Comparative proteomic analysis identifies differentially expressed proteins associated with meiotic arrest in cattle-yak hybrids.

Cattle-yak, the interspecific hybrid between yak and taurine cattle, exhibits male-specific sterility. Massive loss of spermatogenic cells, especially spermatocytes, results in azoospermia in these animals. Currently, the mechanisms underlying meiosis block and defects in spermatocyte development remain elusive. The present study was designed to investigate the differences in the protein composition of spermatocytes isolated from 12-month-old yak and cattle-yak testes. Histological analysis confirmed that spermatocytes were the most advanced germ cells in the testes of yak and cattle-yak at this developmental stage. Comparative proteomic analysis identified a total of 452 differentially abundant proteins (DAPs) in the fluorescence-activated cell sorting (FACS) isolated spermatocytes from cattle-yak and yak. A total of 291 proteins were only present in yak spermatocytes. Gene Ontology analysis revealed that the downregulated DAPs were mostly enriched in the cellular response to DNA damage stimulus and double-strand breaks (DSBs) repair via break-induced replication, while the proteins specific for yak were related to cell division and cycle, spermatogenesis, and negative regulation of the extrinsic apoptotic signaling pathway. Ultimately, these DAPs were related to the critical process for spermatocyte meiotic events, including DSBs, homologous recombination, synapsis, crossover formation, and germ cell apoptosis. The database composed of proteins associated with spermatogenesis, including KPNA2, HTATSF1, TRIP12, STIP1, LZTFL1, LARP7, MTCH2, STK31, ROMO1, CDK5AP2, DNMT1, RBM44, and CHRAC1, is the focus of further research on male hybrid sterility. In total, these results provide insight into the molecular mechanisms underlying failed meiotic processes and male infertility in cattle-yak.