Identification, cloning, and initial characterization of a novel mouse testicular germ cell-specific antigen

A monoclonal antibody, designated TES101, was raised by immunizing BALB/c m ice with an allogenic mouse testicular homogenate followed by immunohistoch emical selection as the initial screening method. By searching the expresse d sequence tag (EST) database with the N-terminal amino acid sequence of TE S101 reactive protein, we found that the predicted amino acid sequence enco ded by a mouse testicular EST clone matched the TES101 protein sequence. Se quence analysis of the clone revealed no homologous molecule in the DNA/pro tein database. Based on data obtained from N-terminal amino acid analysis o f the TES101 protein, the derived amino acid sequence contained a signal pe ptide region of 25 amino acids and a mature protein region of 225 amino aci ds, which translated into a protein with a molecular weight of 24 093. Nort hern blot analysis showed that mRNA of the TES101 protein was found in test is but not in any other mouse tissues examined. Western blot analysis revea led that TES101 reacted with a 38-kDa band on SDS-PACE under nonreducing co nditions, and this reactivity was abrogated under reducing conditions. Immu noelectron microscopic studies demonstrated that the molecule was predomina ntly located on the plasma membrane of spermatocytes and spermatids but not in Sertoli cells or interstitial cells, including Leydig cells. Thus, the TES101 protein is a novel molecule present primarily on the surface of deve loping male germ cells. TES101 protein may play a role in the processes und erlying male germ cell formation.