MORC3, a novel MIWI2 association partner, as an epigenetic regulator of piRNA dependent transposon silencing in male germ cells

The functions and mechanisms of piRNAs in mediating mammalian spermatogenesis and their applications in reproductive medicine

As the most abundant small RNAs, piwi-interacting RNAs (piRNAs) have been identified as a new class of non-coding RNAs with 24-32 nucleotides in length, and they are expressed at high levels in male germ cells. PiRNAs have been implicated in the regulation of several biological processes, including cell differentiation, development, and male reproduction. In this review, we focused on the functions and molecular mechanisms of piRNAs in controlling spermatogenesis, including genome stability, regulation of gene expression, and male germ cell development. The piRNA pathways include two major pathways, namely the pre-pachytene piRNA pathway and the pachytene piRNA pathway. In the pre-pachytene stage, piRNAs are involved in chromosome remodeling and gene expression regulation to maintain genome stability by inhibiting transposon activity. In the pachytene stage, piRNAs mediate the development of male germ cells via regulating gene expression by binding to mRNA and RNA cleavage. We further discussed the correlations between the abnormalities of piRNAs and male infertility and the prospective of piRNAs' applications in reproductive medicine and future studies. This review provides novel insights into mechanisms underlying mammalian spermatogenesis and offers new targets for diagnosing and treating male infertility.

The deubiquitinase cofactor UAF1 interacts with USP1 and plays an essential role in spermiogenesis

Spermiogenesis defines the final phase of male germ cell differentiation. While multiple deubiquitinating enzymes have been linked to spermiogenesis, the impacts of deubiquitination on spermiogenesis remain poorly characterized. Here, we investigated the function of UAF1 in mouse spermiogenesis. We selectively deleted Uaf1 in premeiotic germ cells using the Stra8-Cre knock-in mouse strain (Uaf1 sKO), and found that Uaf1 is essential for spermiogenesis and male fertility. Further, UAF1 interacts and colocalizes with USP1 in the testes. Conditional knockout of Uaf1 in testes results in disturbed protein levels and localization of USP1, suggesting that UAF1 regulates spermiogenesis through the function of the deubiquitinating enzyme USP1. Using tandem mass tag-based proteomics, we identified that conditional knockout of Uaf1 in the testes results in reduced levels of proteins that are essential for spermiogenesis. Thus, we conclude that the UAF1/USP1 deubiquitinase complex is essential for normal spermiogenesis by regulating the levels of spermiogenesis-related proteins.

Critical appraisal of the piRNA-PIWI axis in cancer and cancer stem cells

Small noncoding RNAs play an important role in various disease states, including cancer. PIWI proteins, a subfamily of Argonaute proteins, and PIWI-interacting RNAs (piRNAs) were originally described as germline-specific molecules that inhibit the deleterious activity of transposable elements. However, several studies have suggested a role for the piRNA-PIWI axis in somatic cells, including somatic stem cells. Dysregulated expression of piRNAs and PIWI proteins in human tumors implies that, analogously to their roles in undifferentiated cells under physiological conditions, these molecules may be important for cancer stem cells and thus contribute to cancer progression. We provide an overview of piRNA biogenesis and critically review the evidence for the role of piRNA-PIWI axis in cancer stem cells. In addition, we examine the potential of piRNAs and PIWI proteins to become biomarkers in cancer.

Analysis of circRNA-miRNA-mRNA regulatory network of embryonic gonadal development in Mulard duck

The aim of the study was to explore the regulatory mechanism of differences in embryonic gonadal development between intergeneric distance hybrid offspring Mulard ducks and parent ducks. The morphological differences gonadal tissues of Muscovy ducks, Pekin ducks and Mulard ducks at 12.5-day embryonic age were observed by sectioning and hematoxylin-eosin (HE) staining. Then followed by transcriptome sequencing to screen for gonadal development-related differentially expressed circRNAs and mRNAs to construct a competitive endogenous RNA (ceRNA) regulatory network. Finally, qRT-PCR and luciferase reporter system were used to verify the sequencing data and targeting relationship of ceRNA pairs. The results showed that the seminiferous tubule lumen of Mulard ducks was not obvious, while there were obvious seminiferous tubules and tubular structures in testis of Pekin ducks and Muscovy ducks, with number and shape indicating maturity. There were 18 upregulated circRNAs and 16 downregulated circRNAs in Mulard ducks and Pekin ducks, respectively, and 39 upregulated circRNAs and 1 downregulated circRNA in Mulard ducks and Muscovy ducks, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis found that genes involves in dorso-ventral axis formation, for example, neurogenic locus notch homolog protein 1 (NOTCH1), were significantly enriched (P < 0.05). The novel_circ_0002265-gga-miR-122-5p-PAFAH1B2 regulatory network was constructed. The qRT-PCR results showed that the sequencing results were reliable. The dual-luciferase reporter assay showed that gga-miR-122-5p exists binding site of circ_0002265 and PAFAH1B2, indicating circ_0002265-gga-miR-122-5p-PAFAH1B2 targeting relationship. In summary, the embryonic gonadal development of intergeneric hybrid Mulard ducks may be regulated by differentially expressed circRNAs and genes, such as novel_circ_0000519, novel_circ_0003537, NOTCH1, FGFR2, PAFAH1B1, and PAFAH1B2, among which circ_0002265-gga-miR-122-5p-PAFAH1B2 may participate in the targeted regulation of gonadal development in Mulard ducks. The findings of this study are helpful for analyzing the mechanism of embryonic gonadal development differences in avians.

