DDX4 and Azoospermia: To characterise the DDX4C25-positive cells they were immunostained using a number of germline markers: DDX4 (using DDX4C25 antibody), PRDM1 (also known as BLIMP1; PR domain containing 1, with ZNF domain), DPPA3 (also known as STELLA; developmental pluripotency-associated 3), IFITM3 (also known as FRAGILIS; interferon induced transmembrane protein 3) and DAZL (deleted in azoospermia-like).