Molecular cloning of sheep and cashmere goat Pdia3 and localization in sheep testis

Protein disulphide isomerase family A3 (PDIA3) is a member of the protein disulphide isomerase (PDI) family and is multifunctional in many processes. Recently, it has been confirmed as a sperm membrane component and is implicated in sperm-egg fusion under which the molecular mechanism is still obscure. Protein disulphide isomerase family A3 cDNA has been cloned in several mammals; however, goat and sheep counterparts have not been identified. To facilitate the studies on the potential function of PDIA3 protein in sperm-egg fusion in sheep and goat, we cloned the cDNA encoding for Pdia3 of sheep (Ovis aries) and cashmere goat (Capra hircus) and studied its transcript and protein localization in sheep testis. The cloned sheep and cashmere goat Pdia3 cDNA are 1660 bp and 1591 bp, respectively. Bioinformatics analysis showed that sheep and goat Pdia3 cDNA both have a coding region of 1518 bp with the same nucleotides encoding the same 505 amino acids. The predicted peptide, with two typical motifs of Trp-Cys-Gly-His-Cys-Lys (WCGHCK) which is a hallmark of the PDI family, has high homology to that of bovine (99.21%), human (95.05%), rat (89.50%) and mouse (90.89%). Protein disulphide isomerase family A3 protein was observed in cells of various stages of spermatogenesis, from the primary spermatocyte to spermatozoa phases, as well as in the Leydig cells. It was observed in the entire sheep spermatozoa and mostly at the equatorial segment and the forepart of the flagellum. The Pdia3 mRNA was detected over the seminiferous epithelium in all stages of spermatogenesis.