DND1 and testicular germ cell tumor: DND1, an evolutionary conserved RNA-binding protein (RBP) (10, 11), is necessary for the differentiation of primordial germ cells (PGCs) and the suppression of germ cell tumors and plays a vital role in regulating male germ cell development (12) through the interplay with Nanos2 and Nanos3 (13, 14).