Transcription factor that binds preferentially to the octamer motif (5'-ATGTTAAT-3'). May exert a regulatory function in meiotic events that are required for terminal differentiation of male germ cell. Highly restricted to adult testis. Expressed transiently immediately prior to meiosis I during spermatogenesis in the male germ cell. Belongs to the POU transcription factor family. Class-5 subfamily.