Plays a role in acrosome expansion and establishment of normal sperm morphology during spermatogenesis. Important for male fertility. Primarily found in the equatorial segment of the acrosome (PubMed:22949614). The tyrosine phosphorylated protein localizes to a smaller region within the equatorial segment (By similarity). Also expressed weakly in the principal segment (By similarity). Testis specific (at protein level). Detected in testis from 3 weeks of age onwards. N-glycosylated. Males are sterile, while female fertility is not affected. Spermatozoa have significantly impaired swimming ability. The sperm head has a rounded shape instead of the normal hook-shaped morphology. The acrosome membrane does not associate normally with the nuclear envelope or intermediate filament bundles, and fails to expand along the nuclear surface. The sperm nucleus remains globular and mitochondria appear disorganized.