Plays a role in spermatogenesis, where it is important for normal sperm head morphology. Also required for the acrosome reaction and thus normal male fertility. Specifically expressed in testis (at protein level). Not detected in other tissues tested (at protein level). In the testis, localizes to pachytene spermatocytes and spermatids. Detected from postnatal day 14 onwards. Maintained at high levels through to adulthood. No gross phenotype. Males have significantly reduced fertility. Testis weight, testis histology and sperm counts are normal. Approximately 25% of sperm have morphological defects in the sperm head and sperm nucleus, while morphology of the sperm flagellum appears normal. Capacitation-induced sperm motility is initially slightly reduced but then recovers. Frequency of both spontaenous and P4-induced acrosome reactions are significantly reduced. In an in-vitro fertilization assay, spermatozoa are able to bind and penetrate the oocyte perivitelline space but fertilizing capacity is severely impaired. Belongs to the CCDC87 family.