TopBP1 deficiency impairs the localization of proteins involved in early recombination and results in meiotic chromosome defects during spermatogenesis.

Topoisomerase IIβ-binding protein 1 (TopBP1) is BRCT domain-containing protein that is required for DNA double-strand break (DSB) repair and DNA damage responses; however, its function during the early stage of spermatogenesis is still unclear. To investigate the physiological role of TopBP1, we have generated germ cell-specific TopBP1-depleted mouse model. TopBP1-deleted mice were infertile, showed a loss of germ cells and had meiotic defects. Conditional TopBP1 deletion resulted in reduced testis size, reduced number of epididymal sperm, increased apoptosis, and severely compromised fertility. TopBP1 deficiency caused defects in DMC1 and Rad51 foci formation, abnormal synaptonemal complexes and meiotic chromosome defects. Collectively, these results suggest that TopBP1 deficiency during spermatogenesis impairs the localization of proteins involved in early recombination at DSBs, results in meiotic chromosome defects and leads to infertility.