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Expression of deoxyribonucleic acid repair enzymes during spermatogenesis in mice
L L Richardson1, C Pedigo, M Ann Handel
1Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996-0840, USA. lrichar5@utk.edu
Abstract:
Meiotic recombination during gametogenesis is critical for proper chromosome segregation. However, the participating proteins and mechanics of recombination are not well understood in mammals. DNA repair enzymes play an essential role in both mitosis and meiosis in yeast. The mammalian mismatch repair system consists of homologues of the bacterial MutH, MutL, and MutS proteins. As part of our goal of understanding the function of enzymes that mediate meiotic recombination, we used a reverse transcription-polymerase chain reaction approach to identify germ cell transcripts for the MutL homologue, Pms2, and two members of the MutS family, Msh2 and Msh3. Both the Pms2 and the Msh2 genes were highly expressed in mitotically proliferating spermatogonia, and early in meiotic prophase in the leptotene and zygotene spermatocytes. Thereafter, expression declined in early and mid pachytene spermatocytes, and was negligible in postmeiotic spermatids. In contrast, expression of Msh3 was at its highest level in pachytene spermatocytes. Protein levels were similar to gene expression patterns, and both PMS2 and MSH2 were localized in spermatogonia and spermatocytes. These patterns of expression for genes encoding mismatch repair enzymes are consistent with the proposed roles of the gene products in mismatch repair during both DNA replication and recombination.
Insights
Mammalian mismatch repair enzymes Pms2 and Msh2 are crucial for meiosis, with expression peaking during early stages of sperm development. Msh3 expression is highest in later meiotic stages, suggesting distinct roles in recombination.
Area of Science:
- Genetics
- Molecular Biology
- Reproductive Biology
Background:
- Meiotic recombination is essential for accurate chromosome segregation during gametogenesis.
- The specific proteins and mechanisms of mammalian meiotic recombination remain incompletely understood.
- DNA repair enzymes are known to be vital for both mitosis and meiosis in yeast.
Purpose of the Study:
- To investigate the expression patterns of key mismatch repair (MMR) genes in mammalian germ cells.
- To understand the potential roles of MMR enzymes in meiotic recombination and DNA repair during spermatogenesis.
Main Methods:
- Utilized reverse transcription-polymerase chain reaction (RT-PCR) to detect germ cell transcripts for Pms2, Msh2, and Msh3.
- Analyzed gene expression levels across different stages of spermatogenesis (spermatogonia, spermatocytes, spermatids).
- Examined protein localization using immunofluorescence in germ cells.
Main Results:
- Pms2 and Msh2 genes showed high expression in proliferating spermatogonia and early meiotic prophase (leptotene, zygotene spermatocytes).
- Expression of Pms2 and Msh2 decreased in later meiotic stages (pachytene) and was minimal in spermatids.
- Msh3 expression was highest in pachytene spermatocytes, contrasting with Pms2 and Msh2 patterns.
- PMS2 and MSH2 proteins were localized in spermatogonia and spermatocytes, correlating with gene expression.
Conclusions:
- The observed expression patterns of Pms2, Msh2, and Msh3 support their involvement in DNA mismatch repair during mammalian gametogenesis.
- These findings suggest distinct temporal roles for MMR enzymes in DNA replication and recombination processes during meiosis.