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The number of Sertoli cells in the testis is a major regulator on the sperm production capacity. MicroRNAs (miRNAs) participate in regulating the proliferation and apoptosis of porcine immature Sertoli cells. However, the functions and mechanisms of action of most identified miRNAs in porcine Sertoli cells remain largely unknown. In the present study, based on our previous results from an EdU-based high-content screening assay, we further studied the mechanism of action of miR-191 on the proliferation and apoptosis of porcine immature Sertoli cells through flow cytometry, Western blotting, and dual-luciferase activity analyses. The results demonstrated that overexpression of miR-191 promoted cell cycle progression from G 1 phase to the S and G 2 phases, enhanced cell proliferation, and inhibited apoptosis in the porcine immature Sertoli cells, whereasmiR-191 inhibition resulted in the opposite effects. The results from a luciferase reporter assay showed that miR-191 directly targeted the 3'-UTR of theBDNF gene. BDNF knockdown also promoted cell cycle progression to the S phase, cell proliferation and inhibited cell apoptosis, which were consistent with the effects of the miR-191overexpression. A co-transfection experiment showed that BDNF knockdown abolished the effects of miR-191 inhibition. Furthermore, both miR-191 overexpression and BDNFinhibition elevated the phosphorylation of PI3K and AKT, the key components of the PI3K/AKT signaling pathway, whereas BDNFinhibition offset the effects of the miR-191 knockdown. Overall, these data indicated that miR-191 promotes cell proliferation and inhibits apoptosis in porcine immature Sertoli cells by targeting theBDNF gene through activating the PI3K/AKT signaling pathway. This study provides a novel scientific basis for further investigation on the biological functions of miR-191 on porcine spermatogenesis.

Genomic selection is a form of marker-assisted selection in which genetic markers covering the entire genome are used so that all quantitative trait loci are in linkage disequilibrium with at least one marker. Genomic selection improves the efficiency and accuracy of breeding and it is widely used in purebred breeding across many animal species. However, some studies indicate that the accuracy of genome selection in cross breeding needs to be improved,especially in cross population. As one of the most extensive breeding methods employed in the swine industry, cross breeding has significant, potential research and economic value to further improve its performance by combining with genomic selection. In this review, we summarize the application of genomic selection in pigs, and elucidate the genomic selection deficiencies in breeding hybrid pigs. This review will also provide valuable insights for the future application and improvement of genomic selection in pig cross breeding.

In testicular tissue, immature Sertoli cell proliferation ability determines the size of mature Sertoli cell populations, which further regulates the spermatogenesis in the adult male animals. Studies have demonstrated that microRNAs (miRNAs) participate in the regulation of the immature Sertoli cell proliferation and apoptosis, but the functions of most identified miRNAs remain unclear. In this study, based on previous RNA-seq results, we analyzed the regulatory role (s) of miR-362 in proliferation and apoptosis of porcine immature Sertoli cells. The ZFN644 gene was predicted to be a target gene of miR-362 using bioinformatics methods. The expression levels of miR-362 and ZNF644 gene were measured using qRT-PCR assay in developing porcine testicular tissues and in immature Sertoli cells transfected with either miR-362 mimic or miR-362 inhibitor. The dual luciferase reporter assay was used to determine the regulatory relationship between miR-362 and ZNF644. The results showed that a putative target site of miR-362 was located in the 3'UTR of ZNF644. The expression of miR-362 was significantly and negatively correlated with ZNF644 expression in the developing porcine testicular tissues. Co-transfection of miR-362 and psiCHECK2-ZNF644-WT 3'UTR luciferase vector significantly suppressed luciferase activity. The ZNF644 gene expression level was significantly regulated by miR-362, demonstrating that miR-362 targets ZNF644 gene and inhibits its expression in porcine immature Sertoli cells. Flow cytometry, CCK8, and EdU assays were used to measure the effects of over-expression of miR-362 or knockdown of ZNF644 on porcine immature Sertoli cell proliferation; Annexin V-FITC/PI staining assays and qRT-PCR technology were used to test the apoptosis and the expression levels of cell survival-related genes, respectively. Over-expression of miR-362 and knockdown of ZNF644 arrested the porcine immature Sertoli cells in G 1 and G 2 phases of the cell cycle, respectively, and inhibited proliferation, enhanced apoptosis in the porcine immature Sertoli cells, and significantly regulated the expression levels of cell survival-related genes. Taken together, these data indicate that miR-362 inhibits proliferation and promotes apoptosis in porcine immature Sertoli cells by targeting the ZNF644 gene, thereby providing the scientific basis for further study on the function(s) of miR-362 in the porcine spermatogenesis.

Ubiquitin-proteasome pathway (UPP) is the main pathway of protein degradation in eukaryotic cells. The UPP plays very important roles in cell cycle progression, apoptosis, stress response and growth and development through regulating protein interaction, protein activity, protein localization and signal transduction. Previous studies have shown that the UPP is essential for regulating acrosome and tail biogenesis during spermatogenesis in human and animals. The dysregulation of UPP during spermatogenesis results in sperm deformity and reduced sperm motility and leads to reproductive system diseases such as oligospermatism, infertility and testicular tumors. In this review, we summarized the signal transduction and regulation mechanism of UPP in spermatogenesis, which may provide references for future studies.