Expression of deoxyribonucleic acid repair enzymes during spermatogenesis in mice

Meiotic recombination during gametogenesis is critical for proper chromosom e segregation. However, the participating proteins and mechanics of recombi nation are not well understood in mammals, DNA repair enzymes play an essen tial role in both mitosis and meiosis in yeast. The mammalian mismatch repa ir system consists of homologues of the bacterial MutH, MutL, and MutS prot eins. As part of our goal of understanding the function of enzymes that med iate meiotic recombination, we used a reverse transcription-polymerase chai n reaction approach to identify germ cell transcripts for the MutL homologu e, Pms2, and two members of the MutS family, Msh2 and Msh3. Both the Pms2 a nd the Msh2 genes were highly expressed in mitotically proliferating sperma togonia, and early in meiotic prophase in the leptotene and zygotene sperma tocytes. Thereafter, expression declined in early and mid pachytene spermat ocytes, and was negligible in postmeiotic spermatids. In contrast, expressi on of Msh3 was at its highest level in pachytene spermatocytes. Protein lev els were similar to gene expression patterns, and both PMS2 and MSH2 were l ocalized in spermatogonia and spermatocytes. These patterns of expression f or genes encoding mismatch repair enzymes are consistent with the proposed roles of the gene products in mismatch repair during both DNA replication a nd recombination.