealed that affected children present with hyperlipidemia. The presence and severity of hyperlipidemia seem to be influenced by age, apolipoprotein E genotype, and the coexistence of diabetes mellitus. In conclusion, dyslipemia is an early and prominent feature in the presented lipodystrophic family carrying the R482W mutation within LMNA.
Rudnik-Schoneborn S, etal., Neurogenetics. 2007 Apr;8(2):137-42. Epub 2006 Nov 29.
The molecular basis of autosomal dominant spinal muscular atrophy (AD-SMA) is largely unknown. Because the phenotypic spectrum of diseases caused by LMNA mutations is extremely broad and includes myopathies, neuropathies, and cardiomyopathies designated as class
1 laminopathies, we sequenced the LMNA gene in index patients with the clinical picture of proximal SMA, who had a family history suggestive of autosomal dominant inheritance. Among the 19 families investigated, two showed pathogenic mutations of the LMNA gene, resulting in the diagnosis of a class 1 laminopathy in about 10% of our series. We found one novel truncating mutation (c.1477C > T, Q493X) and one previously described missense mutation (c.1130G > T, R377H) in the LMNA gene of two unrelated patients with adult-onset proximal SMA followed by cardiac involvement 14 and 22 years after the onset of weakness. The pedigrees of both families revealed a high frequency of cardiac abnormalities or sudden deaths. Our findings extend the spectrum of laminopathies and are of relevance for genetic counseling and clinical care of families presenting with adult-onset proximal SMA. Particularly, if neurogenic atrophy is combined with a cardiac disease in a family, this should prompt LMNA mutation analysis.
Millat G, etal., Clin Biochem. 2009 Jun;42(9):892-8. doi: 10.1016/j.clinbiochem.2009.01.016. Epub 2009 Feb 6.
OBJECTIVES: LMNA mutations lead to a wide spectrum of disorders now called laminopathies. Due to large cohorts to investigate, mutational screening must be performed using an extremely sensitive and specific scanning method. DESIGN AND METHODS: High Resolution
Melting (HRM) analysis was developed for LMNA mutation detection. A cohort of 64 patients with dilated cardiomyopathy was prospectively screened using both HRM and DHPLC methodologies. RESULTS: All gene variants detected by DHPLC or by direct sequencing were also readily identified as abnormal by HRM analysis. Mutations were identified in 7 patients (approximately 11%). Complete molecular LMNA investigation was completed two times faster and cheaper than using DHPLC strategy. CONCLUSIONS: HRM analysis represents an inexpensive, highly sensitive and high-throughput method to identify LMNA genetic variants. The discovery of novel LMNA mutations will provide new insights into the pathophysiology of dilated cardiomyopathy and in all other laminopathies.
BACKGROUND: Congenital muscular dystrophy is a clinically and genetically heterogeneous group of myopathies. Congenital muscular dystrophy related to lamin A/C is rare and characterized by early-onset hypotonia with axial muscle weakness typically presenting with a loss in motor acquisiti
ons within the first year of life and a dropped-head phenotype. METHODS: Here we report the clinical and histological characteristics of four unrelated Brazilian patients with dropped-head syndrome and mutations in the LMNA gene. RESULTS: All patients had previously described mutations (p.E358K, p.R249W, and p.N39S) and showed pronounced cervical muscle weakness, elevation of serum creatine kinase, dystrophic pattern on muscle biopsy, and respiratory insufficiency requiring ventilatory support. Three of the patients manifested cardiac arrhythmias, and one demonstrated a neuropathic pattern on nerve conduction study. CONCLUSION: Although lamin A/C--related congenital muscular dystrophy is a clinically distinct and recognizable phenotype, genotype/phenotype correlation, ability to anticipate onset of respiratory and cardiac involvement, and need for nutritional support remain difficult.
Recently, studies on the pathogenesis of dilated cardiomyopathy (DCM) have focused on the underlying molecular biology and the association between single nucleotide polymorphisms (SNPs) and disease. This study was designed to explore the association between the rs4641 SNP of the LMNA
ight:700;'>LMNA gene and DCM in order to identify a new gene locus related to DCM. Polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing were employed to detect and genotype rs4641 in 198 patients with DCM and 160 healthy controls. Genotype and allele frequencies were compared to discover their relationship and logistic regression was used to assess the risk of DCM associated with the polymorphic variants. In the DCM group, the frequencies of the TC and TT genotypes and the T allele of rs4641 were remarkably higher than those in the control group (P < 0.01). According to risk analysis, taking the CC genotype as a reference, both the TC and TT genotypes increased the risk of DCM pathogenesis, with OR (95%CI) values of 5.957 (2.903- 12.222) and 6.424 (2.156-19.141), respectively. Taking the C allele as the reference, presence of the T allele was found to increase DCM risk, with OR (95%CI) of 5.295 (3.121-8.983). These results suggested that the C to T mutation at the rs4641 locus of LMNA could enhance the risk of DCM, and that rs4641 represented a genetic susceptibility locus. Therefore, it was concluded that the LMNA rs4641 SNP was associated with DCM risk, which indicated that LMNA is a susceptibility gene for DCM.
Yang L, etal., PLoS One. 2013 Aug 20;8(8):e71850. doi: 10.1371/journal.pone.0071850. eCollection 2013.
BACKGROUND: In eukaryotes the genetic material is enclosed by a continuous membrane system, the nuclear envelope (NE). Along the NE specific proteins assemble to form meshworks and mutations in these proteins have been described in a group of human diseases called laminopathies. Laminopathies includ
e lipodystrophies, muscle and cardiac diseases as well as metabolic or progeroid syndromes. Most laminopathies are caused by mutations in the LMNAgene encoding lamins A/C. Together with Nesprins (Nuclear Envelope Spectrin Repeat Proteins) they are core components of the LINC complex (Linker of Nucleoskeleton and Cytoskeleton). The LINC complex connects the nucleoskeleton and the cytoskeleton and plays a role in the transfer of mechanically induced signals along the NE into the nucleus, and its components have been attributed functions in maintaining nuclear and cellular organization as well as signal transduction. RESULTS: Here we narrowed down the interaction sites between lamin A and Nesprin-2 to aa 403-425 in lamin A and aa 6146-6347 in Nesprin-2. Laminopathic mutations in and around the involved region of lamin A (R401C, G411D, G413C, V415I, R419C, L421P, R427G, Q432X) modulate the interaction with Nesprin-2 and this may contribute to the disease phenotype. The most notable mutation is the lamin A mutation Q432X that alters LINC complex protein assemblies and causes chromosomal and transcription factor rearrangements. CONCLUSION: Mutations in Nesprin-2 and lamin A are characterised by complex genotype phenotype relations. Our data show that each mutation in LMNAanalysed here has a distinct impact on the interaction among both proteins that substantially explains how distinct mutations in widely expressed genes lead to the formation of phenotypically different diseases.
Tan D, etal., PLoS One. 2015 Jun 22;10(6):e0129699. doi: 10.1371/journal.pone.0129699. eCollection 2015.
This study aimed to analyze the correlation between the phenotype and genotype of Chinese patients with early-onset lamin A (LMNA)-related muscular dystrophy (MD). The clinical and myopathological data of 21 Chinese pediatric patients with early-onset LMNA
e='font-weight:700;'>LMNA-related MD were collected and analyzed. LMNA gene mutation analysis was performed by direct sequencing of genomic DNA. Sublocalization of wild-type and mutant proteins were observed by immunofluorescence using cultured fibroblasts and human embryonic kidney 293 (HEK 293) cell. Seven patients were diagnosed with Emery-Dreifuss muscular dystrophy (EDMD) and 14 were diagnosed with LMNA-associated congenital muscular dystrophy (L-CMD). Four biopsy specimens from the L-CMD cases exhibited inflammatory changes. Abnormal nuclear morphology was observed with both transmission electron microscopy and lamin A/C staining. We identified 10 novel and nine known LMNA gene mutations in the 21 patients. Some mutations (c.91G>A, c.94_96delAAG, c.116A>G, c.745C>T, c.746G>A, and c.1580G>C) were well correlated with EDMD or L-CMD. LMNA-related MD has a common symptom triad of muscle weakness, joint contractures, and cardiac involvement, but the severity of symptoms and disease progression differ greatly. Inflammatory change in biopsied muscle is a characteristic of early-stage L-CMD. Phenotype-genotype analysis determines that some mutations are well correlated with LMNA-related MD.
Stallmeyer B, etal., Genet Test Mol Biomarkers. 2012 Jun;16(6):543-9. doi: 10.1089/gtmb.2011.0214. Epub 2012 Jan 6.
