In elongated spermatids, enriched in the principal piece of flagella where it is peri-axonemal (PubMed:15489334). Disappears from sperm heads upon acrosome reaction (PubMed:15489334). Specifically expressed in testis (at protein level). Expression is detected at 3 weeks of postnatal development and persists up to adulthood (PubMed:27032685). Expressed in elongated spermatids but not detected in spermatogonia, spermatocytes, and round spermatids (PubMed:27032685). Extended N-terminus.