ADAD2 functions in spermiogenesis and piRNA biogenesis in mice

BACKGROUND

Adenosine deaminase domain containing 2 (ADAD2) is a testis-specific protein composed of a double-stranded RNA binding domain and a non-catalytic adenosine deaminase domain. A recent study showed that ADAD2 is indispensable for the male reproduction in mice. However, the detailed functions of ADAD2 remain elusive.

OBJECTIVES

This study aimed to investigate the cause of male sterility in Adad2 mutant mice and to understand the molecular functions of ADAD2.

MATERIALS AND METHODS

Adad2 homozygous mutant mouse lines, Adad2-/- and Adad2Δ/Δ , were generated by CRISPR/Cas9. Western blotting and immunohistochemistry were used to reveal the expression and subcellular localization of ADAD2. Co-immunoprecipitation tandem mass spectrometry was employed to determine the ADAD2-interacting proteins in mouse testes. RNA-sequencing analyses were carried out to analyze the transcriptome and PIWI-interacting RNA (piRNA) populations in wildtype and Adad2 mutant testes.

RESULTS

Adad2-/- and Adad2Δ/Δ mice exhibit male-specific sterility because of abnormal spermiogenesis. ADAD2 interacts with multiple RNA-binding proteins involved in piRNA biogenesis, including MILI, MIWI, RNF17, and YTHDC2. ADAD2 co-localizes and forms novel granules with RNF17 in spermatocytes. Ablation of ADAD2 impairs the formation of RNF17 granules, decreases the number of cluster-derived pachytene piRNAs, and increases expression of ping-pong-derived piRNAs.

DISCUSSION AND CONCLUSION

In collaboration with RNF17 and other RNA-binding proteins in spermatocytes, ADAD2 directly or indirectly functions in piRNA biogenesis.

The TGF-β/SMAD Signaling Pathway Prevents Follicular Atresia by Upregulating MORC2

In mammals, female fertility is determined by the outcome of follicular development (ovulation or atresia). The TGF-β/SMAD signaling pathway is an important regulator of this outcome. However, the molecular mechanism by which the TGF-β/SMAD signaling pathway regulates porcine follicular atresia has not been fully elucidated. Microrchidia family CW-type zinc finger 2 (MORC2) is anovel epigenetic regulatory protein widely expressed in plants, nematodes, and mammals. Our previous studies showed that MORC2 is a potential downstream target gene of the TGF-β/SMAD signaling pathway. However, the role of MORC2 in porcine follicular atresia is unknown. To investigate this, qRT-PCR, western blotting, and TdT-mediated dUTP nick-end labeling were performed. Additionally, the luciferase activity assay was conductedto confirm that the TGF-β/SMAD signaling pathway regulates MORC2. Our results demonstrate that MORC2 is animportant anti-apoptotic molecule that prevents porcine follicular atresia via a pathway involving mitochondrial apoptosis, not DNA repair. Notably, this studyrevealsthat the TGF-β/SMAD signaling pathway inhibits porcine granulosa cell apoptosis by up-regulating MORC2. The transcription factor SMAD4 regulated the expression of MORC2 by binding to its promoter. Our results will help to reveal the mechanism underlying porcine follicular atresia and improve the reproductive efficiency of sows.

Structural and Functional Attributes of Microrchidia Family of Chromatin Remodelers

Chromatin remodelers affect the spatio-temporal dynamics of global gene-expression by structurally modulating and/or reorganizing the chromatin. Microrchidia (MORC) family is a relatively new addition to the four well studied families of chromatin remodeling proteins. In this review, we discuss the current understanding of the structural aspects of human MORCs as well as their epigenetic functions. From a molecular and systems-level perspective, we explore their participation in phase-separated structures, possible influence on various biological processes through protein-protein interactions, and potential extra-nuclear roles. We describe how dysregulation/dysfunction of MORCs can lead to various pathological conditions. We conclude by emphasizing the importance of undertaking integrated efforts to obtain a holistic understanding of the various biological roles of MORCs.