The lamin A/C proteins are major structural and functional components of the nuclear lamina. Mutations identified in LMNA encoding lamin A/C belong to the most frequently described causes for inherited forms of dilated cardiomyopathy (DCM). To elucidate the clin
ical characteristics of LMNA mutation carriers we performed genetic analysis of LMNA in 20 unrelated patients with DCM and cardiac conduction disease. In six small nuclear families heterozygous mutations in LMNA were identified. Two missense mutations led to the substitution of highly conserved amino acid residues within the rod domain of lamin A/C and four not-yet-described nonsense mutations cause the formation of predicted truncated lamin A/C missing parts of the tail domain. DCM was the most prominent clinical characteristic of the affected family members with a high degree of involvement of conduction system defects and less often accompanied by muscular dystrophy. The cardiac phenotype of the affected family members was severe and progressive with age, indicating the necessity for a genetic testing for LMNA mutations in patients with familial DCM and early onset of conduction disorders.
Rodriguez S and Eriksson M, PLoS One. 2011;6(9):e25472. doi: 10.1371/journal.pone.0025472. Epub 2011 Sep 29.
Today, there are at least a dozen different genetic disorders caused by mutations within the LMNA gene, and collectively, they are named laminopathies. Interestingly, the same mutation can cause phenotypes with different severities or even different disorders an
d might, in some cases, be asymptomatic. We hypothesized that one possible contributing mechanism for this phenotypic variability could be the existence of high and low expressing alleles in the LMNA locus. To investigate this hypothesis, we developed an allele-specific absolute quantification method for lamin A and lamin C transcripts using the polymorphic rs4641(C/T)LMNA coding SNP. The contribution of each allele to the total transcript level was investigated in nine informative human primary dermal fibroblast cultures from Hutchinson-Gilford progeria syndrome (HGPS) and unaffected controls. Our results show differential expression of the two alleles. The C allele is more frequently expressed and accounts for approximately 70% of the lamin A and lamin C transcripts. Analysis of samples from six patients with Hutchinson-Gilford progeria syndrome showed that the c.1824C>T, p.G608G mutation is located in both the C and the T allele, which might account for the variability in phenotype seen among HGPS patients. Our method should be useful for further studies of human samples with mutations in the LMNA gene and to increase the understanding of the link between genotype and phenotype in laminopathies.
Ben Yaou R, etal., Rev Neurol (Paris). 2005 Jan;161(1):42-54.
INTRODUCTION: Limb girdle muscular dystrophy type 1b (LGMD1B), due to LMNA gene mutations, is a relatively rare form of LGMD characterized by proximal muscle involvement associated with heart involvement comprising atrio-ventricular conduction blocks and dilated
cardiomyopathy. Its clinical and genetic diagnosis is crucial for cardiac management and genetic counselling. Seven LMNA mutations have been previously reported to be responsible for LGMD1B. PATIENTS AND METHODS: We describe the neurological and cardiologic features of 14 patients belonging to 8 families in whom we identified 6 different LMNA mutations, 4 of them having never been reported. Results. Eleven patients had an LGMD1B phenotype with scapulohumeral and pelvic-femoral involvement. Thirteen patients had cardiac disease associating conduction defects (12 patients) or arrhythmias (9 patients). Seven patients needed cardiac device (pacemaker or implantable cardiac defibrillator) and two had heart transplantation. CONCLUSION: This study allowed us to specify the clinical characteristics of this entity and to outline the first phenotype/genotype relations resulting from these observations.
Dadali EL, etal., Zh Nevrol Psikhiatr Im S S Korsakova. 2016;116(1):70-5.
OBJECTIVE: To study clinical/genetic characteristics of congenital muscular dystrophy caused by mutations in the LMNA gene in 5 patients from the Russian population. MATERIAL AND METHODS: DNA samples of 42 probands, aged from 2 months to 9 years, with character
istic signs of congenital muscular dystrophy from nonrelated families were studied. The diagnosis was based on the results of genealogical analysis, neurological examination, serum creatine phosphokinase activity, results of electroneuromyography. RESULTS AND CONCLUSION: In the Russian population, the frequency of congenital muscular dystrophy caused by mutations in the LMNA gene is not less than 12% of all cases of this group of diseases. The results indicate the presence of major mutation c.94_96delAAC in the LMNA gene. Specific phenotypic features of this form of congenital muscular dystrophy with symptoms of progressive flaccid paralysis with predominant lesions of axial muscles and plantar flexor muscles of the foot are described.
Wang H, etal., Zhonghua Xin Xue Guan Bing Za Zhi. 2007 Jan;35(1):21-3.
OBJECTIVE: To investigate the effect of a novel LMNA gene mutation E82K found in a Chinese family with dilated cardiomyopathy on cell cycle of HEK293 cells. METHODS: (1) Human wild type full-length LMNA
gene cDNA was subcloned into eukaryotic expression vector pTracer-CMV and point mutation was introduced into the cDNA. LMNA gene wild type and mutant E82K LMNA gene were transfected into HEK293 cells respectively and stable cell lines resistant to antibiotic were obtained 4 weeks later. (2) Cell cycle changes were analyzed by flow cytometry in HEK293 cells transfected with wild type and mutant E82K LMNA gene and empty vector in the presence of 0.8 mmol/L H(2)O(2). RESULTS: Cell circle was arrested at G0/G1 phase in the cells transfected with mutated E82K LMNA gene and at G2/M phase in other cell groups in the presence of H(2)O(2). CONCLUSION: Cell circle was arrested at G0/G1 phase in the cells transfected with E82K LMNA gene in the presence of H(2)O(2) in HEK293 cells.
Dunnigan-type familial partial lipodystrophy (FPLD) is a rare monogenic adipose tissue disorder in which the affected subjects have increased predisposition to insulin resistance and related metabolic complications, such as glucose intolerance, diabetes, dyslipidemia, and hepatic steatosis. Our pati
ent was a 35-year-old female who had been receiving insulin injection therapy for diabetes mellitus and was transferred to our hospital. She was diagnosed with FPLD on the basis of the following symptoms: increase in subcutaneous fat in the face, neck, and upper trunk; loss of subcutaneous fat in the lower limbs and the gluteal region. We found a heterozygous CGG to CAG transition in codon 482 of exon 8 in the gene encoding lamin A/C (LMNA), which leads to an arginine to glutamine substitution (R482Q). At the time of admission, her serum creatinine level was 8.4 mg/dl, and her blood urea nitrogen (BUN) level was 81 mg/dl. Her serum creatinine level was elevated and hemodialysis was performed twice every week. However, she died of cerebral hemorrhage 9 months after hemodialysis. Although it is uncommon for patients with FPLD to exhibit renal dysfunction and require hemodialysis, this case suggests the need for careful analysis of renal function in a patient with FPLD.
Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder normally caused by a spontaneous heterozygous mutation in the LMNA gene that codes for the nuclear lamina protein lamin A. Several enzymes are involved in the processing of its precur
sor, prelamin A, to the mature lamin A. A functional knockout of one of the enzymes involved in prelamin A processing, the zinc metalloprotease ZMPSTE24, causes an even more severe disorder with early neonatal death described as restrictive dermatopathy (RD). This work describes a HGPS patient with a combined defect of a homozygous loss-of-function mutation in the ZMPSTE24 gene and a heterozygous mutation in the LMNA gene that results in a C-terminal elongation of the final lamin A. Whereas the loss of function mutation of ZMPSTE24 normally results in lethal RD, the truncation of LMNA seems to be a salvage alteration alleviating the clinical picture to the HGPS phenotype. The mutations of our patient indicate that farnesylated prelamin A is the deleterious agent leading to the HGPS phenotype, which gives further insights into the pathophysiology of the disorder.
Kim HY, etal., Muscle Nerve. 2008 Oct;38(4):1336-9. doi: 10.1002/mus.21066.
We report the clinical characteristics, genetic analysis, and muscle biopsy findings of a family with Emery-Dreifuss muscular dystrophy and a novel mutation (Leu162Pro) in the LMNA gene. Within this single family, the age of onset and disease severity varied am
Mutations in LMNA, which encodes nuclear Lamins A and C cause diseases affecting various organs, including the heart. We have determined the effects of an Lmna H222P mutation on signaling pathways involved in the development
of cardiomyopathy in a knockin mouse model of autosomal dominant Emery-Dreifuss muscular dystrophy. Analysis of genome-wide expression profiles in hearts using Affymetrix GeneChips showed statistically significant differences in expression of genes in the MAPK pathways at the incipience of the development of clinical disease. Using real-time PCR, we showed that activation of MAPK pathways preceded clinical signs or detectable molecular markers of cardiomyopathy. In heart tissue and isolated cardiomyocytes, there was activation of MAPK cascades and downstream targets, implicated previously in the pathogenesis of cardiomyopathy. Expression of H222P Lamin A in cultured cells activated MAPKs and downstream target genes. Activation of MAPK signaling by mutant A-type lamins could be a cornerstone in the development of heart disease in autosomal dominant Emery-Dreifuss muscular dystrophy.
