PARENT SESSION
GAMETE BIOLOGY AND GAMETOGENESIS - C

Wednesday, August 4, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(698) IMPLICATIONS OF SPERM DNA DAMAGE IN EXPRESSION OF RAD51 AND P53 IN ZYGOTES AND TWO-CELL EMBRYOS SIRED BY GOLDEN HAMSTERS WITH MAJOR ACCESSORY SEX GLANDS REMOVED.

Chen, Hong¹, Cheung, May PL¹, Chow, PH², Cheung, Annie LM¹, O, Wai Sum¹, ¹ The University of Hong Kong, Hong Kong, P. R. of China² The Chinese University of Hong Kong, Hong Kong, P. R. of China

ABSTRACT- Previous reports showed that removal of all or some male accessory sex glands (ASGs) in the golden hamster could reduce male fertility because of increased embryo wastage. Male ASGs being the main source of antioxidants has been shown to protect sperm genomic integrity and functional competence. In this study, single cell gel electrophoresis or comet assay was used to assess single-stranded (ss) and double-stranded (ds) DNA damage in zygotes at 5 hours post coitum (p.c.) and 2-cell embryos at 22 hours p.c. sired by hamsters with all ASGs removed (TX) or sham-operated males (SH). Immunocytochemistry was applied to colocalize the DNA repair enzyme, RAD51, and the tumour suppressor factor, p53, in zygotes and 2-cell embryos. While all female pronuclei in zygotes sired by both groups of males were intact, 7.0% of ssDNA damage and 5.1% of dsDNA damage were found in decondensed sperm nuclei in the TX group only (P<0.05, compared with SH control, Fisher′s exact test). 5.0% of DNA damage could be detected in both nuclei of the 2-cell embryos sired by TX hamsters (P<0.05, compared with SH control, Fisher′s exact test). RAD51 was found to be evenly distributed in the cytoplasm and nuclei of unfertilized oocytes and zygotes. In the 2-cell embryos, RAD51 signals were attenuated in the perinuclear area in both SH and TX groups. The larger clear area around both nuclei seen in the TX embryos was accompanied by a strong expression of p53 protein in the nuclei of the blastomeres. In conclusion, this study gave direct evidence for the first time that DNA damage could be found in decondensed sperm in zygotes and in both blastomeres of 2-cell stage embryos sired by hamsters with all ASGs removed, and that a reduction of RAD51 protein and stronger expression of p53 protein detected in 2-cell embryos may imply activation of DNA repair mechanisms.

KEY WORDS: DNA damage, Accessory sex glands of hamster, RAD51, p53, zygote, 2-cell embryo