Disruption of BEND2 Leads to Impaired Oogenesis and Accelerated Reproductive Aging in Mice

Core Concepts

Disruption of the full-length BEND2 protein leads to reduced primordial follicle pool, impaired oocyte quality, and accelerated decline in female fertility in mice.

Abstract

This study investigates the role of the BEND2 protein in oogenesis and female reproductive aging using a novel Bend2 mutation in mice. Key highlights: BEND2 is highly expressed in the nuclei of spermatogenic cells during early meiotic prophase, independent of meiotic recombination. Disruption of the full-length BEND2 protein does not affect male fertility, but leads to increased apoptosis and persistent unrepaired DNA double-strand breaks (DSBs) in spermatocytes. In female mice, depletion of full-length BEND2 results in a significantly reduced primordial follicle pool established at birth, leading to fewer growing follicles and antral follicles during adulthood. Bend2 mutant females exhibit subfertility with smaller litter sizes, suggesting BEND2 is crucial for oocyte quality and ovarian reserve maintenance. The increased presence of unrepaired DSBs in Bend2 mutant oocytes is not directly linked to defects in meiotic recombination, but may involve regulation of LINE-1 retrotransposon activity. These findings reveal a critical role for BEND2 in oogenesis and provide insights into the genetic mechanisms underlying reproductive aging, which could be relevant for understanding human infertility.

Stats

Bend2Δ11/Δ11 females had significantly smaller litter sizes compared to wild-type females. The number of primordial follicles was significantly reduced in 1-week-old, 3-week-old, and 15-20-week-old Bend2Δ11/Δ11 females compared to controls. Bend2Δ11/Δ11 females had a significant reduction in the number of antral follicles at 15-20 weeks of age compared to controls. The number of MLH1 foci, marking crossover sites, was significantly lower in 1 dpp Bend2Δ11/Δ11 oocytes compared to controls.

Quotes

"Bend2Δ11/Δ11 females exhibited a more severe phenotype with a reduced ovarian reserve and subfertility, which had not been described before." "Our data shows that the depletion of BEND2 may lead to premature ovarian insufficiency (POI), which is also a significant cause of female infertility in humans, and its underlying genetic causes are mainly unknown."

Key Insights Distilled From

BEND2 is a crucial player in oogenesis and reproductive aging

by Huang,Y., Bu... at www.biorxiv.org 02-09-2024

https://www.biorxiv.org/content/10.1101/2024.02.06.579114v1

Deeper Inquiries

How might the regulation of LINE-1 retrotransposon activity by BEND2 contribute to the observed defects in oogenesis and ovarian reserve?

The regulation of LINE-1 retrotransposon activity by BEND2 could play a crucial role in the observed defects in oogenesis and the ovarian reserve. LINE-1 retrotransposons are known to cause DNA double-strand breaks (DSBs) during meiosis, which can impact genomic stability and integrity. In the context of oogenesis, increased LINE-1 activity can lead to an accumulation of DSBs, as observed in Bend2 mutant females. These unrepaired DSBs can disrupt meiotic progression, compromise chromosome synapsis, and impair crossover formation, ultimately affecting the quality and quantity of oocytes. The persistent unrepaired DSBs in Bend2 mutant females may lead to meiotic defects, reduced ovarian reserve, and subfertility. Therefore, the regulation of LINE-1 retrotransposon activity by BEND2 is likely essential for maintaining genomic stability during oogenesis and preserving the ovarian reserve.

What other cellular processes or pathways might BEND2 be involved in that could impact female fertility and reproductive aging?

Apart from its role in regulating LINE-1 retrotransposon activity, BEND2 may be involved in other cellular processes or pathways that could impact female fertility and reproductive aging. BEND2 is a BEN domain-containing protein that plays diverse roles in cellular processes such as transcriptional regulation, chromatin remodeling, and protein-protein interactions. In the context of female fertility, BEND2 may be involved in regulating gene expression patterns critical for oocyte development, folliculogenesis, and hormone signaling. It could also play a role in maintaining chromatin structure and integrity during meiosis, ensuring proper chromosome segregation and crossover formation. Additionally, BEND2 may interact with other proteins or pathways involved in DNA repair, cell cycle regulation, or epigenetic modifications that are essential for oocyte quality and reproductive aging. Further research is needed to elucidate the specific cellular processes and pathways through which BEND2 impacts female fertility and reproductive aging.

Given the relevance of BEND2 for human infertility, what strategies could be explored to potentially target BEND2 or its associated pathways for therapeutic interventions?

The relevance of BEND2 for human infertility highlights the potential for targeting BEND2 or its associated pathways for therapeutic interventions in individuals experiencing fertility issues. Some strategies that could be explored include: Pharmacological Interventions: Developing small molecule inhibitors or activators that target BEND2 or its interacting partners to modulate its function in oogenesis and reproductive aging. Gene Therapy: Exploring gene editing techniques, such as CRISPR/Cas9, to manipulate BEND2 expression or function in specific cell types relevant to fertility. Epigenetic Modulation: Investigating the epigenetic regulation of BEND2 and its impact on fertility, with a focus on modifying epigenetic marks to enhance reproductive potential. Targeted Drug Delivery: Designing targeted drug delivery systems to deliver therapeutic agents specifically to the reproductive organs or tissues where BEND2 functions are critical. Personalized Medicine Approaches: Utilizing genetic screening and personalized medicine approaches to identify individuals with BEND2-related infertility issues and tailor interventions based on their specific genetic profiles. By exploring these strategies and further understanding the role of BEND2 in human infertility, novel therapeutic interventions could be developed to address reproductive challenges and improve fertility outcomes in affected individuals.