OBJECTIVE: The LMNA 1908C/T polymorphism has been reported to be associated with dyslipidaemia, metabolic syndrome, adipose tissue metabolism and obesity phenotypes, suggesting that this polymorphism presents an increased risk of atherosclerosis and vascular dis
eases. However, there have been no previous reports on the relationship between the LMNA 1908C/T polymorphism and vascular diseases. The aim of this study therefore was to investigate the association between the LMNA 1908C/T polymorphism and the prevalence of vascular disease in Japanese patients with type 2 diabetes. DESIGN: A cross-sectional, hospital-based study of diabetic complications with an LMNA gene background. PATIENTS: One hundred and sixty-six Japanese men with type 2 diabetes. Measurements LMNA 1908C/T polymorphism (by polymerase chain reaction restriction fragment length polymorphism, PCR-RFLP); diabetic retinopathy (by standard fundus photography); diabetic nephropathy (by urinary albumin excretion rate); diabetic neuropathy (by signs, symptoms and/or nerve conduction velocity); coronary heart disease (by symptoms of typical chest pain and/or history of myocardial infarction, and ischaemic electrocardiographic alteration and/or coronary artery bypass graft surgery); cerebral vascular disease (by ultrasonography, computed tomography and/or magnetic resonance imaging). RESULTS: Carriers of the LMNA 1908T allele manifested a significantly higher prevalence of diabetic nephropathy and cerebral vascular disease than carriers of the C allele. Multiple regression analysis showed that the LMNA 1908T allele tended to be associated with cerebral vascular disease, but was independent of age, hypertension, total cholesterol or triglyceride [odds ratio (OR) 7.03, P=0.0611]. Similarly, the LMNA 1908T allele showed a significant association with diabetic nephropathy, not independent of total cholesterol or triglyceride. CONCLUSIONS: The LMNA 1908C/T polymorphism plays an important role in the development of cerebral vascular disease and diabetic nephropathy in Japanese men with type 2 diabetes.
The present study aimed to examine and analyze cardiac involvement in two EmeryDreifuss muscular dystrophy (EDMD) pedigrees caused by the c.1583 C-->G mutation of the lamin A/C gene (LMNA). The clinical and genetic characteristics of members of two families with
EDMD were evaluated by performing neurological examinations, skeletal muscle biopsies, cardiac evaluations, including electrocardiography, 24 h Holter, ultrasound cardiography and 99TcMMIBIgated myocardiac perfusion imaging, and genomic DNA sequencing. Family history investigations revealed an autosomal dominant transmission pattern of the disease in Family 1 and a sporadic case in Family 2. The three affected patients exhibited typical clinical features of EDMD, including joint contractures, muscle weakness and cardiac involvement. Muscle histopathological investigation revealed dystrophic features. In addition, each affected individual exhibited either cardiac arrhythmia, which was evident as sinus tachycardia, atrial flutter or complete atrioventricular inhibition. Cardiac imaging revealed dilated cardiomyopathy in two of the individuals, one of whom was presented with heart failure. The second patient presented with no significant abnormalities in cardiac structure or function. The three affected individuals exhibited a heterozygous missense mutation in the LMNA gene (c.1583 C-->G), which caused a T528R amino acid change in the LMNA protein. In conclusion, the present study identified three patients with EDMD, exhibiting the same dominant LMNA mutation and presenting with a spectrum of severe cardiac abnormalities, including cardiac conduction system defects, cardiomyopathy and heart failure. As LMNA mutations have been associated with at least six clinical disorders, including EDMD, the results of the present study provide additional mutational and functional data, which may assist in further establishing LMNA mutational variation and disease pathogenesis.
Mutations in LMNA encoding lamin A and C proteins cause monogenic syndromes characterized by muscular dystrophy and familial partial lipodystrophy. Eight tag single nucleotide polymorphisms in the LMNA locus were genotyped i
n 7,495 Danish whites and related to metabolic and anthropometric traits. The minor T-allele of rs4641 was nominally associated with type 2 diabetes (odds ratio 1.14 [95% CI 1.03-1.26], P = 0.01) in a study of 1,324 type 2 diabetic patients and 4,386 glucose-tolerant subjects and with elevated fasting plasma glucose levels in a population-based study of 5,395 middle-aged individuals (P = 0.008). The minor T-allele of rs955383 showed nominal association with obesity in a study of 5,693 treatment-naive subjects (1.25 [1.07-1.64], P = 0.01), and after dichotomization of waist circumference, the minor alleles of rs955383 and rs11578696 were nominally associated with increased waist circumference (1.14 [1.04-1.23], P = 0.003; 1.12 [1.00-1.25], P = 0.04). The minor G-allele of rs577492 was associated with elevated fasting serum cholesterol and short stature (P = 3.0 . 10(-5) and P = 7.0 . 10(-4)). The findings are not corrected for multiple comparisons and are by nature exploratory. However, if replicated, these findings suggest that less severe variation in a gene locus known to harbor severe mutations causing monogenic syndromes may modestly increase susceptibility to common metabolic and anthropometrical phenotypes of polygenic origin.
CONTEXT: Mandibuloacral dysplasia type A (MADA; OMIM 248370) is a rare progeroid syndrome characterized by dysmorphic craniofacial and skeletal features, lipodystrophy, and metabolic complications. Most Italian patients carry the same homozygous missense mutation (p.R527H) in the C-termin
al tail domain of the LMNA gene, which encodes lamin A/C, an intermediate filament component of the nuclear envelope. OBJECTIVE: The objective of the study was to identify novel LMNA mutations in individuals with clinical characteristics (bird-like facies, mandibular and clavicular hypoplasia, acroosteolysis, lipodystrophy, alopecia) observed in other well-known patients. DESIGN: The LMNA gene was sequenced. Functional properties of the mutant alleles were investigated. PATIENT: We report a 27-yr-old Italian woman showing a MADA-like phenotype. Features include a hypoplastic mandible, acroosteolysis, pointed nose, partial loss of sc fat, and a progeric appearance. Due to the absence of clavicular dysplasia and normal metabolic profiles, generally associated with muscle hyposthenia and generalized hypotonia, this phenotype can be considered an atypical laminopathy. RESULTS: We identified a patient compound heterozygote for the p.R527H and p.V440M alleles. The patient's cells showed nuclear shape abnormalities, accumulation of pre-lamin A, and irregular lamina thickness. Lamins A and C showed normal expression and localization. The electron microscopy detected heterochromatin defects with a pattern similar to those observed in other laminopathies. However, chromatin analysis showed a normal distribution pattern of the major heterochromatin proteins: heterochromatin protein-1beta and histone H3 methylated at lysine 9. CONCLUSIONS: The clinical and cellular features of this patient show overlapping laminopathy phenotypes that could be due to the combination of p.R527H and p.V440M alleles.
Sun LP, etal., Chin Med J (Engl). 2010 Apr 20;123(8):1058-62.
BACKGROUND: Mutations in the lamin A/C gene (LMNA) may cause familial dilated cardiomyopathy (dilated cardiomyopathy) characterized by early onset atrio-ventricular block (A-V block) before the manifestation of dilated cardiomyopathy and high risk of sudden deat
h due to ventricular arrhythmia, which is very similar to the phenotype of gap junction related heart disease. This study aimed to determine the expression and localization of connexins in neonatal myocytes transfected with wild-type (WT) or mutant LMNA to elucidate how these mutations cause heart diseases. METHODS: We studied the connexin 43 (Cx43) and connexin 40 (Cx40) expression in cultured neonatal myocytes transfected with wild-type (WT) or mutant LMNA (Glu82Lys (E82K) and Arg644Cys (R644C)) using confocal imaging and Western blotting analysis. RESULTS: Cx43 protein expression was reduced by 40% in cells transfected with LMNA E82K than that in cells transfected with WT LMNA cDNA. Confocal imaging showed that the Cx43 located inside the cells by LMNA E82K. By contrast, LMNA E82K mutation had no effect on expression and localization of Cx40. LMNA R644C transfection did not show any significant effects on gap junctions at all. CONCLUSIONS: Our findings suggest that LMNA E82K significantly reduced the Cx43 expression and altered its localization which may be one of the pathological mechanisms underlying LMNA-related heart disease.
Besci O, etal., J Clin Endocrinol Metab. 2024 Feb 20;109(3):e1204-e1224. doi: 10.1210/clinem/dgad606.
