MicroRNA profiles and potential regulatory pattern during the early stage of spermatogenesis in mice

Luo MM, Hao LL, Hu F, Dong YN, Gou LX, Zhang WD, Wang X, Zhao YH, Jia MC, Hu SN, Zhang XJ. MicroRNA profiles and potential regula- tory pattern during the early stage of spermatogenesis in mice. Sci China Life Sci MicroRNA profiles and potential regulatory pattern during the early stage of spermatogenesis in mice LUO MengMeng 2 HAO LiLi 1 HU Fen 2 DONG YaNan 2 GOU LiXia 2 ZHANG WenDian 0 WANG Xin 1 ZHAO YuHui 1 JIA MengChun 3 HU SongNian 1 ZHANG XiuJun 2 0 Hebei Normal University for Nationalities , Chengde 067000 , China 1 CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences , Beijing 100101 , China 2 College of Life Sciences, College of Psychology, Hebei United University , Tangshan 063000 , China 3 Department of Reproductive Endocrinology, National Research Institute for Family Planning , Beijing 100081 , China Spermatogenesis is a complicated and poorly understood process that relies on the precise regulation of the self-renewal and differentiation of spermatogonia. In many organisms, microRNAs (miRNAs) are involved in multiple developmental processes as critical regulators of transcriptional and post-transcriptional gene silencing. This study investigated the expression pattern of miRNAs in type B spermatogonia cells (BSc) and primary spermatocytes (PSc) of mice, using a high-throughput small RNA sequencing system. The results revealed that the expression levels of Let-7 family miRNAs were remarkably high in both cell types. Furthermore, the expression levels of miR-21, miR-140-3p, miR-103, miR-30a, miR-101b and miR-99b were decreased during the transformation from BSc to PSc. These miRNAs target vital genes that participate in apoptosis, cell proliferation and differentiation, junction assembly and cell cycle regulation. These results highlight the indispensable role of miRNAs in spermatogenesis. - Spermatogenesis is a complex process in which spermatogonial stem cells form spermatozoa following mitotic, meiotic and post-meiotic phases. The process of spermatogenesis is highly sensitive to fluctuations in the environment and involves numerous endocrine and paracrine signals to coordinate the self-renewal of spermatogonial stem cells (SCCs) and spermatogonial differentiation [1]. Spermatogenesis is characterized by the phase-specific expression of many genes that are exclusively expressed in spermatogenic cells. With the development and application of technologies such as gene cloning, gene expression and functional characterization, many spermatogenesis-related genes have been identified in the past few years, some of which were found to play important roles in spermatogenesis [2]. Spermatogenesis-associated genes such as cyclins, proto-oncogenes and genes for azoospermia factor, cytoskeleton, heat shock proteins, nucleoprotein transition, centrin and apoptosis are involved in highly conserved landmark events such as meiotic recombination, formation of the synaptonemal complex, sister chromatid cohesion, spermiogenesis during post© The Author(s) 2014. This article is published with open access at link.springer.com meiotic stages, and checkpoints and factors required for the meiotic cell cycle. Recently, small RNA molecules, including small interfering RNAs (siRNAs), microRNAs (miRNAs, approximately 22-nt sequences) and Piwi-interacting RNAs (piRNAs, 24- to 30-nt sequences) have emerged as important regulators of gene expression at the post-transcription or translation level [3]. Several miRNAs are expressed abundantly in male germ cells, either throughout or during specific stages of spermatogenesis [4]. piRNAs, which are actively involved in retrotransposon silencing that protects the integrity of the genome, are only present in pachytene spermatocytes and round spermatids [5]. piRNAs in type A spermatogonia, pachytene spermatocytes and round spermatids were profiled by deep sequencing in a recent study, the results showed that piRNA mapping to retrotransposons, mRNAs and intergenic regions had different length distributions and were differentially regulated in spermatogenesis [6]. In a recent study, mature mouse sperm were found to be extremely enriched in a novel class of tRNA-derived small RNAs (29–34 nt), which were slightly different from the RNA found in adult testes (26–32 nt). The discovery of sperm-borne RNAs have opened the possibility of additional paternal contributions aside from providing DNA [7]. miRNAs are a family of 21–25-nt cellular non-coding RNAs that bind to the 3′-untranslated region (UTR) of cognate mRNA through an imperfect match to repress their translation and stability [8, 9]. This is achieved by forming a ribonucleoprotein complex termed the RNA-induced silencing complex (RISC), which contains a member of the Argonaute family [10]. Recently, the fields of research on stem cells and miRNA have converged with the identification of stem cell-specific miRNAs [11,12]. Based on their function in translation atte (...truncated)