Role Of Cohesins In Drosophila Male Meiosis. Avik Mukherjee¹, Bruce McKee^1,2. 1) Genome Science and Technology, University of Tennessee, Knoxville, TN; 2) Department of Biochemistry Cell and Molecular Biology, University of Tennessee, Knoxville, TN.

   Meiosis is driven by the pairing and proper segregation of both sister chromatids and homologous chromosomes. Cohesion between sister chromatids plays multiple roles in pairing and segregation of homologs as well as sister chromatids. It depends, in both mitosis and meiosis, on a conserved protein complex, cohesin, that forms a ring around duplicated sister chromatids and prevents them from separating prematurely. Insight into the structure and role of cohesin in Drosophila meiosis is thus far very limited. The Drosophila genome encodes single orthologs of SMC1 and SMC3 and two orthologs of RAD21 (RAD21 and C(2)M) and SCC3/SA (SA and SNM) cohesin proteins. Previous work has shown that in Drosophila male meiosis pairing depends on two chromosomal proteins (Stromalin in meiosis (SNM) and Mod(Mdg4) in Meiosis (MNM)) that stably maintain homolog pairing throughout meiosis I. SNM is a paralog of one of the core cohesin genes SA/SCC3, raising the possibility of a central role of cohesin in homolog pairing. Mutations in c(2)m are meiosis specific and are related to synapsis in female meiosis but is not essential for sister chromatid cohesion. The protein Ord is required for centromeric cohesion and colocalizes with SMC1 protein at the centromeres of meiotic chromosomes. Another gene, solo, is required for both homolog and sister chromatid segregation in both sexes and colocalizes on chromosomes with cohesin proteins. We are investigating the role of cohesin in Drosophila male meiosis by using germ-line specific RNAi against the genes encoding the core cohesin proteins SMC1 and SMC3 which are long coiled-coil proteins that, together with SCC1/RAD21, are thought to form a tripartite ring that topologically constrains sister chromatid pairs.The effect of cohesin mutation on meiotic pairing and cohesion will be presented.