Abstract
Sub-fertility is one of the most common problems observed in crossbred males, but the etiology remains unknown in most of the cases. Although proteomic differences in the spermatozoa and seminal plasma between breeds have been investigated, the possible differences at the sperm precursor cells and supporting/nourishing cells have not been studied. The present study reports the differential proteomic profile of spermatogenic and Sertoli cells in crossbred and purebred bulls. Testis was removed by unilateral castration of 12 peri-pubertal bulls (10 months age), four each from crossbred (Holstein Friesian × Tharparkar), exotic purebred [Holstein Friesian (HF)] and indigenous purebred [Tharparkar (TP)] bulls. Spermatogenic and Sertoli cells were isolated and subjected to proteomic analysis. Protein extracts from the Sertoli and spermatogenic cells of each breed were analyzed with 2-dimensional difference gel electrophoresis (2D-DIGE) and analyzed with Decyder™ software. Compared to HF, 26 protein spots were over expressed and 14 protein spots were under expressed in spermatogenic cells of crossbred bulls. Similarly, 7 protein spots were over expressed and 15 protein spots were under expressed in the spermatogenic cells of TP bulls compared to that of crossbred bulls. Out of 12 selected protein spots identified through mass spectrometry, Phosphatidyl ethanolamine binding protein was found to be over expressed in the spermatogenic cells of crossbred bulls compared to TP bulls. The protein, gamma actin was found to be over expressed in the Sertoli cells of HF bulls, whereas Speedy Protein-A was found to be over expressed in Sertoli cells of crossbred bulls. It may be concluded that certain proteomic level differences exist in sperm precursor cells and nourishing cells between breeds, which might be associated with differences in the fertility among these breeds.
Highlights
Sub-fertility and poor semen quality are the important reasons of dairy bull wastage and the magnitude of these problems are high in crossbred bulls (Vijetha et al, 2014)
Since the numbers of Sertoli cells are fixed around the time of puberty (Wang et al, 1989) and sperm production starts after puberty, we studied the proteomics of Sertoli and spermatogenic cells in peri-pubertal bulls
14 proteins were found over expressed in the spermatogenic cells isolated from Holstein Friesian (HF) bulls, whereas 26 protein spots were under expressed in HF compared to crossbred bulls (Table 1)
Summary
Sub-fertility and poor semen quality are the important reasons of dairy bull wastage and the magnitude of these problems are high in crossbred bulls (Vijetha et al, 2014). The males produced through crossing of Bos taurus with Bos indicus suffer from serious infertility/sub-fertility problems (Mukhopadhyay et al, 2010). The seminal parameters and fertility of the crossbred bulls have been reported to be poor than the indigenous breeds (Khatun et al, 2013). The reason for production of low quality semen in crossbred bulls, even during the best breeding season, has yet to be identified. It is well known that production of fertile sperm is a consequence of normal mitosis and meiosis of germ cell and proper function of germ and Sertoli cells (Johnson, 1991). Sub-fertility and poor semen quality may be attributed to impaired spermatogenesis, endocrine disturbances and alterations in micro-environment of seminiferous tubules (Robaire and Viger, 1995; Hinton and Palladino, 1996)
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