Aging alters histone H4 acetylation and CDC2A in mouse germinal vesicle stage oocytes

Area of Science:

• Reproductive Biology
• Epigenetics
• Cellular Aging

Background:

• Mammalian reproductive potential declines with age, leading to infertility.
• Aging affects gene expression, histone acetylation, and protein function in metaphase II (MII) oocytes.
• MII oocytes develop from germinal vesicle (GV)-stage oocytes.

Purpose of the Study:

• To investigate if aging-related defects in MII oocytes originate at the GV stage.
• To examine the impact of aging on histone H4 acetylation at specific lysines (H4K5, H4K8, H4K12, H4K16) in GV and MII oocytes.
• To assess the relationship between histone acetylation and Cdc2a expression and activity in aging oocytes.

Main Methods:

• Analysis of histone H4 acetylation patterns (H4K5, H4K8, H4K12, H4K16) in young and old GV and MII oocytes.
• Quantification of Cdc2a gene expression in different oocyte stages.
• Measurement of CDC2A protein levels and kinase activity.
• Intervention to correct histone deacetylation at the GV stage and assess downstream effects on MII oocytes.

Main Results:

• Acetylation of H4K12 and H4K16 was reduced in old GV oocytes.
• H4K12 acetylation increased in old MII oocytes, while Cdc2a expression varied (increased in nonsurrounded nucleolus, decreased in MII).
• CDC2A protein and kinase activity declined in both old GV and MII oocytes.
• Restoring GV stage histone deacetylation normalized H4K12 acetylation and CDC2A protein in MII oocytes.

Conclusions:

• Abnormalities in histone acetylation at the GV stage are a primary cause of age-related MII oocyte dysfunction.
• Targeting the GV stage offers a potential strategy to mitigate aging-induced infertility.
• Epigenetic modifications during early oocyte development are critical for maintaining reproductive competence throughout aging.