Heterozygous mutation or deletion of Pafab1b1 (LIS1) in humans is associated with syndromes with type 1 lissencephaly, a severe brain developmental disorder resulting from abnormal neuronal migration. We have created Lis1 heterozygous mutant mice by gene targeting. Heterozygous mutant mice are viabl
e and fertile, but display global organizational brain defects as a result of impaired neuronal migration. To assess the functional impact of the mutation, Lis1 heterozygous mice and their wild-type littermates were evaluated on a wide variety of behavioral tests. Lis1 mutant mice displayed abnormal hindpaw clutching responses and were impaired on a rotarod test. Lis1 heterozygous mice were also impaired in the spatial learning version of the Morris water task. Impaired motor behavior and spatial learning and memory in Lis1 mutant mice indicates that impaired neuronal migration can have functional effects on complex behavioral responses. The behavioral findings also support the use of the Lis1 mutant mice as a model from human type 1 lissencephaly.
Yao GD, etal., Reprod Biomed Online. 2015 Nov;31(5):613-24. doi: 10.1016/j.rbmo.2015.07.010. Epub 2015 Aug 7.
Spermatogenesis, fertilization and subsequent embryonic development are complex processes that require tight regulation. The PAFAH1B1 gene plays important roles in these reproductive events in mice, but its expression and roles in human reproduction have not be
en investigated. Expression analysis of testicular tissue by reverse transcription quantitative PCR and immunohistochemistry revealed varied expression levels among samples of different spermatogenic abilities (as assessed by the Johnsen score), with protein expression restricted to spermatogonia, spermatocytes and spermatids. Immunofluorescence on spermatozoa showed expression over the acrosome and midpiece regions of ejaculated samples, whereas a high proportion of percutaneous epididymal sperm aspiration-derived spermatozoa showed expression restricted to the midpiece. Analysis for PAFAH1B1 mRNA also revealed different expression levels among unfertilized oocytes, zygotes, cleavage stage embryos and blastocysts, with protein localized at the membrane level in oocytes and zygotes, and gradually distributing within the cytoplasm of cleavage stage embryos and blastocysts. Interestingly, microinjection of PAFAH1B1 siRNA into zygotes significantly (P = 0.024) increased fragmentation formation rates in subsequent embryonic development stages. Altogether, these are the first results to support a role for PAFAH1B1 in human spermatogenesis and early embryonic development.
Classical lissencephaly (LIS) and subcortical band heterotopia (SBH) are related cortical malformations secondary to abnormal migration of neurons during early brain development. Approximately 60% of patients with classical LIS, and one patient with atypical SBH have been found to have deletions or
mutations of the LIS1 gene, located on 17p13.3. This gene encodes the LIS1 or PAFAH1B1 protein with a coiled-coil domain at the N-terminus and seven WD40 repeats at the C-terminus. It is highly conserved between species and has been shown to interact with multiple proteins involved with cytoskeletal dynamics, playing a role in both cellular division and motility, as well as the regulation of brain levels of platelet activating factor. Here we report 65 large deletions of the LIS1 gene detected by FISH and 41 intragenic mutations, including four not previously reported, the majority of which have been found as a consequence of the investigation of 220 children with LIS or SBH by our group. All intragenic mutations are de novo, and there have been no familial recurrences. Eight-eight percent (36/41) of the mutations result in a truncated or internally deleted protein-with missense mutations found in only 12% (5/41) thus far. Mutations occurred throughout the gene except for exon 7, with clustering of three of the five missense mutations in exon 6. Only five intragenic mutations were recurrent. In general, the most severe LIS phenotype was seen in patients with large deletions of 17p13.3, with milder phenotypes seen with intragenic mutations. Of these, the mildest phenotypes were seen in patients with missense mutations.
