May play a role in fertility regulation. Testis-specific and age-dependent (at protein level). Highly expressed. Expressed in round spermatids located in the inner half-layer of the seminiferous epithelium as well as in early elongated spermatids having cytoplasmic protrusions into the tubular lumen. Detected at age 28 days and was most abundant at age 63 days. No expression at 21 days, seems therefore to be expressed in spermatids and not in spermatocytes or spermatogonia of the germ cells.