Genetic evidence suggests that Spata22 is required for the maintenance of Rad51 foci in mammalian meiosis

Meiotic nodules are the sites of double-stranded DNA break repair. Rpa is a single-stranded DNA-binding protein, and Rad51 is a protein that assists in the repair of DNA double strand breaks. The localisation of Rad51 to meiotic nodules before the localisation of Rpa in mice introduces the issue of whether Rpa is involved in presynaptic filament formation during mammalian meiosis. Here, we show that a protein with unknown function, Spata22, colocalises with Rpa in meiotic nodules in rat spermatocytes. In spermatocytes of Spata22-deficient mutant rats, meiosis was arrested at the zygotene-like stage, and a normal number of Rpa foci was observed during leptotene- and zygotene-like stages. The number of Rad51 foci was initially normal but declined from the leptotene-like stage. These results suggest that both formation and maintenance of Rpa foci are independent of Spata22, and the maintenance, but not the formation, of Rad51 foci requires Spata22. We propose a possible model of presynaptic filament formation in mammalian meiosis, which involves Rpa and Spata22.