Expression of the hamster sperm protein P26h during spermatogenesis

P26h is a hamster sperm protein of 26 kDa that has been previously characte rized as a surface protein covering the acrosome acquired during epididymal transit. P26h is involved in sperm-egg interactions. Recently, it has been shown that the P26h transcript is highly expressed in the testis, and the P26h cDNA has been cloned from a hamster testicular cDNA library. Herein we report the production of a fusion protein (maltose binding protein-P26h) w ith the whole P26h cDNA encoding sequence and the production of a polyclona l antiserum against it. In Western blots, this antiserum recognized both th e P26h extracted from cauda epididymal spermatozoa and the MBP-P26h. We als o determined the age of appearance of P26h and which germ cell types expres s P26h mRNA and its translational product. Northern blots and in situ hybri dization analysis showed that P26h transcripts appear at 3 wk of age, withi n the first round of spermatogenesis in the golden hamster. In situ hybridi zation showed that P26h transcripts are expressed in spermatocytes and roun d spermatids, whereas immunostaining revealed the presence of P26h in the c ytoplasm of round spermatids and elongated spermatids. P26h was undetectabl e in testicular spermatozoa. Both in situ hybridization and immunostaining showed P26h expression to be dependent of the testicular cell type and the epithelium cycle. The implications for P26h in sperm-egg interaction and th e testicular origin of P26h are discussed.