Fat mass and obesity-associated factor (FTO)-mediated N6-methyladenosine regulates spermatogenesis in an age-dependent manner

The N6-methyladenosine landscape of ovarian development and aging highlights the regulation by RNA stability and chromatin state

The versatile epigenetic modification known as N6-methyladenosine (m6A) has been demonstrated to be pivotal in numerous physiological and pathological contexts. Nonetheless, the precise regulatory mechanisms linking m6A to histone modifications and the involvement of transposable elements (TEs) in ovarian development and aging are still not completely understood. First, we discovered that m6A modifications are highly expressed during ovarian aging (OA), with significant contributions from decreased m6A demethylase FTO and overexpressed m6A methyltransferase METTL16. Then, using FTO knockout mouse model and KGN cell line, we also observed that FTO deletion and METTL16 overexpression significantly increased m6A levels. This led to the downregulation of the methyltransferase SUV39H1, resulting in reduced H3K9me3 expression. The downregulation of SUV39H1 and H3K9me3 primarily activated LTR7 and LTR12, subsequently activating ERV1. This resulted in a decrease in cell proliferation, while the levels of apoptosis, cellular aging markers, and autophagy markers significantly increased in OA. In summary, our study offers intriguing insights into the role of m6A in regulating DNA epigenetics, including H3K9me3 and TEs, as well as autophagy, thereby accelerating OA.

Obesity and recurrent spontaneous abortion: the crucial role of weight management in pregnancy

Recurrent spontaneous abortion (RSA), characterized by the loss of two or more pregnancies, impacts approximately 1-2% of couples and poses a significant challenge for individuals of childbearing age. The precise mechanisms underlying RSA remain incompletely understood. Concurrently, the global prevalence of obesity is on the rise, with obesity being closely associated with female reproductive disorders and infertility. This study initially examines the pathways through which obesity contributes to RSA, encompassing factors such as embryonic euploid miscarriage, endometrial development, immune function, among others. Furthermore, adipokines and the fat mass and obesity-related (FTO) are identified as potential contributors to RSA. The study also explores the enhancement of pregnancy outcomes through various weight management strategies, with a particular focus on the roles of dietary interventions, physical activity, and weight control during pregnancy. Obesity is closely related to RSA in multiple aspects. Additional clinical prospective and experimental studies are required to explore its precise pathogenesis. Through this review, we aim to provide strategies for improvement and treatment approaches for RSA related to obesity. Through this review, we suggest potential clinical management strategies and research avenues aimed at offering enhancements and therapeutic insights for miscarriages linked to obesity and its associated risk factors.

N6-Methyladenosine Modification on the Function of Female Reproductive Development and Related Diseases

BACKGROUND

N6-methyladenosine (m6A) modification is a widespread and reversible epigenetic alteration in eukaryotic mRNA, playing a pivotal role in various biological functions. Its significance in female reproductive development and associated diseases has recently become a focal point of research.

OBJECTIVE

This review aims to consolidate current knowledge of the role of m6A modification in female reproductive tissues, emphasizing its regulatory dynamics, functional significance, and implications in reproductive health and disease.

METHODS

A comprehensive analysis of recent studies focusing on m6A modification in ovarian development, oocyte maturation, embryo development, and the pathogenesis of reproductive diseases.

RESULTS

m6A modification exhibits dynamic regulation in female reproductive tissues, influencing key developmental stages and processes. It plays critical roles in ovarian development, oocyte maturation, and embryo development, underpinning essential aspects of reproductive health. m6A modification is intricately involved in the pathogenesis of several reproductive diseases, including polycystic ovary syndrome (PCOS), premature ovarian failure (POF), and endometriosis, offering insights into potential molecular mechanisms and therapeutic targets.

CONCLUSION

The review highlights the crucial role of m6A modification in female reproductive development and related diseases. It underscores the need for further research to explore innovative diagnostic and therapeutic strategies for reproductive disorders, leveraging the insights gained from understanding m6A modification's impact on reproductive health.

Sperm RNA code in spermatogenesis and male infertility

Spermatozoa are traditionally thought to be transcriptionally inert, but recent studies have revealed the presence of sperm RNA, some of which is derived from the residues of spermatocyte transcription and some from epididymosomes. Paternal sperm RNA can be affected by external factors and further modified at the post-transcriptional level, for example N6-methyladenosine (m6A), thus shaping spermatogenesis and reproductive outcome. This review briefly introduces the origin of sperm RNA and, on this basis, summarizes the current knowledge on RNA modifications and their functional role in spermatogenesis and male infertility. The bottlenecks and knowledge gaps in the current research on RNA modification in male reproduction have also been indicated. Further investigations are needed to elucidate the functional consequences of these modifications, providing new therapeutic and preventive strategies for reproductive health and genetic inheritance.

