Histological Comparison and Transcriptome Analysis of Testes of Duroc and Meishan Boars

Chinese indigenous boars have some unusual endocrine and physiological attributes, such as earlier sexual maturity, thereby providing a valuable animal model for study of the mechanism of boar sexual development and sperm production. In this study, the histological structures and transcriptomes of testes of 20-day, 75-day, 270-day Duroc and Meishan boars were compared and analyzed. The diameter of seminiferous tubules was significantly different at different development stages of two breeds. Some primary and secondary spermatocytes, spermatids and sperms have appeared in the seminiferous tubules of 75-day Meishan boars, but not in 75-day Duroc boars. The number of Sertoli cells in 20-day Meishan boars was significantly higher than 20-day Duroc boars (P <0.01), while it was lower in Meishan boars than Duroc boars at 75 and 270 days. Meanwhile RNA-seq was used to gain insights into transcriptomes of testes of Duroc and Meishan boars. More than 70M high-quality reads with 88.19%-95.49% of raw reads were obtained. For comparisons of any two samples, we normalized 20,524 genes and filtered out 2,724–11,111 significantly differentially expressed genes (FDR ≤0.001, |log2Ratio|≥1) in each comparison. To identify signature genes for regulation of sexual maturity and spermatogenesis, we clustered a set of DEGs to show expression pattern about the differentially expressed genes in different samples, the clustering showed that the expression patterns of D20, D75 and M20 were similar, while the expression patterns of M75, M270 and D270 were similar. In addition, pathway analyses defined seven pathways significantly involved in male sexual function regulation. In addition, four main alternative splicing event and large number of novel transcripts were detected, and 188,708 and 324,334 SNPs were detected from testes of Duroc and Meishan boars respectively.