Submission Number: MAR-4-19-5

Abstract Number: 579

DNA DAMAGE DELAYS INDUCED MEIOTIC G2/M TRANSITION IN MOUSE SPERMATOCYTES.

MA Handel, DK Andreadis and J Cobb

Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, USA ¹

Abstract:
DNA damage is known to activate checkpoints that delay entry into mitotic division phase, although comparatively little is known about such checkpoints in meiotic cells. In order to test for checkpoints operable in meiosis, DNA damage was induced in cultured prophase mouse spermatocytes. Cells were observed to determine any possible abnormalities in the chromosome condensation events of their first G2/M transition. DNA damage was induced by three methods: X-irradiation, treatment with the radiomimetic drug bleomycin (BLM) or treatment with teniposide, a topoisomerase II inhibitor that leaves unligated double-strand breaks in DNA. Similarities of results among the three agents with respect to both cell-cycle delay and accumulation of RAD51 foci suggests that cellular responses were due to induced DNA damage and not dependent on which specific agent caused the DNA strand breaks. Induction of DNA damage in pachytene spermatocytes resulted in a dose-dependent increase in number of foci of RAD51, a protein that accumulates at sites of DNA double-strand breaks. DNA damage inhibited condensation of chiasmate bivalent chromosomes in response to okadaic acid, a phosphatase inhibitor that can induce precocious onset of meiotic metaphase. The inhibition of G2/M transition caused by BLM was partially reversible when BLM was removed from the culture medium. This reversal suggests that pachytene spermatocytes have an active DNA-damage repair process that may be monitored by checkpoints. (Supported by a grant from the NIH, HD33816, to MAH).

Keywords: meiosis, spermatogenesis, DNA damage, cell cycle

This abstract is being presented at: 8:00 AM in session:
Spermatogenesis