Plays a key role in meiotic progression (PubMed:19686734, PubMed:21079677, PubMed:21478856). Regulates 3 different functions during meiosis: ensures that sufficient numbers of processed DNA double-strand breaks (DSBs) are available for successful homology search by increasing the steady-state numbers of single-stranded DSB ends (PubMed:19686734, PubMed:21079677). Promotes synaptonemal-complex formation independently of its role in homology search (PubMed:19686734, PubMed:21079677). Plays a key role in the male mid-pachytene checkpoint and the female meiotic prophase checkpoint: required for efficient build-up of ATR activity on unsynapsed chromosome regions, a process believed to form the basis of meiotic silencing of unsynapsed chromatin (MSUC) and meiotic prophase quality control in both sexes (PubMed:21478856). Interacts with HORMAD2 (PubMed:22549958). Interacts with IHO1 (PubMed:27723721). Preferentially localizes to unsynapsed or desynapsed chromosomal regions during the prophase I stage of meiosis (PubMed:19851446, PubMed:19686734, PubMed:27723721). Accumulates on the chromosomes during the leptotene to zygotene stages of meiotic prophase I (PubMed:19851446, PubMed:19686734, PubMed:27723721). As germ cells progress into the pachytene stage, disappears from the synapsed chromosomal regions (PubMed:19851446, PubMed:19686734, PubMed:27723721). Once the chromosomes desynapse during the diplotene stage, it again accumulates on the chromosome axis of the desynapsed homologs (PubMed:19851446, PubMed:19686734, PubMed:27723721). TRIP13 is required for depletion from synapsed chromosomes (PubMed:19851446). The expression of the phosphorylated form at Ser-375 is restricted to unsynapsed chromosomal regions (PubMed:22346761). Specifically expressed in meiotic germ cells. Expressed in spermatocytes from P10 to adulthood. Expressed in oocytes from 12.5 dpc to P9. Primarily detected in spermatocytes and less in spermatids or spermatogonia. Abundant in the nuclei of pachytene and zygotene cells. Also detected in nuclei of diplotene cells (at protein level). Phosphorylated at Ser-375 in a SPO11-dependent manner. Mice develop normally without obvious somatic defects but males and females are sterile. Although spermatocytes are present in testis tubules at epithelial cycle stage III-IV, they undergo apoptosis by the end of stage IV, and post-meiotic cells are not found in testes, suggesting that spermatocytes are eliminated at a stage equivalent to mid-pachytene. In females, ovarian development is grossly normal, eggs fertilize and embryonic development arrests at blastocyst stage due to aneuploidy.