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Updated: Oct 7, 2025

Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
Published on: July 18, 2025
RAD51AP2 is required for efficient meiotic recombination between X and Y chromosomes
Hui Ma1, Tao Li1, Xuefeng Xie1
1Division of Reproduction and Genetics, First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at Microscale, School of Basic Medical Sciences, Division of Life Sciences and Medicine, CAS Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, 443 Huangshan Road, Hefei 230027, China.
Abstract:
Faithful segregation of X and Y chromosomes requires meiotic recombination to form a crossover between them in the pseudoautosomal region (PAR). Unlike autosomes that have approximately 10-fold more double-strand breaks (DSBs) than crossovers, one crossover must be formed from the one or two DSBs in PARs, implying the existence of a sex chromosome–specific recombination mechanism. Here, we found that RAD51AP2, a meiosis-specific partner of RAD51, is specifically required for the crossover formation on the XY chromosomes, but not autosomes. The decreased crossover formation between X and Y chromosomes in Rad51ap2 mutant mice results from compromised DSB repair in PARs due to destabilization of recombination intermediates rather than defects in DSB generation or synapsis. Our findings provide direct experimental evidence that XY recombination may use a PAR-specific DSB repair mechanism mediated by factors that are not essential for recombination on autosomes.
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