Genes Involved in Sperm Function: Investigation of the Expression of Hyal5 in the Male Reproductive Tract

Mesha Eaton
University of Delaware

SPAM1, the Sperm Adhesion Molecule 1, is a highly conserved sperm membrane protein with multiple essential roles in mammalian fertilization. This protein belongs to a group of closely linked hyaluronidases residing on mouse chromosome 6A2/human 7q31, and is responsible for the dissolution of the cumulus cells of the oocyte during fertilization. This is necessary to allow the sperm access to penetrate the zona pellucida of the oocyte. More recently a study of Spam1 knockout mice revealed that fertility was unaffected and suggested that this might be the result of the presence of a mouse-specific hyaluronidase, Hyal5, which has similar functions to Spam1 (Baba et. al., 2002). The goal of this study is to determine if Hyal5 is a redundant protein with respect to Spam1 which is expressed in the male reproductive tract. An mRNA expression analysis was performed using RT-PCR on both the testis and all three regions of the epididymis (caput, corpus, and cauda), which was rendered sperm-free after excessive washing. The results to date suggest the presence of Hyal5 mRNA in the cauda. Protein expression in the testis and epididymis show the presence of an identical isoform using Western analysis.
Immunohistochemical studies are in progress to determine the protein localization in the epididymis, efferent ducts and vas deferens.