Abstract

Interspecific hybridisation has been demonstrated to produce offspring that exhibit advantageous traits; however, these offspring frequently exhibit reduced viability or infertility. The cattle-yak, a hybrid animal, is a natural model with which to study hybrid male sterility. The mechanism of male sterility in this species has not yet been fully elucidated. 79.88% of the differentially expressed genes were found to be significantly downregulated during the transition from gonocytes to spermatogonia in the cattle-yak. This resulted in an imbalance of proliferation and differentiation of spermatogonial stem cells in the cattle-yak, leading to a decrease in the number of spermatogonial stem cells. Over-expression of LIN28A has been demonstrated to promote the proliferation of undifferentiated spermatogonia in cattle-yak, primarily by means of up-regulating proliferation-related genes and down-regulating differentiation-related genes. Furthermore, the spermatogenic arrest in the cattle-yak was aggravated at the pachytene primary spermatocyte stage. During this stage, the chromosomes of primary spermatocytes exhibited excessive agglutination and subsequently underwent apoptosis, which ultimately resulted in the atypical configuration of the spermatogenic epithelium of the cattle-yak. The arrest of spermatogenesis in cattle-yak was originated from the transition from gonocytes to spermatogonia, resulting in the destruction of the balance of proliferation and differentiation of spermatogonial stem cells, and aggravated at the primary spermatocyte stage of pachytene, resulting in an absence of sperm in the spermatogenic epithelium.