Required for spermatogenesis and is involved in the suppression of retrotransposon transcription in male germ cells. Expressed abundantly in adult testis, at moderate levels in unfertilized eggs and ovaries and weakly in embryonic stem cells. In the male gonad, barely detected at 13.5 dpc or at birth, detected weakly on postnatal day 14 and maximally expressed in the 4- or 7-week-old mouse testis but not detected in the epididymis of the 7-week-old mouse (at protein level). In the female gonad, low levels detected at birth (at protein level). In the adult testis, present predominantly in pachytene spermatocytes and round spermatids but not in spermatogonia, preleptotene spermatocytes or elongating spermatids (at protein level). Mutant mice grow normally and appear healthy but males are sterile due to massive germ cell apoptotic death after postnatal day 14 with meiocytes ceasing meiotic progression before the early meitoic phase. There is also increased transcription of LINE-1 and IAP retrotransposons accompanied by demethylation of their promoter regions. Belongs to the UPF0224 (FAM112) family.