Abstract
The selection of testis size can improve the reproductive capacity of livestock used for artificial insemination and has been considered as an important strategy for accelerating the breeding process. Although much work has been done to investigate the mechanisms of testis development in various species, there is little information available in regard to the differences in transcriptomic profiling of sheep testes at different developmental stages. In this work, we aimed to identify differentially expressed genes (DEGs) by RNA-Seq in sheep during different growth stages, including 0 month old (infant, M0), 3 months old (puberty, M3), 6 months old (sexual maturity, M6) and 12 months old (body maturity, M12). A total of 4,606 (2,381 up and 2,225 down), 7,500 (4,368 up and 3,132 down), 15 (8 up and seven down) DEGs were identified in M3_vs_M0, M6_vs_M3, and M12_vs_M6 comparison, respectively. Of which, a number of genes were continuously up-regulated and down-regulated with testicular development, including ODF3, ZPBP1, PKDREJ, MYBL1, PDGFA, IGF1, LH, INSL3, VIM, AMH, INHBA, COL1A1, COL1A2, and INHA. GO analysis illustrated that DEGs were mainly involved in testis development and spermatogenesis. KEGG analysis identified several important pathways and verified several reproduction-associated DEGs such as COL1A1, COL1A2, PDGFA, and IGF1. In addition, two gene modules highly associated with testis development and core genes with testis size were identified using weighted gene co-expression network analysis (WGCNA), including hub genes positively associated with testis size such as RANBP9, DNAH17, SPATA4, CIB4 and SPEM1, and those negatively associated with testis size such as CD81, CSK, PDGFA, VIM, and INHBA. This study comprehensively identified key genes related to sheep testicular development, which may provide potential insights for understanding male fertility and better guide in animal breeding.
Highlights
The testis is a specific reproductive organ for male mammals to maintain male characteristics, produce sperm, and secrete androgenic hormones
We found 1951 out of 2,381 up-regulated genes were assigned to 6450 Gene Ontology (GO) terms, namely, 4,802 biological process (BP) terms, 622 cell component (CC) terms, and 1,026 molecular function (MF) terms
We found differentially expressed genes between different growth stages by RNA-Seq in sheep testes and identified the testicular development-related genes by functional enrichment
Summary
The testis is a specific reproductive organ for male mammals to maintain male characteristics, produce sperm, and secrete androgenic hormones. The development of mammalian testis is a highly complicated and sophisticated process This process is controlled by many factors and fundamentally orchestrated through the expression of thousands of protein-encoding genes, which are developmentally regulated during spermatogenesis and play pivotal roles during specific phases of germ cell development. A large number of differentially expressed genes (DEGs) were found to be functional in spermatogenesis and testicular development (Gong et al, 2013). The study on transcriptomic profiles of two porcine breeds during different testis development stages revealed genetic similarities and diversities of porcine testicular development, while the detailed molecular mechanisms underlying the gene similarities and diversities of spermatogenesis and testicular development of different pig breeds at different sexual mature ages require further studies (Li et al, 2016). A comparison of testicular transcriptomic profiles between fertile yak and infertile cattle-yak revealed that a large number of DEGs are associated with the male infertility of cattle-yak (Cai et al, 2017)
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