Strikingly, we found that H2Aub, a repressive histone mark catalyzed by PRC1, decreased in wild-type testes specifically at the spermatocyte stage; H2Aub was bright in spermatogonia and somatic cyst cells throughout the testis, but H2Aub signal declined dramatically in spermatocytes (Fig. S4A,B). Here, PRC1 is linked to cyst.