May be involved in spermatogenesis. Isoform 1 and isoform 3 interact with FANCL. Isoform 1 interacts with GGNBP1, ZNF403/GGNBP2 and OAZ3. Isoform 2 interacts with GGNBP1. Localizes along the nuclear membrane. Testis-specific. Specifically expressed in the germ cells and not in the somatic, Sertoli, or Leydig cells. In adult testis, expression starts in stage VIII pachytene spermatocytes, increases in stage IX and X pachytene spermatocytes, and culminates in stage XI diplotene spermatocytes and the meiotic cells in stage XII. Expression decreases slightly in step 1-3 spermatids, further decreases in step 4-11 spermatids, and is no longer detectable in step 12 spermatids and beyond. Isoform 2 is mainly expressed in testis. Isoform 2 is detected at high level in adult testis and at lower level in 19-day testis. Not detected in 14-day testis (at protein level). In the developing postnatal gonad, it is not expressed in 6-day-old testes in which the germ cells are almost exclusively spermatogonia or 14-day testis in which the most advanced germ cells are early pachytene spermatocytes. However, it is expressed in 21-day testis tubules containing late pachytene spermatocytes or spermatids. In the postnatal male testis, it is strictly confined to late pachytene spermatocytes through spermatids, a time during which meiosis takes place.