In mice homozygous for the <i>Ter</i> mutation in the RNA-binding protein <i>Dnd1</i> (<i>Dnd1<sup>Ter/Ter</sup></i> ), many male germ cells (MGCs) fail to enter G1/G0 and instead form teratomas: tumors containing many embryonic cell types.
Through genetic studies in mice and pigs, we demonstrate that one such gonad-induced factor, the RNA-binding protein DAZL, is necessary in vivo to restrict the developmental potential of the germline; DAZL's absence prolongs expression of a <i>Nanog</i> pluripotency reporter, facilitates derivation of pluripotent cell lines, and causes spontaneous gonadal teratomas.