The DNA double-strand break repair proteins γH2AX, RAD51, BRCA1, RPA70, KU80, and XRCC4 show follicle-specific expression differences in the postnatal mouse ovaries from early to older ages

Abstract

Abstract Ovarian aging is closely related to a decrease in follicular reserve and oocyte quality. The underlying molecular causes of these changes have not been fully explored. Herein, we examine spatiotemporal distribution of key proteins responsible for DNA double-strand break (DSB) repair from early to older ovaries. Functional studies have shown that the γH2AX, RAD51, BRCA1, and RPA70 proteins play indispensable roles in HR-based repair pathway, while the KU80 and XRCC4 proteins are essential for successfully operating cNHEJ pathway. As expected, β-GAL levels increased progressively from prepuberty to aged groups (P < 0.05). Interestingly, we observed significant changes in γH2AX levels of the preantral and antral follicles (P < 0.05), and cCASP3 levels increased in the aged groups (P < 0.05). While RAD51, BRCA1, KU80, and XRCC4 protein levels increased (P < 0.05), the protein level of RPA70 decreased in the aged groups (P < 0.05) compared to the remaining groups. These changes mainly resulted from altered expression in oocytes and granulosa cells of the follicles and other ovarian cells. All these results suggest that DSBs in ovarian cells during aging are rapidly repaired by activating the HR and cNHEJ pathways. Meanwhile, unrepaired ovarian cells seem to be removed through apoptosis or undergo cellular senescence.