CONTEXT: Lipodystrophy syndromes are a heterogeneous group of rare genetic or acquired disorders characterized by generalized or partial loss of adipose tissue. LMNA-related lipodystrophy syndromes are classified based on the severity and distribution
of adipose tissue loss. OBJECTIVE: We aimed to annotate all clinical and metabolic features of patients with lipodystrophy syndromes carrying pathogenic LMNA variants and assess potential genotype-phenotype relationships. METHODS: We retrospectively reviewed and analyzed all our cases (n = 115) and all published cases (n = 379) curated from 94 studies in the literature. RESULTS: The study included 494 patients. The most common variants in our study, R482Q and R482W, were associated with similar metabolic characteristics and complications though those with the R482W variant were younger (aged 33 [24] years vs 44 [25] years; P < .001), had an earlier diabetes diagnosis (aged 27 [18] vs 40 [17] years; P < .001) and had lower body mass index levels (24 [5] vs 25 [4]; P = .037). Dyslipidemia was the earliest biochemical evidence described in 83% of all patients at a median age of 26 (10) years, while diabetes was reported in 61% of cases. Among 39 patients with an episode of acute pancreatitis, the median age at acute pancreatitis diagnosis was 20 (17) years. Patients who were reported to have diabetes had 3.2 times, while those with hypertriglyceridemia had 12.0 times, the odds of having pancreatitis compared to those who did not. CONCLUSION: This study reports the largest number of patients with LMNA-related lipodystrophy syndromes to date. Our report helps to quantify the prevalence of the known and rare complications associated with different phenotypes and serves as a comprehensive catalog of all known cases.
Raffaele Di Barletta M, etal., Am J Hum Genet. 2000 Apr;66(4):1407-12. Epub 2000 Mar 16.
Emery-Dreifuss muscular dystrophy (EMD) is a condition characterized by the clinical triad of early-onset contractures, progressive weakness in humeroperoneal muscles, and cardiomyopathy with conduction block. The disease was described for the first time as an X-linked muscular dystrophy, but autoso
mal dominant and autosomal recessive forms were reported. The genes for X-linked EMD and autosomal dominant EMD (AD-EMD) were identified. We report here that heterozygote mutations in LMNA, the gene for AD-EMD, may cause diverse phenotypes ranging from typical EMD to no phenotypic effect. Our results show that LMNA mutations are also responsible for the recessive form of the disease. Our results give further support to the notion that different genetic forms of EMD have a common pathophysiological background. The distribution of the mutations in AD-EMD patients (in the tail and in the 2A rod domain) suggests that unique interactions between lamin A/C and other nuclear components exist that have an important role in cardiac and skeletal muscle function.
Saj M, etal., Int J Cardiol. 2010 Oct 29;144(3):e51-3. doi: 10.1016/j.ijcard.2008.12.083. Epub 2009 Jan 22.
In laminopathies cardiac involvement is common with dilated cardiomyopathy associated with atrio-ventricular block and malignant ventricular arrhythmia found in vast majority of patients. However, the specific disease course can be very different even among members of the same family which makes gen
otype-phenotype correlations difficult. Here we describe a 19-year-old patient with the LMNA R541C mutation and compare the course of his disease with two previously reported cases of the same molecular defect. We found that our patient shared important features with the previously described other subjects: significant LV segmental contractility defects (dyskinesis of the inferior wall and akinesis of LV apex), the presence of LBBB without atrio-ventricular block on 12-lead standard ECG and ICD requirement. The important differences between our subject and previously reported cases were early presentation (first symptoms at the age of 11 years) and early, progressive LV dilatation. We conclude that the LMNA R541C mutation should be considered not only in patients with malignant ventricular arrhythmia and LV local wall motion abnormalities, but also in classic dilated cardiomyopathy with profound segmental LV contractility defects.
Hegele RA, etal., Arterioscler Thromb Vasc Biol. 2003 Jan 1;23(1):111-6.
OBJECTIVE: Dunnigan-type familial partial lipodystrophy (FPLD) due to mutant LMNA is a monogenic form of insulin resistance. Affected subjects, especially women, are at increased risk of early coronary heart disease (CHD). Although common insulin resistance is a
ssociated with several biochemical perturbations, including elevated C-reactive protein (CRP), the biochemical profile in subjects with mutant LMNA is incompletely defined. METHODS AND RESULTS: We studied 35 nondiabetic adult FPLD subjects (of whom 24 were women) with either the LMNA R482Q or R482W missense mutations and 51 matched normal first-degree relatives (of whom 27 were women). Compared with normal controls, LMNA mutation carriers had significantly higher plasma insulin and more dyslipidemia, higher mean triglycerides and lower HDL cholesterol, significantly higher nonesterified free fatty acids and CRP, and significantly lower leptin and adiponectin than controls. Subgroup analyses showed that these differences were more pronounced in women. Other biomarkers such as resistin, fibrinogen, and plasminogen activator inhibitor-1 were not different between groups. CONCLUSIONS: LMNA mutations in nondiabetic patients with FPLD are associated with several metabolic and biochemical changes, particularly in women. The unfavorable profile might contribute to the increased susceptibility to CHD seen in LMNA mutation carriers.
Carboni N, etal., Muscle Nerve. 2010 Jan;41(1):85-91. doi: 10.1002/mus.21443.
The aim of this study is to report the evolution of a phenotype in members of a single family carrying the heterozygous exon 1 c.178 C/G, p.Arg 60 Gly LMNA gene mutation. All mutated family members underwent neurological and cardiological assessments for a peri
od ranging from 10 to 20 years. At onset, 4 affected adult members presented a phenotype that required pacemaker implantation. Three subjects underwent cardiac transplantation leading to long-term survival in 2 of them. One of the 3 longest surviving relatives manifested late lipodystrophy, and the other 2 had lipodystrophy, insulin-resistant diabetes, and distal peripheral neuropathy. The findings demonstrate that the exon 1 c.178 C/G, p.Arg 60 Gly LMNA gene mutation is associated with a novel phenotype featuring cardiac involvement followed by late lipodystrophy, diabetes, and peripheral axonal neuropathy.
Sebillon P, etal., J Med Genet. 2003 Aug;40(8):560-7.
AIMS: Mutations in the lamin A/C gene (LMNA) have been reported to be involved in dilated cardiomyopathy (DCM) associated with conduction system disease and/or skeletal myopathy. The aim of this study was to perform a mutational analysis of LMNA
ight:700;'>LMNA in a large white population of patients affected by dilated cardiomyopathy with or without associated symptoms. METHODS: We performed screening of the coding sequence of LMNA on DNA samples from 66 index cases, and carried out cell transfection experiments to examine the functional consequences of the mutations identified. RESULTS: A new missense (E161K) mutation was identified in a family with early atrial fibrillation and a previously described (R377H) mutation in another family with a quadriceps myopathy associated with DCM. A new mutation (28insA) leading to a premature stop codon was identified in a family affected by DCM with conduction defects. No mutation in LMNA was found in cases with isolated dilated cardiomyopathy. Functional analyses have identified potential physiopathological mechanisms involving identified mutations, such as haploinsufficiency (28insA) or intermediate filament disorganisation (E161K, R377H). CONCLUSION: For the first time, a specific phenotype characterised by early atrial fibrillation is associated with LMNA mutation. Conversely, mutations in LMNA appear as a rare cause of isolated dilated cardiomyopathy. The variable phenotypes observed in LMNA-DCM might be explained by the variability of functional consequences of LMNA mutations.
Mounkes LC, etal., Hum Mol Genet. 2005 Aug 1;14(15):2167-80. Epub 2005 Jun 22.
The nuclear lamina is an approximately 10 nm thick proteinaceous layer underlying the inner nuclear membrane. The A-type lamins, nuclear intermediate filament proteins encoded by the LMNA gene, are basic components of the nuclear lamina. Mutations in LMNA
='font-weight:700;'>LMNA are associated with the laminopathies, congenital diseases affecting tissue regeneration and homeostasis. One of these laminopathies associated with missense mutations in LMNA is dilated cardiomyopathy with conduction system disease (DCM-CD1). To understand how the laminopathies arise from different mutations in a single gene, we derived a mouse line by homologous recombination expressing the Lmna-N195K variant of the A-type lamins with an asparagine-to-lysine substitution at amino acid 195, which causes DCM in humans. This mouse line shows characteristics consistent with DCM-CD1. Continuous electrocardiographic monitoring of cardiac activity demonstrated that LmnaN195K/N195K mice die at an early age due to arrhythmia. By immunofluorescence and western analysis, the transcription factor Hf1b/Sp4 and the gap junction proteins connexin 40 and connexin 43 were misexpressed and/or mislocalized in LmnaN195K/N195K hearts. Desmin staining revealed a loss of organization at sarcomeres and intercalated disks. Mutations within the LMNA gene may therefore cause cardiomyopathy by disrupting the internal organization of the cardiomyocyte and/or altering the expression of transcription factors essential to normal cardiac development, aging or function.
Hamadouche T, etal., Ann Hum Genet. 2008 Sep;72(Pt 5):590-7. doi: 10.1111/j.1469-1809.2008.00456.x. Epub 2008 Jun 6.
