Binds to target gene promoters, including NKX2-5 and SYCE1, but not GATA4, and may be involved in the maintenance of the active epigenetic status of these genes. Interacts with DPPA4. Not detected in adult tissues. Expressed in 4-cell embryo, morula and blastocyst. At 7.5 dpc, detected in the epiblast. At 10.0 dpc, expressed in the primordial germ cells. Expression decreases at 12.0 dpc in the embryonic gonads. At 14.5 dpc, expression is restricted to testis. 6 days after birth, still detected in primitive type A spermatogonia. Expressed in undifferentiated embryonic stem cells, but expression rapidly decreases upon differentiation. Mutant animals show survival rates similar to wild-type until 16.5 dpc. Then mortality increases and no animals survive beyond weaning age. At 18.5 dpc, the lungs of mutants mice show a thicker mesenchyme and smaller alveolar space than those of wild-type animals.