Plays a role in actin regulation at the ectoplasmic specialization, a type of cell junction specific to testis. Important for establishment of sperm polarity and normal spermatid adhesion. May also promote integrity of Sertoli cell tight junctions at the blood-testis barrier. Interacts with PALLD (PubMed:23565266). Associates with actin (PubMed:23565266). However, does not bind F-actin directly (By similarity). Associated with the cortical actin cytoskeleton structures in terminal web and cell-cell adhesion sites (By similarity). Highly expressed at the ectoplasmic specialization, an actin-rich cell junction specific to the testis (PubMed:23565266). Predominantly nuclear in nonconfluent cells (By similarity). Detected in testis where it is highly expressed in germ cells, and also expressed at lower levels in Sertoli cells (at protein level). In testis, first detected in stage VI seminiferous tubules where it is strongly expressed at the apical ectoplasmic speclialization (ES). Initially detected around the entire spermatid head, then during stage VII becomes tightly restricted to the concave side of the spermatid head. From late stage VIII through to stage XII, expressed once again around the entire spermatid head. In stage VIII-IX tubules, detected at lower levels at the basal ES associated with the blood-testis barrier. Detected at the apical spermatid-Sertoli cell junction in stage VIII-XII tubules. RNAi-mediated knockdown in testis tissue results in misorientation of spermatids, indicating loss of polarity. Transport of germ cells across the seminiferous epithelium is disrupted leading to partial spermatid entrapment in the epithelium. Premature spermatid release is also detected in stage VII tubules. F-actin is mislocalized and found on the convex side of the spermatid head, in contrast to wild type where it is tightly restricted to the concave side. PALLD localization is also abnormal, showing more diffuse expression away from the spermatid head.