Identification and functional characterization of developmental-stage-dependent piRNAs in Tibetan sheep testes

Abstract

The core function of the testes is to produce sperms, which is the prerequisite for maintaining male fertility. PIWI-interacting RNAs (piRNAs) are a class of non-coding small RNAs that are mainly enriched in the reproductive organ and play a key role in germ cell development and spermatogenesis. However, the expression and function of piRNAs in the testes of Tibetan sheep, a domestic animal endemic to the Tibetan Plateau, remain unknown. In this study, we evaluated the sequence structure, expression profile, and potential function of piRNAs in testicular tissues from Tibetan sheep at different developmental stages (3 months, 1 year, and 3 years of age, respectively) by small RNA sequencing. Of the identified piRNAs, the sequence lengths of 24-26 nt and 29 nt dominate. Most piRNA sequences begin with uracil and have a distinct ping-pong structure which mainly distributes in exons, repeat regions, introns, and other unannotated regions of the genome. The piRNAs in the repeat region are primarily derived from the retrotransposons: long terminal repeats (LTR), long interspersed nuclear elements (LINE), and short interspersed elements (SINE). These piRNAs constitute 2568 piRNA clusters, which mainly distribute on chromosomes 1, 2, 3, 5, 11, 13, 14 and 24, and of these clusters, a total of 529 piRNA clusters were differentially expressed in at least two age groups. Most of the piRNAs were expressed in a low abundance in the testes of developing Tibetan sheep. A total of 41552 and 2529 differential piRNAs were identified in testes from 3 months vs. 1 year, and 1 year vs. 3 years, respectively, presenting significant increased abundance for most piRNAs in 1 year and 3 years compared with 3 months. The functional evaluation of the target genes showed that the differential piRNAs are mainly involved in regulating gene expression, transcription, protein modification, and cell development during spermatogenesis and testicular development. In conclusion, this study focused on the sequence structure and expression characteristics of piRNAs in the testis of Tibetan sheep and provided new insights into the functional mechanism of piRNAs in testicular development and spermatogenesis of sheep.

Role and Mechanism of Epigenetic Regulation in the Aging of Germ Cells: Prospects for Targeted Interventions

“…Long intergenic ncRNA (lincRNA) deletions also reduced fertility in male C. elegans nematodes [71]. Interestingly, other studies showed that age-related differentially expressed piRNAs in spermatozoa are mainly involved in gene expression, transcription, protein modification, and cell development during spermatogenesis and testicular development [63,72].…”

Single-Cell Transcriptome Sequencing Reveals Molecular Expression Differences and Marker Genes in Testes during the Sexual Maturation of Mongolian Horses

“…Therefore, studying histomorphologic changes in the testis and the developmental pattern of spermatogenic cells is essential for controlling the reproductive process and regulating the fertility of animals. To date, study of testicular and spermatogenic epithelial cell development to control the developmental and reproductive stages of animals has been widely undertaken in mice, cats, pigs, sheep, and other animals [9][10][11][12]. In our research, we applied a similar approach to the genus Equus.…”