100 PROTEOME OF BULL SPERMATOZOA

Abstract

The reproductive performance of a herd is the biggest factor affecting production and product quality of livestock. Thus, a decline of male fertility represents a dramatic economic loss in beef and dairy industries. Caused by molecular defects in the spermatozoa, uncompensatory infertility is a current challenge for the cattle industry, because even with normal sperm morphology, motility, and number, fertility of bulls is still sub-par. Thus, the objective of this study was to determine the global proteome of spermatozoa collected from bulls with different fertility and study the proteins playing a role in uncompensatory infertility. We performed difference gel electrophoresis (2D-DIGE) using cryopreserved sperm from a total of 6 bulls. Spermatozoa were thawed, purified by percoll gradient, and washed in PBS solution. For each bull, a pellet of 100 million sperm cells was resuspended in the 2D-DIGE labeling buffer, and the total protein was quantified. Cell lysates were separately labeled with CyDye DIGE Fluor dyes (and reciprocally with different dyes) and multiplexed in pairs on 3 gels. The samples were focused according to their isoelectric point through an Immobiline DryStrip, pH4-7, using a IPGphor 2, followed by separation on 12.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels (21.5–200 kDa) using a DALTsix. The resulting gels were scanned, and their topographic digital maps were used for algorithmic spot matching, background normalization, spot differences quantification, and elimination of artifacts (DeCyder 2-D Differential Analysis Software, GE Healthcare Life Sciences, Piscataway, NJ, USA). The results showed between 2600 and 2800 proteins with high confidence. Compared to the high-fertile bulls, 30 proteins were increased, and 27 were decreased in the low-fertility bulls within a 2-fold range. The largest significant increase and decrease were 3.97- and 2.4-fold, respectively. The identification of these differentially represented proteins is in progress. However, our results provided a panoramic view of sperm proteome from bulls of different fertility and thus paved the way for research on mechanisms of uncompensatory bull infertility.