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. Associates with actin. However, does not bind F-actin directly. 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 (By similarity). Predominantly nuclear in nonconfluent cells (PubMed:16729964). Highly expressed in placenta, muscle, kidney and testis. Moderately expressed in heart, brain, lung, liver and intestine. Isoform 2 is widely expressed and expressed in fetal and adult testes, and spermatozoa. Up-regulated by all-trans-retinoic acid (ATRA) in retinal pigment epithelial cells (ARPE-19).