TNP1 Functional SNPs in bta-miR-532 and bta-miR-204 Target Sites Are Associated with Semen Quality Traits in Chinese Holstein Bulls1

Transition nuclear proteins (TNPs), major proteins found in the chromatin of condensing spermatids, have been implicated in spermatogenesis and male fertility. In this study, DNA samples were collected from 404 Chinese Holstein bulls and sequenced to identify genetic variants in the 3'-untranslated region (UTR) of TNP1 and to investigate genetic variations in the TNP1 gene and their common haplotypes. This study was also conducted to determine whether these variations affect bovine semen quality traits and expression levels by PCR-restriction fragment length polymorphism, bioinformatics analyses, quantitative real-time PCR (qPCR), and fluorescence assay. Results showed that one new single-nucleotide polymorphism (SNP; g. 528 G>A, ss1388116558) and one reported SNP (g. 442 A>G, rs110469441) were found in the 3'-UTR of the TNP1 gene. Bioinformatics analysis results revealed that both loci were located in bta-miR-532-binding and bta-miR-204-binding regions, respectively. Association studies revealed that bulls with H1H1 (AGAG) and H1H3 (AGGG) haplotype combinations exhibited a lower deformity rate than those with other haplotype combinations (P < 0.05). The qPCR results showed that the relative mRNA expression of TNP1 in bulls with H1H1 haplotype combination was significantly higher than that in bulls with H4H4 haplotype combination (P < 0.05). MicroRNA qPCR results suggested that bta-miR-532 expression was downregulated by 5-fold in adult bull testicular tissues compared with that in fetal bull testicular tissues; by contrast, bta-miR-204 expression was downregulated by 1.6-fold. Luciferase assay results also indicated that TNP1 expression was directly targeted by bta-miR-532 and bta-miR-204 in murine Leydig tumor cell lines. These results provide the first indication of g. 442 A>G-mediated and g. 528 G>A-mediated translational suppression in which SNPs altered the binding of bta-miR-204 and bta-miR-532 to the 3'-UTR of TNP1; the mediated translational suppression could be involved in the regulation of TNP1 expression and may influence the morphological characteristics of Chinese Holstein bull sperm. We propose that SNPs on the TNP1 3'-UTR may help select semen quality trait in Chinese Holstein bulls in the dairy industry.