CMT2B1, an axonal subtype (MIM 605588) of the Charcot-Marie-Tooth disease, is an autosomal recessive motor and sensory neuropathy characterized by progressive muscular and sensory loss in the distal extremities with chronic distal weakness. The genetic defect associated with the disease is, to date
, a unique homozygous missense mutation, p.Arg298Cys (c.892C>T), in the LMNA gene. So far, this mutation has only been found in affected individuals originating from a restricted region of North Western Africa (northwest of Algeria and east of Morocco), strongly suggesting a founder effect. In order to address this hypothesis, genotyping of both STRs and intragenic SNPs was performed at the LMNA locus, at chromosome 1q21.2-q21.3, in 42 individuals affected with CMT2B1 from 25 Algerian families. Our results indicate that the affected individuals share a common ancestral haplotype in a region of about 1.0 Mb (1 cM) and that the most recent common ancestor would have lived about 800-900 years ago (95% confidence interval: 550 to 1300 years).
Fong LG, etal., Proc Natl Acad Sci U S A. 2004 Dec 28;101(52):18111-6. Epub 2004 Dec 17.
Zmpste24 is a metalloproteinase required for the processing of prelamin A to lamin A, a structural component of the nuclear lamina. Zmpste24 deficiency results in the accumulation of prelamin A within cells, a complete loss of mature lamin A, and misshapen nuclear envelopes. Zmpste24-deficient (Zmps
te24(-/-)) mice exhibit retarded growth, alopecia, micrognathia, dental abnormalities, osteolytic lesions in bones, and osteoporosis, which are phenotypes shared with Hutchinson-Gilford progeria syndrome, a human disease caused by the synthesis of a mutant prelamin A that cannot undergo processing to lamin A. Zmpste24(-/-) mice also develop muscle weakness. We hypothesized that prelamin A might be toxic and that its accumulation in Zmpste24(-/-) mice is responsible for all of the disease phenotypes. We further hypothesized that Zmpste24(-/-) mice with half-normal levels of prelamin A (Zmpste24(-/-) mice with one Lmna knockout allele) would be subjected to less toxicity and be protected from disease. Thus, we bred and analyzed Zmpste24(-/-)Lmna(+/-) mice. As expected, prelamin A levels in Zmpste24(-/-)Lmna(+/-) cells were significantly reduced. Zmpste24(-/-)Lmna(+/-) mice were entirely normal, lacking all disease phenotypes, and misshapen nuclei were less frequent in Zmpste24(-/-)Lmna(+/-) cells than in Zmpste24(-/-) cells. These data suggest that prelamin A is toxic and that reducing its levels by as little as 50% provides striking protection from disease.
van Tintelen JP, etal., Am Heart J. 2007 Dec;154(6):1130-9. Epub 2007 Sep 14.
BACKGROUND: Among the most frequently encountered mutations in dilated cardiomyopathy (DCM) are those in the lamin A/C (LMNA) gene. Our goal was to analyze the LMNA gene in patients with DCM and/or conduction disease referre
d to the cardiogenetics outpatient clinic and to evaluate the prevalence of LMNA mutations and their clinical expression. METHODS AND RESULTS: The LMNA gene was screened in 61 index patients. Eleven mutations (including 6 novel) were identified, mainly in the subgroup of familial DCM with cardiac conduction disease (3/10 index patients) and in patients with DCM and Emery-Dreifuss, Limb-Girdle, or unclassified forms of muscular dystrophy (7/8 index patients). In addition, a mutation was identified in 1 of 4 families with only cardiac conduction disease. We did not identify any large deletions or duplications. Genotype-phenotype relationships revealed a high rate of sudden death and cardiac transplants in carriers of the p.N195K mutation. Our study confirmed that the p.R225X mutation leads to cardiac conduction disease with late or no development of DCM, underscoring the importance of this mutation in putative familial "lone conduction disease." Nearly one third of LMNA mutation carriers had experienced a thromboembolic event. CONCLUSIONS: This study highlights the role of LMNA mutations in DCM and related disorders. A severe phenotype in p.N195K mutation carriers and preferential cardiac conduction disease in p.R225X carriers was encountered. Because of the clinical variability, including the development of associated symptoms in time, LMNA screening should be considered in patients with DCM or familial lone conduction disease.
OBJECTIVES: Type 2 familial partial lipodystrophy (FPLD2) is a rare adipose tissue (AT) disease caused by mutations in LMNA, in which lipomas appear occasionally. In this study, we aimed to histologically characterize FPLD2-associated lipomatosis and study the e
xpression of genes and proteins involved in cell cycle control, mitochondrial function, inflammation and adipogenesis. DESIGN AND PATIENTS: One lipoma and perilipoma fat from each of four subjects with FPLD2 and 10 control subjects were analysed by optical microscopy. The presence of inflammatory cells was evaluated by immunohistochemistry. Real-time RT-PCR and Western blot were used to evaluate gene and protein levels. RESULTS: Adipocytes from lipodystrophic patients were significantly larger than those of controls, in both the lipomas and perilipoma fat. Lipodystrophic AT exhibited CD68(+) macrophages and CD3(+) lymphocytes infiltration. TP53 expression was reduced in all types of lipomas. At protein level, C/EBPbeta, p53 and pRb were severely disturbed in both lipodystrophic lipomas and perilipoma fat coming from lipoatrophic areas, whereas the expression of CEBPalpha was normal. Mitochondrial function genes were less expressed in lipoatrophic fat. In both lipomas and perilipoma fat from lipoatrophic areas, the expression of adipogenes was lower than controls. CONCLUSIONS: Even in lipomas, the adipogenic machinery is impaired in lipodystrophic fat coming from lipoatrophic regions in FPLD2, although the histological phenotype is near-normal, exhibiting low-grade inflammatory features. Our results suggest that the p53 pathway and some adipogenic proteins, such as CEBPalpha, could contribute to the maintenance of this near normal phenotype in the remnant AT present in these patients.
De Sandre-Giovannoli A, etal., Am J Hum Genet. 2002 Mar;70(3):726-36. doi: 10.1086/339274. Epub 2002 Jan 17.
The Charcot-Marie-Tooth (CMT) disorders comprise a group of clinically and genetically heterogeneous hereditary motor and sensory neuropathies, which are mainly characterized by muscle weakness and wasting, foot deformities, and electrophysiological, as well as histological, changes. A subtype, CMT2
, is defined by a slight or absent reduction of nerve-conduction velocities together with the loss of large myelinated fibers and axonal degeneration. CMT2 phenotypes are also characterized by a large genetic heterogeneity, although only two genes---NF-L and KIF1Bbeta---have been identified to date. Homozygosity mapping in inbred Algerian families with autosomal recessive CMT2 (AR-CMT2) provided evidence of linkage to chromosome 1q21.2-q21.3 in two families (Zmax=4.14). All patients shared a common homozygous ancestral haplotype that was suggestive of a founder mutation as the cause of the phenotype. A unique homozygous mutation in LMNA (which encodes lamin A/C, a component of the nuclear envelope) was identified in all affected members and in additional patients with CMT2 from a third, unrelated family. Ultrastructural exploration of sciatic nerves of LMNA null (i.e., -/-) mice was performed and revealed a strong reduction of axon density, axonal enlargement, and the presence of nonmyelinated axons, all of which were highly similar to the phenotypes of human peripheral axonopathies. The finding of site-specific amino acid substitutions in limb-girdle muscular dystrophy type 1B, autosomal dominant Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy type 1A, autosomal dominant partial lipodystrophy, and, now, AR-CMT2 suggests the existence of distinct functional domains in lamin A/C that are essential for the maintenance and integrity of different cell lineages. To our knowledge, this report constitutes the first evidence of the recessive inheritance of a mutation that causes CMT2; additionally, we suggest that mutations in LMNA may also be the cause of the genetically overlapping disorder CMT2B1.
Mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found to cause at least four different kinds of genetic disorders: autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD2; MIM 181350); limb-girdle muscular dystrophy type
1B (LGMD1B; MIM 159001); dilated cardiomyopathy type 1A (CMD1A; MIM 115200); and familial partial lipodystrophy (FPLD; MIM 151660). Recently, we have studied two Korean patients with atrioventricular conduction defects. They had variable extents of muscular dystrophy; one patient was diagnosed with EDMD2 and the other with LGMD1B. We performed a mutation analysis of the LMNA gene by direct sequencing and found two different missense mutations: R249Q and R377L, in the EDMD2 and LGMD1B patient, respectively. The R249Q mutation is located within the central rod domain of the LMNA gene, and has been described in at least five unrelated sporadic EDMD2 patients. On the other hand, the R377L mutation, also located within the rod domain, is a novel mutation, although a histidine substitution instead of leucine (R377H) has been reported previously in an LGMD1B patient. To our knowledge, this is the first report of LMNA gene mutations in Korean patients with EDMD2 and LGMD1B.
Perrot A, etal., Basic Res Cardiol. 2009 Jan;104(1):90-9. doi: 10.1007/s00395-008-0748-6. Epub 2008 Sep 15.
