In most eukaryotes, meiotic homologous recombination (HR) is mediated by two recombinase systems, namely, the ubiquitous RAD51 and meiosis-specific DMC1. In the RAD51-mediated HR system, five paralogs are essential for normal RAD51 function. Meanwhile, given the embryonic lethality of RAD51 or any RAD51 paralog knockouts, the role of RAD51 in mammalian meiosis is unclear.

This study discovered a XRCC2 recessive point mutation leading to meiotic arrest, azoospermia and infertility in human and mice. Given that human and mice with the mutation survive and show no phenotypes other than reproductive defects, we believe that the point mutation is meiosis-specific and then represents an important step for scientists to investigate meiosis HR. (By Dr Yongjia Yang, https://jmg.bmj.com/content/early/2018/07/24/jmedgenet-2017-105145 )