May be involved in spermatogenesis. Isoform 1 is testis-specific. Isoform 2 is expressed in heart, brain, skeletal muscle, kidney, pancreas, lung, liver and testis. Isoform 3 is expressed in heart, liver, and kidney. Expression was first detected at postnatal day 6, and reached the adult level between postnatal day 14 and 21.