The familial form of dilated cardiomyopathy (DCM) occurs in about 20%-50% of DCM cases. It is a heterogeneous genetic disease: mutations in more than 20 different genes have been shown to cause familial DCM. LMNA, encoding the nuclear membrane protein lamin A/
C, is one of the most important disease gene for that disease. Therefore, we analyzed the LMNA gene in a large cohort of 73 patients with familial DCM. Clinical examination (ECG, echocardiography, and catheterization) was followed by genetic characterization of LMNA by direct sequencing. We detected five heterozygous missense mutations (prevalence 7%) in five different families characterized by severe DCM and heart failure with conduction system disease necessitating pacemaker implantation and heart transplantation. Four of these variants clustered in the protein domain coil 1B, which is important for lamin B interaction and lamin A/C dimerization. Although we identified two novel mutations (E203V, K219T) besides three known ones (E161K, R190Q, R644C), it was remarkable that four mutations represent LMNA hot spots. DCM patients with LMNA mutations show a notable homogenous severe phenotype as we could confirm in our study. Testing LMNA in such families seems to be recommended because genotype information in an individual could definitely be useful for the clinician.
We have studied myoblasts from a patient with a severe autosomal dominant Emery-Dreifuss muscular dystrophy (AD-EDMD) caused by an arginine 545 to cystein point mutation (p.R545C) in the carboxy-terminal domain of the lamin A/C gene. This mutation has pleiotropic cellular effects on these myoblasts
as demonstrated by nuclear structural defects, exhibiting lobulations which increase with cell passages in culture. The organization of both lamin A/C and its inner nuclear membrane partner emerin are altered, eventually showing a honeycomb pattern upon immunofluorescence microscopy. In addition, the distribution of histone H3 trimethylated at lysine 27 and of phosphorylated RNA polymerase II, markers of inactive and active chromatin domains, respectively, are altered suggesting an impact on gene expression. Patient myoblasts also presented a high index of senescence in ex vivo culture. Moreover, our data show for the first time in an AD-EDMD context that the 20S core particle of the proteasome was inactivated. With cell passages, the 20S core protein progressively accumulated into discrete nuclear foci that largely colocalized with promyelocytic leukemia (PML) bodies while p21 accumulated throughout the nuclear compartment. Proteasome inactivation has been linked to normal cellular ageing. Our data indicate that it may also contribute to premature senescence in AD-EDMD patient myoblasts. Finally, when transferred to low-serum medium, patient myoblasts were deficient in ex vivo differentiation, as assessed by the absence of myotube formation and myogenin induction. Altogether, these data suggest that the LMNA mutation p.R545C impairs both proliferation and differentiation capacities of myoblasts as part of the pathogenesis of AD-EDMD.
Lu D, etal., PLoS One. 2010 Dec 6;5(12):e15167. doi: 10.1371/journal.pone.0015167.
The lamin A/C (LMNA), nuclear intermediate filament proteins, is a basic component of the nuclear lamina. Mutations in LMNA are associated with a broad range of laminopathies, congenital diseases affecting tissue regeneratio
n and homeostasis. Heart tissue specific transgenic mice of human LMNA E82K, a mutation causing dilated cardiomyopathy, were generated. Lmna(E82K) transgenic mouse lines exhibited thin-walled, dilated left and right ventricles, a progressive decrease of contractile function assessed by echocardiography. Abnormalities of the conduction system, myocytes disarray, collagen accumulation and increased levels of B-type natriuretic peptide (BNP), procollagen type III alpha1 (Col3alpha1) and skeletal muscle actin alpha1 (Actalpha1) were detected in the hearts of Lmna(E82K) transgenic mice. The LMNA E82K mutation caused mislocation of LMNA in the nucleus and swollen mitochondria with loss of critae, together with the loss of nuclear envelope integrity. Most interestingly, we found that the level of apoptosis was 8.5-fold higher in the Lmna(E82K) transgenic mice than that of non-transgenic (NTG) mice. In the presence of the LMNA E82K, both of FAS and mitochondrial pathways of apoptosis were activated consistent with the increase of FAS expression, the release of cytochrome c from mitochondria to cytosol and activation of caspase-8, -9 and -3. Our results suggested that the apoptosis, at least for the LMNA E82K or the mutations in the rod region of Lamin A/C, might be an important mechanism causing continuous loss of myocytes and lead to myocardial dysfunction. It could be a potential therapeutic means to suppress and/or prevent inappropriate cardiac cell death in patients carrying LMNA mutation.
Cao H and Hegele RA, J Hum Genet. 2003;48(5):271-4. Epub 2003 Apr 3.
Hutchinson-Gilford progeria syndrome (HGPS; MIM 176670) is an extremely rare disease that is characterized by accelerated aging and early death, frequently from coronary artery disease. Wiedemann-Rautenstrauch syndrome (WRS; MIM 264090) is another extremely rare disease that is characterized by pro
geroid features from birth with multiple somatic anomalies and paucity of subcutaneous fat. Because mutations in LMNA, encoding nuclear lamin A/C, cause other lipodystrophy syndromes, we sequenced LMNA (MIM 150330) from the genomic DNAs of seven unrelated HGPS probands and two unrelated WRS probands. We found four novel LMNA coding sequence variants among the HGPS probands, namely R471C, R527C, G608S and c.2036C>T. All seven HGPS probands had at least one LMNA variant, which were found in none of the genomes of 100 normal subjects ( P<4 x 10(-11)). In contrast, neither of the WRS proband genomes had any LMNA sequence abnormality. The strong association of rare LMNA coding sequence mutations with HGPS implicates this syndrome as a laminopathy, while WRS is most probably due to mutations in another gene.
BACKGROUND: Some LMNA mutations responsible for lipodystrophies, and some HIV-protease inhibitors (PIs) induce accumulation of farnesylated prelamin A and premature senescence in some cell types. Patients with LMNA mutation
s or under PI-based therapy suffer from early atherosclerosis. The metalloprotease ZMPSTE24 is the key enzyme in prelamin A maturation. AIM: We studied whether altered expression of ZMPSTE24 could contribute to vascular cell dysfunction in response to LMNA mutations or PI treatments. METHODS: Protein expression of prelamin A and ZMPSTE24 were evaluated in patients' cells and in human cultured VSMCs. Oxidative stress, inflammation, senescence and transdifferentiation/calcification were evaluated in VSMCs. RESULTS: Fibroblasts from LMNA-mutated lipodystrophic patients (mutations R482W, D47Y or R133L) and peripheral blood mononuclear cells from PI-treated-HIV-infected patients expressed increased prelamin A and decreased ZMPSTE24, which was also observed in VSMCs overexpressing mutant LMNA or treated with PIs. These alterations correlated with oxidative stress, inflammation, senescence and calcification (all p < 0.05). ZMPSTE24 silencing in native VSMCs recapitulated the mutant LMNA- and PI-induced accumulation of farnesylated prelamin A, oxidative stress, inflammation, senescence and calcification. A negative regulator of ZMPSTE24, miRNA-141-3p, was enhanced in LMNA-mutated or PI-treated VSMCs. The farnesylation inhibitors pravastatin and FTI-277, or the antioxidant N-acetyl cysteine, partly restored ZMPSTE24 expression, and concomitantly decreased oxidative stress, inflammation, senescence, and calcification of PI-treated VSCMs. CONCLUSIONS: ZMPSTE24 downregulation is a major contributor in VSMC dysfunctions resulting from LMNA mutations or PI treatments that could translate in early atherosclerosis at the clinical level. These novel pathophysiological mechanisms could open new therapeutic perspectives for cardiovascular aging.
BACKGROUND: Mutations in the LMNA gene, encoding lamins A/C, represent a significant cause of dilated cardiomyopathy. We recently identified 18 protein-altering LMNA variants in a cohort of 324 unrelated patients with dilate
d cardiomyopathy. However, at least one family member with dilated cardiomyopathy in each of 6 pedigrees lacked the LMNA mutation (nonsegregation), whereas small sizes of 5 additional families precluded definitive determinations of segregation, raising questions regarding contributions by those variants to disease. METHODS AND RESULTS: We have consequently expressed, in COS7 cells, GFP-prelamin A (GFPLaA) fusion constructs incorporating the 6 variants in pedigrees with nonsegregation (R101P, A318T, R388H, R399C, S437Hfsx1, and R654X), the 4 variants in pedigrees with unknown segregation (R89L, R166P [in 2 families], I210S, R471H), and 3 additional missense variants (R190Q, E203K, and L215P) that segregated with disease. Confocal immunofluorescence microscopy was used to characterize GFP-lamin A localization and nuclear morphology. Abnormal phenotypes were observed for 10 of 13 (77%) variants (R89L, R101P, R166P, R190Q, E203K, I210S, L215P, R388H, S437Hfsx1, and R654X), including 4 of 6 showing nonsegregation and 3 of 4 with uncertain segregation. All 7 variants affecting coil 1B and the lamin A-only mutation, R654X, exhibited membrane-bound GFP-lamin A aggregates and nuclear shape abnormalities. Unexpectedly, R388H largely restricted GFP-lamin A to the cytoplasm. Equally unexpected were unique streaked aggregates with S437Hfsx1 and giant aggregates with both S437Hfsx1 and R654X. CONCLUSIONS: This work expands the recognized spectrum of lamin A localization abnormalities in dilated cardiomyopathy. It also provides evidence supporting pathogenicity of 10 of 13 tested LMNA variants, including some with uncertain or nonsegregation.
