NANOS3 and teratoma: This might be because the PGCs undergo apoptotic cell death [26] or transdifferentiate into somatic cells as observed in other species [27, 28] during migration stages in the absence of Nanos3. In contrast, a small number of PGCs were still observed in the male gonads of Dnd1Δ/Δ embryos (Fig 5D), suggesting that some of these survivor cells eventually acquire pluripotency at the late stages of embryogenesis and then develop to form teratomas after birth.