MicroRNA-34b-5p targets PPP1R11 to inhibit proliferation and promote apoptosis in cattleyak Sertoli cells by regulating specific signaling pathways

Infertility is a major reproductive problem in placental mammals, especially humans, affecting approximately 15% of families worldwide [1,2]. The most common causes of male sterility are aberrant spermatogenesis, spermatogenesis arrest or complete loss of spermatogonial germ cells. Cattleyak, an interspecific hybrid of cattle (Bos Taurus ♂) and yak (Bos grunniens ♀), exhibits markedly higher performance in milk and meat production than that of yak, while its adaptability to the Qinghai Tibet Plateau is equivalent to that of yak [3]. Thus, the breeding of cattleyak is an important way to improve the production efficiency of yak, which is beneficial for development of the economy in that region. Blocking spermatogenesis leads to infertility in male cattleyaks, which greatly restricts their breeding capability and the effective utilization of heterosis; moreover, many of the dominant genes cannot be stabilized and passed on to their offspring [4]. In recent decades, advances in molecular genetics have enabled scientists to identify several genes required for male reproduction, and some cases of infertility have been attributed to loss one or more of these genes' functions [5]. High-throughput sequencing technologies have also been successfully used to identify some genes associated with male cattleyak infertility [6,7], but it's still a tremendous challenge to uncover the mechanism of cattleyak male sterility.

As the only somatic cells in seminiferous tubules, Sertoli cells (SCs) play a vital role in regulating spermatogenesis and the fate of spermatogonial stem cells [8,9]. SCs provide nutritional, immunological, and structural support for developing germ cells [9], and a stable microenvironment for spermatogonial stem cells [10]. In addition, SCs participate in regulation of apoptosis and proliferation of spermatogonial germ cells by secreting necessary proteins and other factors [11], which regulate the production of sperm and maintain male fertility [12]. The number of immature SCs determines the total number of mature SCs, which decides the size of the testis, the competence of spermatogenesis, and the extent of sperm production [13]. The proliferation of SCs is controlled by several growth factors and hormones (such as follicle stimulating hormone, luteinizing hormone, testosterone, epidermal growth factor, and insulin‐like growth factor 1) [[13], [14], [15]]. Hence, to understand the role of SCs in male spermatogenesis is fundamental for exhaustive research on the mechanism of male reproduction and infertility.

An increasing body of evidence has revealed that small non-coding RNAs play an importance role in male reproduction and infertility [16,17]. MicroRNAs (miRNAs) are a class of 19–25 nucleotide-long RNAs essential for controlling the expression of specific genes via binding to 3′ untranslated regions (3′UTRs) of the mRNA, which leads to mRNA destabilization or degradation [18]. However, the functions of only a few miRNAs have been determined, and these only partially. The activities of most miRNAs are still unknown. The existing results reveal that various biological processes, such as cell differentiation, apoptosis, and proliferation in mammalian species, require regulation by miRNAs. Most miRNAs are highly conserved in species and have remarkable spatial and temporal patterns [[19], [20], [21]]. Currently, in the field of male infertility, new studies have revealed more miRNAs that are necessary for spermatogenesis and SC proliferation [18,22]. The expression of miRNAs in mouse testes at different periods was established by gene chip and miRscan, and the results showed that miRNAs can regulate the levels of hormones that affect male reproductive capacity [23,24]. Previous studies revealed that the expression of target genes in SCs was inhibited by miRNAs, thereby controlling their proliferation and apoptosis [14,25,26]. Dicer1 and Drosha are the key enzymes involved in the process of miRNA maturation, and mutations in these processing enzymes can lead to infertility or abnormal spermatogenesis [27,28]. Specific knockdown of these enzymes significantly decreases the expression of some key genes in SCs and can cause azoospermia or male infertility, such as from Sertoli cell-only syndrome (SCOS) [27,29,30]. Interestingly, Yao and coworkers have demonstrated that 174 miRNAs identified in testicular tissue were closely related to SCOS, and miR-133b significantly promoted SCs proliferation by suppressing the expression of GLI3 mRNA [26]. In a previous study, we showed by transcriptome analysis that some miRNAs, including miR-34b-5p, were differentially expressed in yak and cattleyak testes, which suggested its association with male infertility in cattleyak [4,31]. These observations demonstrated that non-coding miRNAs in SCs were crucial for germ cell differentiation and growth. Although the miRNA expression profile in cattleyak testis has been established, the molecular mechanism of miR-34b-5p in regulating cattleyak SCs has not been elucidated.

Protein phosphatase 1 regulatory subunit 11 (PPP1R11), a ubiquitously expressed regulatory subunit of the protein phosphatase 1 holoenzyme (locates on chromosome 6, CDS contains 324 bp which encode 107 amino acids), is essential in various physiological processes, especially those relating to reproduction such as spermatogenesis, oocyte maturation, embryonic development, uterine homeostasis, and metabolic regulation in humans and mice [32,33]. Bioinformatics analysis showed that PPP1R11 was a potential target of miR-34b-5p, and thus, we hypothesized that miR-34b-5p could regulate PPP1R11 expression and affect the function of cattleyak SCs. This study is the first to explore the effects of miR-34b-5p and PPP1R11 on the growth of cattleyak SCs, and is useful as a marker for understanding the molecular mechanism of male cattleyak sterility and to develop ways to solve the problem.

留言 (0)

沒有登入
gif