This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Human infertility and complications of reproductive processes have devastating social and monetary costs. We are attempting to identify genes necessary for fertility by studying mammalian meiosis using gene knock-outs, expression profiling, and immunohistochemistry in the mouse, as a model system. For meiosis to succeed a complicated series of processes must occur including cell cycle progression, recombination, chromosome segregation and cell division. Phenotype-driven mutagenic screens have generated the mutation mei4. mei4 causes male and female sterility by disrupting gametogenesis during meiosis. Meiosis in mei4/mei4 homozygotes fails to complete due to a lack of recombination. While other DNA repair proteins such as Rad51 localize normally to meiotic chromosomes, the mismatch repair protein Mlh1 fails to load onto meiotic chromosomes during the pachytene to diplotene transition in mei4/mei4 animals. We have identified what we believe to be the causative mutation behind the mei4 phenotype in a putative E3 ligase functions to regulate cyclin degredation. This application proposes to unambiguously identify and characterize the mutant mei4 allele in the context of meiotic DNA repair and cell cycle biology. The role of mei4 in DNA mismatch repair and cell cycle progression will be elucidated via the following specific aims and strategies:(1) gene knock-out and complementation of the mei4 allele, (2) immunohistochemistry of protein constituents at recombination sites, (3) mRNA and protein expression profiling, and in vitro interaction studies. This work has significant health relatedness as several of the mismatch repair proteins found to function in meiosis are also associated with hereditary non-polyposis colorectal cancer (HNPCC). E3 ligases and their substrates have been implicated in several cancers, including inherited breast cancer, and also in neurodegenerative disorders. Lastly, a major source of birth defects is aneuploidy resulting from non-disjunction or premature separation of meiotic chromosomes. mei4 has a severe meiotic aneuploid phenotype and thus its identification and characterization will address potential causes of clinical aneuploidy and birth defects. The characterization of mei4 will not only contribute to our understanding of the basic molecular biology of meiosis but also increase our knowledge of important human health issues.
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