A novel endozepine-like peptide (ELP) is exclusively expressed in male germ cells

Abstract

A cDNA clone encoding a novel endozepine-like peptide (ELP) was isolated from mouse testes, sequenced, and its mRNA expression characterized by northern and in situ hybridization. ELP mRNA was found exclusively in the late spermatid stages of spermatogenesis in the testes of sexually mature mice and in no other tissue or cell type examined. It was also expressed in rat, bovine, porcine and sheep testes. Mouse ELP-encoding cDNA was used to construct expression vectors for the production of ELP in bacteria, and the purified bacterial protein used to raise polyclonal antibodies in rats. These antibodies identified the predicted endogenous ELP in extracts of mouse testis and epididymis and in no other tissue. Immunohistochemistry confirmed that the ELP antigen was present only in late spermatids and spermatozoa, particularly within the cytoplasmic droplet which is retained by the mature spermatozoa during their transit into the epididymis. We conclude that ELP is an intracytoplasmic peptide exclusively expressed in post-meiotic spermatozoa and which may be involved in the energy metabolism of the mature sperm.