Carboni N, etal., Muscle Nerve. 2010 Apr;41(4):458-63. doi: 10.1002/mus.21514.
Laminopathies are a heterogeneous group of LMNA-gene-mutation-related clinical disorders associated with alterations of cardiac and skeletal muscle and peripheral nerves, metabolic defects, and premature aging. Leg muscle imaging investigations were performed in
a cohort of patients with LMNA gene alterations who were suffering from Emery-Dreifuss muscular dystrophy, limb-girdle muscular dystrophy type 1B, isolated cardiac disorders or a phenotype of cardiac disorders, and lipodystrophy, including one individual with peripheral neuropathy. Leg muscle imaging revealed varying degrees of alteration in the soleus and medial head of gastrocnemius in each subject. This study demonstrates that LMNA-gene-mutated patients devoid of any clinically detectable skeletal muscle involvement have the same pattern of leg muscle involvement as patients with overt skeletal muscle compromise. This finding suggests the presence of a continuum of skeletal muscle involvement among phenotypes of LMNA-gene-mutation-related skeletalmyopathy and cardiomyopathy.
Carboni N, etal., Neuromuscul Disord. 2008 Apr;18(4):291-8. doi: 10.1016/j.nmd.2008.01.009. Epub 2008 Mar 11.
The case of a family in which several members displayed conduction defects inherited as a dominant trait is reported. The proband was a young woman with a 1st degree atrio-ventricular block and high serum creatine kinase. Several members of the family featured cardiologic symptoms. All adult family
members were clinically evaluated and blood tests including serum creatine-kinase levels, standard and Holter ECG, echocardiogram and muscle MRI were performed. LMNA gene analysis was carried out and a novel missense mutation consisting in substitution of exon 4 c.799 T/C, p.Tyr267His was revealed. The mutation was present in seven family members, five of whom displayed cardiac defects alone with no involvement of the skeletal muscle. In all mutated individuals muscle MRI featured a pattern of skeletal muscle involvement similar to that observed in autosomal dominant Emery Dreifuss muscular dystrophy, suggesting that even patients bearing a LMNA gene mutation associated to an apparently selective cardiac phenotype may present subclinical skeletal muscle involvement.
Rogozhina Y, etal., Gene. 2016 Dec 31;595(2):202-206. doi: 10.1016/j.gene.2016.10.001. Epub 2016 Oct 4.
BACKGROUND: Most of mutations in the LMNA gene are unique and have been found in only a few unrelated families. The clinical interpretation of new genetic variants, especially beyond the coding area and canonical splice sites, is proving to be difficult and req
uires advanced investigation. METHODS: This study included patients with progressive cardiac conduction defects with neuromuscular involvement. The clinical evaluation included medical history and 24-h Holter monitoring. The genetic evaluation included mutation screening in the LMNA gene by the Sanger sequence. Sanger sequencing was followed by RT-PCR of the target fragment of cDNA. In silico modeling was performed with CCBulder and Modeller software. RESULTS: The diagnosis of limb-girdle muscular dystrophy type 1B (LGMD1B) was established. The new intronic variant c.513+45T>G was found in the LMNA gene in the proband and affected daughter. The insertion of 45bp was confirmed in the proband's cDNA. The structural and possible functional effects of the aberrant protein were predicted. CONCLUSIONS: Variant c.513+45T>G in the LMNA gene likely translates into the longer lamin A/C proteins with additional 15 amino acids. This variant is thought to be pathogenic. Intronic variants in the LMNA gene located beside canonic splice sites may be responsible for some genotype-negative cases with clinical phenotype of laminopathies.
Decaudain A, etal., J Clin Endocrinol Metab. 2007 Dec;92(12):4835-44. Epub 2007 Aug 21.
CONTEXT: Mutations in the LMNA gene are responsible for several laminopathies, including lipodystrophies, with complex genotype/phenotype relationships. OBJECTIVE, DESIGN, SETTING, AND PATIENTS: Sequencing of the LMNA coding
regions in 277 unrelated adults investigated for lipodystrophy and/or insulin resistance revealed 17 patients with substitutions at codon 482 observed in typical Dunnigan's familial partial lipodystrophy and 10 patients with other mutations. We report here the phenotypes of the patients with non-codon 482 mutations and compare them with those of 11 patients with codon 482 mutations. We also studied skin fibroblasts or lymphocytes from seven patients. RESULTS: LMNA mutations found in nine patients studied here affected the three protein domains. Eight of them were novel. The 10 patients with non-codon 482-associated mutations fulfilled the International Diabetes Federation diagnosis criteria for metabolic syndrome. Most of them lacked the typical lipoatrophy observed in Dunnigan's familial partial lipodystrophy. However, the severity of insulin resistance, altered glucose tolerance, and hypertriglyceridemia and the alterations of cell nuclei were similar in patients with codon 482- and non-codon 482-associated mutations. Calf hypertrophy, myalgia, and muscle cramps or weakness were present in nine patients and cardiac conduction disturbances in two patients with non-codon 482 LMNA mutations. CONCLUSIONS: We describe here new phenotypes of metabolic laminopathy associated with non-codon 482 LMNA mutations and characterized, in the absence of obvious clinical lipoatrophy, by severe metabolic alterations and frequent muscle signs (muscular hypertrophy, myalgias, or weakness). Dual-energy x-ray absorptiometry and/or cross-sectional abdominal and thigh imaging can help diagnosis by revealing subclinical lipodystrophy. The prevalence and pathophysiology of metabolic laminopathies need to be studied further.
OBJECTIVE: The 3-bp deletion in exon 2 of the Lamin A/C (LMNA) gene has not been described in association with dilated cardiomyopathy, which is characterized by progressive heart failure, atrioventricular (AV) block, tachyarrhythmias, and variable skeletal musc
le involvement. CASE REPORT: In a 43-year-old woman with a long-term history of palpitations and newly diagnosed AV blocks I and II, ventricular ectopic beats, inducible nonsustained ventricular tachycardias (VTs), cardiac arrest, and successful resuscitation, an implantable cardioverter defibrillator was successfully implanted. Her family history was positive for sudden cardiac death (her father and sister), dyspnea and heart failure (her grandmother and sister), palpitations (her brother), and elevated levels of creatine-kinase (CK) (her sister). Two cousins had died of nonspecific muscular dystrophy at ages 10 years and 11 years. Upon neurological investigations revealing sore neck muscles, reduced tendon reflexes, and detached, spot-like white matter lesions bilaterally, a neuromuscular disorder was suspected. The direct sequencing of all exons and flanking intronic regions of the LMNA gene detected the heterozygote 3-bp deletion (AAG) c.367_369del in exon 2 of the gene. This mutation resulted in the deletion of a lysine at position 123 (p.lys123del) in the lamin A/C protein. CONCLUSIONS: The novel 3-bp deletion in exon 2 of the LMNA gene may phenotypically manifest as dilated cardiomyopathy, heart failure, severe tachyarrhythmias, and muscular dystrophy. Sudden cardiac death from ventricular fibrillation may be prevented in LMNA mutation carriers if the diagnosis is established early enough to implant a cardioverter defibrillator.
Nuclear lamin A and C alleles that are linked to three distinct human diseases have been expressed both in HeLa cells and in fibroblasts derived from Lmna null mice. Point mutations that cause dilated cardiomyopathy (L85R and N195K) and autosomal dominant Emery
-Dreifuss muscular dystrophy (L530P) modify the assembly properties of lamins A and C and cause partial mislocalization of emerin, an inner nuclear membrane protein, in HeLa cells. At the same time, these mutant lamins interfere with the targeting and assembly of endogenous lamins and in this way may cause significant changes in the molecular organization of the nuclear periphery. By contrast, lamin A and C molecules harboring a point mutation (R482W), which gives rise to a dominant form of familial partial lipodystrophy, behave in a manner that is indistinguishable from wild-type lamins A and C, at least with respect to targeting and assembly within the nuclear lamina. Taken together, these results suggest that nuclear structural defects could contribute to the etiology of both dilated cardiomyopathy and autosomal dominant Emery-Dreifuss muscular dystrophy.
