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Author Spotlight: Understanding DNA Damage Response in Mammalian Oocytes and Preimplantation Embryos
Published on: June 23, 2023
The DNA double-strand break repair proteins γH2AX, RAD51, BRCA1, RPA70, KU80, and XRCC4 exhibit follicle-specific
Gunel Talibova1, Yesim Bilmez1, Betul Tire1
1Department of Histology and Embryology, Akdeniz University School of Medicine, Campus, 07070, Antalya, Turkey.
Purpose:
Ovarian aging is closely related to a decrease in follicular reserve and oocyte quality. The precise molecular mechanisms underlying these reductions have yet to be fully elucidated. Herein, we examine spatiotemporal distribution of key proteins responsible for DNA double-strand break (DSB) repair in ovaries from early to older ages. 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.
Methods:
Female Balb/C mice were divided into five groups as follows: Prepuberty (3 weeks old; n = 6), puberty (7 weeks old; n = 7), postpuberty (18 weeks old; n = 7), early aged (52 weeks old; n = 7), and late aged (60 weeks old; n = 7). The expression of DSB repair proteins, cellular senescence (β-GAL) and apoptosis (cCASP3) markers was evaluated in the ovaries using immunohistochemistry.
Result:
β-GAL and cCASP3 levels progressively increased from prepuberty to aged groups (P < 0.05). Notably, γH2AX levels varied in preantral and antral follicles among the groups (P < 0.05). In aged groups, RAD51, BRCA1, KU80, and XRCC4 levels increased (P < 0.05), while RPA70 levels decreased (P < 0.05) compared to the other groups.
Conclusions:
The observed alterations were primarily attributed to altered expression in oocytes and granulosa cells of the follicles and other ovarian cells. As a result, the findings indicate that these DSB repair proteins may play a role in the repair processes and even other related cellular events in ovarian cells from early to older ages.
Insights
Ovarian aging involves changes in DNA double-strand break (DSB) repair proteins. Aged ovaries show increased RAD51, BRCA1, KU80, and XRCC4, and decreased RPA70, impacting oocyte and follicle health.
Area of Science:
- Reproductive biology and molecular genetics.
- Cellular and molecular mechanisms of aging.
Background:
- Ovarian aging is characterized by reduced follicular reserve and oocyte quality.
- The molecular underpinnings of ovarian aging, particularly DNA repair processes, require further elucidation.
Purpose of the Study:
- To investigate the spatiotemporal distribution of key DNA double-strand break (DSB) repair proteins in mouse ovaries across different age groups.
- To understand the roles of homologous recombination (HR) and classical non-homologous end joining (cNHEJ) pathway proteins in ovarian aging.
Main Methods:
- Female Balb/C mice were categorized into five age groups: prepuberty, puberty, postpuberty, early aged, and late aged.
- Immunohistochemistry was employed to evaluate the expression of DSB repair proteins (γH2AX, RAD51, BRCA1, RPA70, KU80, XRCC4), cellular senescence (β-GAL), and apoptosis (cCASP3) markers in ovarian tissues.
Main Results:
- Cellular senescence and apoptosis markers (β-GAL, cCASP3) significantly increased with age.
- γH2AX levels showed variations in preantral and antral follicles across age groups.
- Aged ovaries exhibited elevated levels of RAD51, BRCA1, KU80, and XRCC4, alongside decreased RPA70 levels, particularly in oocytes and granulosa cells.
Conclusions:
- Age-related changes in DSB repair protein expression occur in ovarian cells, including oocytes and granulosa cells.
- These alterations in DNA repair proteins may contribute to cellular events associated with ovarian aging.
- The findings suggest a potential role for DSB repair pathways in maintaining ovarian function throughout reproductive lifespan.
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