The prophase oocyte nucleus is a homeostatic G-actin buffer.

Area of Science:

• Cell Biology
• Reproductive Biology
• Developmental Biology

Background:

• Healthy mammalian egg formation depends on specialized actin filament (F-actin) structures.
• Disruption of F-actin leads to aneuploid eggs, a major cause of embryo death, genetic disorders, and infertility.
• Oocytes possess nuclear F-actin structures crucial for meiotic developmental capacity.

Purpose of the Study:

• To investigate the role and regulation of nuclear F-actin in oocyte health and meiotic development.
• To determine the correlation between nuclear F-actin levels and female reproductive aging.
• To elucidate the mechanisms of nuclear F-actin assembly and its impact on chromatin mobility and cytoplasmic organization.

Main Methods:

• Microscopy and live imaging to visualize F-actin structures within oocytes.
• Manipulation of G-actin monomer availability and transport between cytoplasm and nucleus.
• Assessment of meiotic progression and chromatin dynamics in response to altered F-actin organization.

Main Results:

• Nuclear F-actin structures are conserved in healthy mammalian oocytes and decrease with reproductive aging.
• Nuclear F-actin assembly is dependent on cytoplasmic G-actin monomer supply.
• Enriching the nucleus with G-actin promotes stable F-actin bundles and restricts chromatin mobility, while reduced nuclear import leads to detrimental cytoplasmic F-actin networks.

Conclusions:

• Nuclear F-actin plays a critical role in maintaining oocyte health and meiotic competence.
• The large oocyte nucleus is essential for regulating cytoplasmic F-actin organization.
• Defects in nuclear F-actin regulation are linked to age-related female infertility.