Identification of a testis specific polypeptide associated with spermatogenesis

Recenlly, we cloned a novel testis specific polypeptide, termed C2. from human and mouse testis eDNA libraries. The comparison of amino acid sequences of mouse C2 to human C2 indicated an identity of 80.6%. Homology in the amino terminus which contains 5 tandem leucine rich repeats spanning about 110 amino acids is about 93%. The leucine rich repeats are short sequence motifs present in a number of proteins with diverse functions and cellular locations in a variety of organisms. It is thought that these proteins are involved in prolein-protein interactions. In addition to leucine rich repeat domain, there are two regions in the mouse C2 amino acid sequence which are relatively rich in glutarnic acid. A hydrophobicity analysis indicated no transmembrane regions for the polypeptide. Northern blot analysis showed that C2 mRNA is expressed in mouse, rat, baboon, pig, and human testis, but not in any other tissue, in situ hybridization in mouse testis revealed that abundantly expressed mRNA is localized mainly in pachytene cells and round sperrntids. Developmental study has shown thal the mouse C2 mRNA begins to be transcripted from day 14 after birth. These data suggest a functional relationship of the 172 with spermatogenesis. The specific role of C2 in spermatogenesis and its exact biological significance remain to be established. This research was supported by NICHD through the Center for Recombinant Gamete Vaccinogens, Uniwwsity of Virginia.