Van Camp G, etal., Am J Hum Genet. 2006 Sep;79(3):449-57. doi: 10.1086/506478. Epub 2006 Jun 26.
Stickler syndrome is characterized by ophthalmic, articular, orofacial, and auditory manifestations. It has an autosomal dominant inheritance pattern and is caused by mutations in COL2A1, COL11A1, and COL11A2. We describe a family of Moroccan origin that consists of four children with Stickler syndr
ome, six unaffected children, and two unaffected parents who are distant relatives (fifth degree). All family members were clinically investigated for ear, nose, and throat; ophthalmologic; and radiological abnormalities. Four children showed symptoms characteristic of Stickler syndrome, including moderate-to-severe sensorineural hearing loss, moderate-to-high myopia with vitreoretinopathy, and epiphyseal dysplasia. We considered the COL9A1 gene, located on chromosome 6q13, to be a candidate gene on the basis of the structural association with collagen types II and XI and because of the high expression in the human inner ear indicated by cDNA microarray. Mutation analysis of the coding region of the COL9A1 gene showed a homozygous R295X mutation in the four affected children. The parents and four unaffected children were heterozygous carriers of the R295X mutation. Two unaffected children were homozygous for the wild-type allele. None of the family members except the homozygous R295X carriers had any signs of Stickler syndrome. Therefore, COL9A1 is the fourth identified gene that can cause Stickler syndrome. In contrast to the three previously reported Stickler syndrome-causing genes, this gene causes a form of Stickler syndrome with an autosomal recessive inheritance pattern. This finding will have a major impact on the genetic counseling of patients with Stickler syndrome and on the understanding of the pathophysiology of collagens. Mutation analysis of this gene is recommended in patients with Stickler syndrome with possible autosomal recessive inheritance.
PURPOSE: To investigate COL9A1 in two families suggestive of autosomal recessive Stickler syndrome and to delineate the associated phenotype. METHODS: The probands of two consanguineous autosomal recessive Stickler families were evaluated fo
r homozygosity using SNP microarray in one and haplotype analysis in the other. Subsequently, the entire COL9A1 open reading frame was analyzed by DNA sequencing in all members of the respective families. Several family members were investigated for dysmorphic features as well as ophthalmic, audiologic, and radiologic abnormalities. RESULTS: A novel homozygous COL9A1 mutation (p.R507X) was identified in two affected Turkish sisters, and the previously published mutation (p.R295X) was found in a Moroccan boy. Ophthalmic assessment revealed myopia, cataracts, distinct vitreous changes, progressive chorioretinal degeneration, and exudative and rhegmatogenous retinal detachments. All three had sensorineural hearing loss and epiphyseal dysplasia. Intervertebral disc bulging was observed in one patient and in two heterozygous carriers of the p.R507X mutation. CONCLUSIONS: A second, novel mutation was identified in COL9A1, causing autosomal recessive Stickler syndrome together with the previously described nucleotide change in two separate families. Although the overall phenotype was comparable to autosomal dominant Stickler, vitreous changes that may enable recognition of patients who are likely to carry mutations in COL9A1 were identified, and exudative retinal detachment was observed as a new finding in Stickler syndrome.
Czarny-Ratajczak M, etal., Am J Hum Genet. 2001 Nov;69(5):969-80. Epub 2001 Sep 14.
Multiple epiphyseal dysplasia (MED) is an autosomal dominantly inherited chondrodysplasia. It is clinically highly heterogeneous, partially because of its complex genetic background. Mutations in four genes, COL9A2, COL9A3, COMP, and MATR3, all coding for cartilage extracellular matrix components (i
.e., the alpha2 and alpha 3 chains of collagen IX, cartilage oligomeric matrix protein, and matrilin-3), have been identified in this disease so far, but no mutations have yet been reported in the third collagen IX gene, COL9A1, which codes for the alpha1(IX) chain. MED with apparently recessive inheritance has been reported in some families. A homozygous R279W mutation was recently found in the diastrophic dysplasia sulfate transporter gene, DTDST, in a patient with MED who had a club foot and double-layered patella. The series consisted of 41 probands with MED, 16 of whom were familial and on 4 of whom linkage analyses were performed. Recombination was observed between COL9A1, COL9A2, COL9A3, and COMP and the MED phenotype in two of the families, and between COL9A2, COL9A3, and COMP and the phenotype in the other two families. Screening of COL9A1 for mutations in the two probands from the families in which this gene was not involved in the recombinations failed to identify any disease-causing mutations. The remaining 37 probands were screened for mutations in all three collagen IX genes and in the COMP gene. The probands with talipes deformities or multipartite patella were also screened for the R279W mutation in DTDST. The analysis resulted in identification of three mutations in COMP and one in COL9A1, but none in the other two collagen IX genes. Two of the probands with a multipartite patella had the homozygous DTDST mutation. The results show that mutations in COL9A1 can cause MED, but they also suggest that mutations in COL9A1, COL9A2, COL9A3, COMP, and DTDST are not the major causes of MED and that there exists at least one additional locus.
Mustafa Z, etal., Rheumatology (Oxford) 2000 Mar;39(3):299-306.
OBJECTIVE: To examine 11 candidate genes as susceptibility loci for osteoarthritis (OA). METHODS: A total of 481 families have been ascertained in which at least two siblings have had joint replacement surgery of the hip, or knee, or hip and knee for idiopathic OA. Each candidate gene was targeted u
sing one or more intragenic or closely linked microsatellite marker. The linkage data were analysed unstratified and following stratification by sex and by joint replaced (hip or knee). RESULTS: The analyses revealed suggestive linkage of the type IX collagen gene COL9A1 (6q12-q13) to a subset of 132 families that contained affected females who were concordant for hip OA (female-hip) with a P-value of 0.00053 and logarithm of the odds (LOD) score of 2.33 [corrected P-value of 0. 0016, corrected LOD score of 1.85]. CONCLUSIONS:COL9A1 may therefore be a susceptibility locus for female hip OA. In addition, there was weak evidence of linkage to HLA/COL11A2 (6p21.3) in female hip OA with a corrected P-value of 0.016.
Usami S, etal., Neuroscience. 2008 Jun 12;154(1):22-8. doi: 10.1016/j.neuroscience.2008.03.018. Epub 2008 Mar 19.
Genes that are highly expressed in the inner ear, as revealed by cDNA microarray analysis, may have a crucial functional role there. Those that are expressed specifically in auditory tissues are likely to be good candidates to screen for genetic alterations in patients with deafness, and several ge
nes have been successfully identified as responsible for hereditary hearing loss. To understand the detailed mechanisms of the hearing loss caused by the mutations in these genes, the present study examined the immunocytochemical localization of the proteins encoded by Crym, KIAA1199 homolog, Uba52, Col9a3, and Col9a1 in the cochlea of rats and mice. Confocal microscopic immunocytochemistry was performed on cryostat sections. Ultrastructurally, postembedding immunogold cytochemistry was applied using Lowicryl sections. Crym protein was predominantly distributed in the fibrocytes in the spiral ligament, as well as the stria vascularis in rats. KIAA1199 protein homolog was localized in various supporting cells, including inner phalangeal, border, inner and outer pillar, and Deiters' cells. Uba52 protein was restrictedly localized within the surface of the marginal cells of the stria vascularis. Collagen type IX was found within the tectorial membrane as well as fibrocytes in the spiral ligament. The present results showed cell-specific localization of the encoded proteins of these highly expressed genes, indicating that the coordinated actions of various molecules distributed in different parts of the cochlea are essential for maintenance of auditory processing in the cochlea.
