Plays a role during spermatogenesis. Interacts with CRISP2. Localized to the peri-acrosomal region of the round spermatids as well as the heads and tails of the elongated spermatids and spermatozoa. Redistributed within the head during sperm capacitation. Additional isoforms seem to exist. Isoforms 3 and 4 are expressed in testis (at protein level). Isoforms 3 and 4 are first detected in testis from postnatal day 18 to adult.