Meiosis-inducer required for the transition into meiosis for both female and male germ cells (PubMed:16461896, PubMed:17115059, PubMed:18799751, PubMed:18799790, PubMed:19805549, PubMed:32054698, PubMed:32032549). In female germ cells, acts downstream of ZGLP1 as a key effector of the meiotic program: required for premeiotic DNA replication and subsequent events in meiotic prophase (PubMed:16461896, PubMed:17115059, PubMed:18799751, PubMed:18799790, PubMed:32054698). During spermatogenesis, next to its role in meiotic initiation, promotes (but is not required for) spermatogonial differentiation (PubMed:25902548). In complex with MEIOSIN, directly activates the transcription of a subset of critical meiotic genes playing a central role in cell-cycle switching from mitosis to meiosis (PubMed:19805549, PubMed:32032549). Interacts with XPO1. Interacts with MEIOSIN (PubMed:32032549). Shuttles between nucleus and cytoplasm (PubMed:19805549). Nuclear export is XPO1-dependent (PubMed:19805549). Expressed exclusively in premeiotic germ cells in both sexes. In females, is expressed in the embryonic ovary. In males, is expressed in pubertal and adult testes, in premeiotic spermatogenic cells. Expressed by some type A and B spermatogonia, preleptotene spermatocytes, and early leptotene spermatocytes (at protein level). Expression begins in late undifferentiated spermatogonia and persists during differentiating spermatogonia (at protein level). Up-regulated in embryonic germ cells of the female gonads in an anterior-to-posterior wave from 12.5 dpc to 16.5 dpc. In male gonads, expression is first detected after birth. Up-regulated by retinoic acid in embryonic ovaries and adult testes, and by all-trans and 9-cis retinoic acid in P19 embryonic carcinoma (EC) cells. Transcription is repressed by DMRT1 in undifferentiated spermatogonia. Phosphorylated in P19 EC cells. Female and male mice are infertile due to severe gametogenesis impairment. In female mutant embryos, the initial mitotic development of germ cells is normal, but they fail to undergo promeiotic DNA replication and meiotic chromosome condensation. In male mutants, the premeiotic DNA replication is conserved and germ cells are able to partly condense chromosomes and initiate meiotic recombination. However, they fail to regularily continue over the leptotene stage of prophase I.