Comparative proteomic analysis of Taurine, Indicine, and crossbred (Bos taurus × Bos indicus) bull spermatozoa for identification of proteins related to sperm malfunctions and subfertility in crossbred bulls

Subfertility is one of the most common problems observed among Taurine × Indicine crossbred bulls in tropical countries; however, the etiology remain unknown in most of the cases. In present study, we compared the proteomic profile of spermatozoa from crossbred bulls (Bos taurus × Bos indicus) against their purebred parent lines (Holstein Friesian [Taurine] and Tharparkar [Indicine]) to find out alteration in expressions of proteins, if any. The proteomic profiles of freshly ejaculated spermatozoa from these breeds were compared by two-dimensional difference gel electrophoresis, and differentially expressed proteins were identified through mass spectrometry. It was observed that compared to Holstein Friesian, nine proteins were underexpressed and eight proteins were overexpressed (P < 0.05) in the spermatozoa of crossbred bulls. Similarly, four proteins were overexpressed and four proteins were underexpressed (P < 0.05) in the spermatozoa of crossbred bulls compared to Tharparkar bulls. In concurrent three breed comparison, 14 proteins were found to be differentially expressed (P < 0.05) between these breeds. From the findings of the study, it is apparent that the expression levels of several functionally significant proteins are either upregulated or downregulated in spermatozoa of crossbred bulls, which might be related to high incidence of subfertility in these bulls.