The clinical course of a female patient affected by a progeroid syndrome with Restrictive Dermopathy (RD)-like features was followed up. Besides missing hairiness, stagnating weight and growth, RD-like features including progressive skin swelling and solidification, acrocontractures, osteolysis and
muscular hypotension were observed until the patient died at the age of 11 months. A homozygousLMNA mutation c.1303C>T (p.R435C) was found by Sanger sequencing. Haplotyping revealed a partial uniparental disomy of chromosome 1 (1q21.3 to 1q23.1) including the LMNA gene. In contrast to reported RD patients with LMNA mutations, LMNA p.R435C is not located at the cleavage site necessary for processing of prelamin A by ZMPSTE24 and leads to a distinct phenotype combining clinical features of Restrictive Dermopathy, Mandibuloacral Dysplasia and Hutchinson-Gilford Progeria. Functionally, LMNA p.R435C is associated with increasing DNA double strand breaks and decreased recruitment of P53 binding protein 1 (53BP1) to DNA-damage sites indicating delayed DNA repair. The follow-up of the complete clinical course in the patient combined with functional studies showed for the first time that a progressive loss of lamin A rather than abnormal accumulation of prelamin A species could be a pathophysiological mechanism in progeroid laminopathies, which leads to DNA repair deficiency accompanied by advancing tissue degeneration.
Madej-Pilarczyk A, etal., Am J Med Genet A. 2009 Nov;149A(11):2387-92. doi: 10.1002/ajmg.a.33018.
Hutchinson-Gilford progeria is a rare genetic disorder resulting from mutations in the LMNA gene encoding lamin A/C. In addition to the classical phenotype usually caused by the 1824C>T mutation of LMNA, a number of atypical
progeroid syndromes have been described. They have some distinct features, such as skeletal deformities or scleroderma-like skin changes. The underlying defect is usually a homozygous mutation of LMNA, or a combined defect of LMNA and another gene, for example, ZMPSTE-24. We present a 2-year-old girl born to consanguineous parents affected by progeroid syndrome with scleroderma-like skin changes. Genetic analysis revealed the homozygous LMNA mutation 1303C>T (R435C). The same heterozygous mutation was found in the patient's parents and 11 other family members. The progeroid syndrome in our patient shares the signs of two laminopathies: progeria and restrictive dermatopathy. Two other children in the family died at the age of 2 due to a disease similar to that in the proposita. On the basis of the family pedigree we presume that these children probably had the same homozygous LMNA mutation. Scleroderma-like skin changes in infants, associated with growth retardation and dysmorphic features, suggest premature aging syndrome, requiring genetic testing and counseling of asymptomatic carriers of LMNA mutations.
This study aimed to enhance understanding of LMNA mutation-related lipodystrophy by elucidating genotype-phenotype correlations and potential molecular mechanisms. Clinical data from six patients with LMNA mutation-related l
ipodystrophy are analyzed, and four distinct LMNA mutations are identified. Associations between mutations and lipodystrophy phenotypes are assessed. Three LMNA mutation plasmids are constructed and transfected into HEK293 cells. Protein stability, degradation pathways, and binding proteins of mutant Lamin A/C are examined using Western blotting, co-immunoprecipitation, and mass spectrometry. Confocal microscopy is employed to observe nuclear structure. Four different LMNA mutations are identified in the six patients, all exhibiting lipodystrophy and metabolic disorders. Cardiac dysfunction is observed in two out of six patients. Metformin and pioglitazone are the primary treatments for glucose control. Confocal microscopy revealed nuclear blebbing and irregular cell membranes. Mutant Lamin A/C stability is significantly decreased, and degradation occurred primarily via the ubiquitin-proteasome system (UPS). Potential binding ubiquitination-related proteins of mutant Lamin A/C are identified. This study investigated LMNA mutation-related lipodystrophy, identifying four unique mutations and their connections to specific phenotypes. It is found to decreased mutant Lamin A/C stability and degradation primarily through the UPS, offering new insights into molecular mechanisms and potential therapeutic targets.
Hirtle-Lewis M, etal., Clin Cardiol. 2013 Oct;36(10):628-33. doi: 10.1002/clc.22193. Epub 2013 Aug 27.
BACKGROUND: Dilated cardiomyopathy (DCM), which is characterized by left ventricular enlargement and systolic dysfunction, is divided into cases with a clear predisposing condition (eg, hypothyroidism, chemotherapeutic agents, alcoholism, ischemia) and those of unknown cause (idiopathic DCM). Many c
ases (20%-35%) of DCM are familial, implicating a genetic contribution to the etiology. More than 30 genes have been identified, many involving "private" mutations not shared among families. Evidence suggests that nonfamilial cases also have a genetic predisposition, again involving many genes. The goal of this study was to identify mutations in genes associated with DCM in a Quebec study sample including familial and nonfamilial DCM cases. HYPOTHESIS: A prioritized gene study conducted within a framework for the classification of identified genetic variants could yield etiological information even in the absence of family data. METHODS: We sequenced 4 previously identified genes: lamin A/C (LMNA), cardiac troponin T type 2 (TNNT2), titin-cap (TCAP), and phospholamban (PLN). RESULTS: We discovered a nonsense mutation in the LMNA gene and a frameshift mutation in the TNNT2 gene, as well as other clinically significant variants that were not observed in publicly available databases or in Quebec-based controls. PLN was sequenced to investigate a previously published promoter variant. However, our data confirm that this variant does not have a causal role in DCM. CONCLUSIONS: Despite high locus and allele heterogeneity, we demonstrate that a prioritized gene study, combined with next-generation exome-sequencing data, can be fruitful for the identification of DCM mutations.
Al-Saaidi R, etal., Exp Cell Res. 2013 Nov 15;319(19):3010-9. doi: 10.1016/j.yexcr.2013.08.024. Epub 2013 Aug 31.
Dilated cardiomyopathy (DCM) is a disease of the heart muscle characterized by cardiac chamber enlargement and reduced systolic function of the left ventricle. Mutations in the LMNA gene represent the most frequent known genetic cause of DCM associated with dis
ease of the conduction systems. The LMNA gene generates two major transcripts encoding the nuclear lamina major components lamin A and lamin C by alternative splicing. Both haploinsuffiency and dominant negative effects have been proposed as disease mechanism for premature termination codon (PTC) mutations in LMNA. These mechanisms however are still not clearly established. In this study, we used a representative LMNA nonsense mutation, p.Arg321Ter, to shed light on the molecular disease mechanisms. Cultured fibroblasts from three DCM patients carrying this mutation were analyzed. Quantitative reverse transcriptase PCR and sequencing of these PCR products indicated that transcripts from the mutant allele were degraded by the nonsense-mediated mRNA decay (NMD) mechanism. The fact that no truncated mutant protein was detectable in western blot (WB) analysis strengthens the notion that the mutant transcript is efficiently degraded. Furthermore, WB analysis showed that the expression of lamin C protein was reduced by the expected approximately 50%. Clearly decreased lamin A and lamin C levels were also observed by immunofluorescence microscopy analysis. However, results from both WB and nano-liquid chromatography/mass spectrometry demonstrated that the levels of lamin A protein were more reduced suggesting an effect on expression of lamin A from the wild type allele. PCR analysis of the ratio of lamin A to lamin C transcripts showed unchanged relative amounts of lamin A transcript suggesting that the effect on the wild type allele was operative at the protein level. Immunofluorescence microscopy analysis showed no abnormal nuclear morphology of patient fibroblast cells. Based on these data, we propose that heterozygosity for the nonsense mutation causes NMD degradation of the mutant transcripts blocking expression of the truncated mutant protein and an additional trans effect on lamin A protein levels expressed from the wild type allele. We discuss the possibility that skewing of the lamin A to lamin C ratio may contribute to ensuing processes that destabilize cardiomyocytes and trigger cardiomyopathy.
Wojtanik KM, etal., J Lipid Res. 2009 Jun;50(6):1068-79. doi: 10.1194/jlr.M800491-JLR200. Epub 2009 Feb 5.
We investigated the role of LMNA in adipose tissue by developing a novel mouse model of lipodystrophy. Transgenic mice were generated that express the LMNA mutation that causes familial partial lipodystrophy of the Dunnigan
type (FPLD2). The phenotype observed in FPLD-transgenic mice resembles many of the features of human FPLD2, including lack of fat accumulation, insulin resistance, and enlarged, fatty liver. Similar to the human disease, FPLD-transgenic mice appear to develop normally, but after several weeks they are unable to accumulate fat to the same extent as their wild-type littermates. One poorly understood aspect of lipodystrophies is the mechanism of fat loss. To this end, we have examined the effects of the FPLD2 mutation on fat cell function. Contrary to the current literature, which suggests FPLD2 results in a loss of fat, we found that the key mechanism contributing to the lack of fat accumulation involves not a loss, but an apparent inability of the adipose tissue to renew itself. Specifically, preadipocytes are unable to differentiate into mature and fully functional adipocytes. These findings provide insights not only for the treatment of lipodystrophies, but also for the study of adipogenesis, obesity, and insulin resistance.
