Mrhl Long Noncoding RNA Mediates Meiotic Commitment of Mouse Spermatogonial Cells by Regulating Sox8 Expression

Abstract

Long noncoding RNAs (lncRNAs) are important regulators of various biological processes, including spermatogenesis. Our previous studies have revealed the regulatory loop of mrhl RNA and Wnt signaling, where mrhl RNA negatively regulates Wnt signaling and gets downregulated upon Wnt signaling activation. This downregulation of mrhl RNA is important for the meiotic progression of spermatogonial cells. In our present study, we identified the transcription factor Sox8 as the regulatory link between mrhl RNA expression, Wnt signaling activation, and meiotic progression. In contrast to reports from other groups, we report the expression of Sox8 in germ cells and describe the molecular mechanism of Sox8 regulation by mrhl RNA during differentiation of spermatogonial cells. Binding of mrhl RNA to the Sox8 promoter is accompanied by the assembly of other regulatory factors involving Myc-Max-Mad transcription factors, corepressor Sin3a, and coactivator Pcaf. In the context of Wnt signaling, Sox8 directly regulates the expression of premeiotic and meiotic markers. Prolonged Wnt signaling activation in spermatogonial cells leads to changes in global chromatin architecture and a decrease in levels of stem cell markers.KEYWORDS Myc-Mad-Max, Sin3A, Sox8, Wnt signaling, mrhl RNA T he complexity of the eukaryotic genome has been attributed to its multifaceted regulatory networks. Over recent years, significant advancements in high-throughput analyses of the transcriptome have demonstrated the abundance of transcripts that do not code for proteins (noncoding RNAs [ncRNAs]). These ncRNAs are broadly classified as small and long noncoding RNAs. The small ncRNAs, such as microRNA (miRNA) and small interfering RNA (siRNA), play important roles in transcriptional and posttranscriptional gene regulation, while Piwi-associated RNAs (piRNAs) are involved in transposon regulation (1, 2). Another class is that of the long noncoding RNAs (lncRNAs), which are of various sizes between 200 bp and several kilobases (3). The role of lncRNAs in a plethora of functions, for example, dosage compensation (Xist and roX) (4, 5), genomic imprinting (Air and Kcnq1ot1) (6, 7), pluripotency (Evx1as and Hoxb5/6as) (8), cell differentiation and development (Fendrr, Bvht, Miat, Hotair, etc.) (9), nuclear architecture (NEAT1) (10), chromosome segregation (Concr) (11), immune response (lincRNA-EPS, EGOT) (12, 13), etc., have been characterized. lncRNAs bring about such copious functions by employment of diverse mechanisms such as translational inhibition (lincRNA-p21) (14), mRNA degradation (1/2-sbs RNAs) (15), RNA decoys (Gas5) (16)

Mettl3-mediated m6A regulates spermatogonial differentiation and meiosis initiation

“…DNA methylation and demethylation, histone modification, together with lncRNAs, microRNAs, piR-NA and many transcriptional factors have been shown to participate in regulating spermatogenic progression by modulating gene expression [42][43][44][45][46][47][48]. Alternative splicing is another important mechanism to regulate gene expression, and a recent report showed that Bcas2, an important alternative splicing factor, functions in spermatogonia and is involved in the transition to meiosis through regulating alternative mRNA splicing [49].…”

Regulation of long non-coding RNAs and circular RNAs in spermatogonial stem cells

“…Interestingly, Wnt signaling is suppressed in SSCs, but it is activated in differentiated spermatocytes (Yeh et al 2011). Mrhl decreases the expression level of Sox8, which is essential for spermatogonial differentiation (Kataruka et al 2017). It is speculated that Mrhl recruits corepressor Sin3A at the promoter site of Sox8 through a direct interaction.…”

Genome-wide identification and comparison of differentially expressed profiles of miRNAs and lncRNAs with associated ceRNA networks in the gonads of Chinese soft-shelled turtle, Pelodiscus sinensis

“…Knockouts of lncRNAs can cause a partial or complete loss of male fertility in Drosophila [25]. In mice, mrhl RNA can negatively regulate Wnt signalling and becomes down regulated upon the meiotic progression of spermatogonial cells [26,27]. In Daphnia magna, lncRNA Dapalr can transactivate and maintain dsx1 expression, which produces males in response to environmental stimuli [23].…”