Contributes to normal sperm motility, but not essential for male fertility. Interacts with PRM2. Mainly nuclear. Also detected in cytoplasm near the midpiece of the flagellum. Predominantly expressed in testis. In testis: weakly expressed in newborns, increases remarkably at 3 weeks postpartum, and peaks at 2 months postpartum (at protein level). Belongs to the TDRP family. Extended N-terminus.