Comparative iTRAQ proteomics revealed proteins associated with spermatogenic arrest of cattleyak

Male infertility of cattleyak due to spermatogenic arrest greatly restricts their effective utilization in yak breeding. Although much work has been done to investigate the mechanisms of spermatogenic arrest, there is no information regarding the differences of protein composition between cattleyak and yak testis. Comparative investigation of testis proteomes between cattleyak and yak using iTRAQ proteomics identified 256 differentially abundant proteins with fold change values higher than ±1.5. Most of the differentially abundant proteins were involved in extracellular matrix organization, response to stimulus, metabolic and cellular process, in which a large number of the cattleyak predominant proteins were associated with various stresses, cell adhesion and germ cell migration. Such upregulated proteins as integrins and their ligands in the extracellular matrix involved in ECM-receptor interaction pathway may help germ cells to endure pulling forces and impede their migration. In contrast, down-regulated proteins in cattleyak were associated with defects in various metabolic processes and cellular processes during spermatogenesis. Such Downregulated proteins as the subunits of mitochondrial cytochrome Bc1 complex involved in the Alzheimer's disease and oxidative phosphorylation pathways may lead to mitochondrial dysfunction and cell death in cattleyak testis.

Spermatogenic arrest of cattleyak involves defects of both germ cells and their micro-environment in testis. In this study, Dozens of proteins possibly associated with spermatogenic arrest of cattleyak were identified by comparative iTRAQ proteomics, in which a large number of the cattleyak predominant proteins may act in response to various stresses (especially inflammatory stresses), enhance cell adhesion and impeded germ cell migration, while down-regulated proteins in cattleyak were associated with defects in various metabolic processes and cellular processes during spermatogenesis. Therefore, germ cells in testis of cattleyak may be constantly in a stress state (similar to inflammation) due to accumulation of some toxic intermediate products resulted from metabolic disturbances. Metabolic defects of germ cells and their deleterious micro-environment in testis of cattleyak may be the root of all other problems during spermatogenesis.