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Updated: Aug 16, 2026
Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
Published on: July 18, 2025
Surveillance of different recombination defects in mouse spermatocytes yields distinct responses despite elimination
Marco Barchi1, Shantha Mahadevaiah, Monica Di Giacomo
1Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
Abstract:
Fundamentally different recombination defects cause apoptosis of mouse spermatocytes at the same stage in development, stage IV of the seminiferous epithelium cycle, equivalent to mid-pachynema in normal males. To understand the cellular response(s) that triggers apoptosis, we examined markers of spermatocyte development in mice with different recombination defects. In Spo11(-)(/)(-) mutants, which lack the double-strand breaks (DSBs) that initiate recombination, spermatocytes express markers of early to mid-pachynema, forming chromatin domains that contain sex body-associated proteins but that rarely encompass the sex chromosomes. Dmc1(-)(/)(-) spermatocytes, impaired in DSB repair, appear to arrest at or about late zygonema. Epistasis analysis reveals that this earlier arrest is a response to unrepaired DSBs, and cytological analysis implicates the BRCT-containing checkpoint protein TOPBP1. Atm(-)(/)(-) spermatocytes show similarities to Dmc1(-)(/)(-) spermatocytes, suggesting that ATM promotes meiotic DSB repair. Msh5(-)(/)(-) mutants display a set of characteristics distinct from these other mutants. Thus, despite equivalent stages of spermatocyte elimination, different recombination-defective mutants manifest distinct responses, providing insight into surveillance mechanisms in male meiosis.
Insights
Different recombination defects trigger male meiosis apoptosis at the same stage. However, distinct cellular responses, including DNA double-strand break (DSB) repair pathways and checkpoint proteins like TOPBP1, are involved.
Area of Science:
- Reproductive Biology
- Molecular Genetics
- Cell Biology
Background:
- Meiotic recombination is essential for accurate chromosome segregation during spermatogenesis.
- Defects in recombination can lead to male infertility due to spermatocyte apoptosis.
Purpose of the Study:
- To investigate the distinct cellular responses and surveillance mechanisms underlying spermatocyte apoptosis caused by different recombination defects.
- To understand the roles of specific proteins, such as TOPBP1 and ATM, in male meiotic checkpoints.
Main Methods:
- Analysis of spermatocyte development markers in mouse mutants with defects in double-strand break (DSB) formation (Spo11) or repair (Dmc1, Atm, Msh5).
- Epistasis analysis and cytological examination of chromatin organization and protein localization.
- Assessment of meiotic progression and apoptosis at stage IV of the seminiferous epithelium cycle.
Main Results:
- Spo11(-/-) spermatocytes show early to mid-pachynema markers without encompassing sex chromosomes.
- Dmc1(-/-) and Atm(-/-) spermatocytes arrest earlier (late zygonema), implicating unrepaired DSBs and the TOPBP1 checkpoint protein.
- Msh5(-/-) mutants exhibit unique characteristics, distinct from other recombination-defective mutants.
Conclusions:
- Despite occurring at the same developmental stage, spermatocyte apoptosis results from diverse cellular responses to distinct recombination defects.
- These findings reveal complex surveillance mechanisms in male meiosis that monitor DNA double-strand break repair and recombination progression.