RNA modifications: emerging players in the regulation of reproduction and development

The intricate world of RNA modifications, collectively termed the epitranscriptome, covers over 170 identified modifications and impacts RNA metabolism and, consequently, almost all biological processes. In this review, we focus on the regulatory roles and biological functions of a panel of dominant RNA modifications (including m 6A, m 5C, Ψ, ac 4C, m 1A, and m 7G) on three RNA types-mRNA, tRNA, and rRNA-in mammalian development, particularly in the context of reproduction as well as embryonic development. We discuss in detail how those modifications, along with their regulatory proteins, affect RNA processing, structure, localization, stability, and translation efficiency. We also highlight the associations among dysfunctions in RNA modification-related proteins, abnormal modification deposition and various diseases, emphasizing the roles of RNA modifications in critical developmental processes such as stem cell self-renewal and cell fate transition. Elucidating the molecular mechanisms by which RNA modifications influence diverse developmental processes holds promise for developing innovative strategies to manage developmental disorders. Finally, we outline several unexplored areas in the field of RNA modification that warrant further investigation.

RNA reading protein YTHDF2 mediates Benzo(k)fluoranthene induced male reproductive injury by regulating the stability of BCL2

Benzo (k) fluoranthene (BkF) has adverse effects on male reproduction, but its specific mechanism of action is still unclear. This study focused on the role of RNA reading protein YTHDF2 and its mechanism in BkF induced male reproductive injury. Mouse GC-2 spermatocytes were exposed to 0, 40, 80, 160 μM BkF. It was found that BkF significantly increased the apoptosis of GC-2 cell and decreased its survival rate. BCL2 in spermatocytes decreased significantly, while the expression of P53 and BAX exhibited a notable increase. Interestingly, the expression of RNA reading protein YTHDF2 progressively rose in tandem with the escalating BkF exposure dosage. Overexpression of YTHDF2 significantly reduced the viability of cells and increased the apoptosis rate. Meanwhile, there was a substantial increase in the expression of P53 and BAX, BCL2 was significantly down-regulated. On the contrary, interfering with YTHDF2 increased cell proliferation and reduced cell apoptosis. Furthermore, YTHDF2 overexpression exacerbated the decrease in cell viability under BkF exposure, while YTHDF2 knockdown was the opposite. The results from the RIP assay demonstrated a significant enhancement in the interaction of YTHDF2 protein with BCL2 mRNA following the overexpression of YTHDF2. In addition, animal experiments showed that there was an increase in apoptosis and a decrease in proliferation of testicular cells in mice in the high-dose (30 mg/kg) BkF group by TUNEL staining and Ki67 staining. Immunohistochemical analysis showed that BCL2 levels were significantly lower in the high-dose group than in the control group, while YTHDF2, P53 and BAX were dramatically increased. In summary, our study suggests that YTHDF2 has been implicated in BkF-induced male reproductive injury by promoting the degradation of BCL2.

Roles of N6-methyladenosine writers, readers and erasers in the mammalian germline

N6-methyladenosine (m6A) is the most abundant internal modification of mRNAs in eukaryotes. Numerous studies have shown that m6A plays key roles in many biological and pathophysiological processes, including fertility. The factors involved in m6A-dependent mRNA regulation include writers, which deposit the m6A mark, erasers, which remove it, and readers, which bind to m6A-modified transcripts and mediate the regulation of mRNA fate. Many of these proteins are highly expressed in the germ cells of mammals, and some have been linked to fertility disorders in human patients. In this review, we summarise recent findings on the important roles played by proteins involved in m6A biology in mammalian gametogenesis and fertility. Continued study of the m6A pathway in the mammalian germline will shed further light on the importance of epitranscriptomics in reproduction and may lead to effective treatment of human fertility disorders.

[The Roles of N6-Methyladenosine Modification and Its Regulators in Male Reproduction]

Infertility affects an estimated 10 to 15 percent of couples worldwide, with approximately half of the cases attributed to male-related issues. Most men diagnosed with infertility exhibit symptoms such as oligospermia, asthenospermia, azoospermia, and compromised sperm quality. Spermatogenesis is a complex and tightly coordinated process of germ cell differentiation, precisely regulated at transcriptional, posttranscriptional, and translational levels to ensure stage-specific gene expression during the development of spermatogenic cells and normal spermiogenesis. N6-methyladenosine (m6A) stands out as the most prevalent modification on eukaryotic mRNA, playing pivotal roles in various biological processes, including mRNA splicing, transportation, and translation. RNA methylation modification is a dynamic and reversible process primarily mediated by "writers", removed by "erasers", and recognized by "readers". In mammals, the aberrant methylation modification of m6A on mRNA is associated with a variety of diseases, including male infertility. However, the precise involvement of disrupted m6A modification in the pathogenesis of human male infertility remains unresolved. Intriguingly, a significant correlation has been found between the expression levels of m6A regulators in the testis and the severity of sperm concentration, motility, and morphology. Aberrant expression patterns of m6A regulatory proteins have been detected in anomalous human semen samples, including those of oligospermia, asthenozoospermia, and azoospermia. Furthermore, the examination of both sperm samples and testicular tissues revealed abnormal mRNA m6A modification, leading to reduced sperm motility and concentration in infertile men. Consequently, it is hypothesized that dysregulation of m6A modification might serve as an integral link in the mechanism of male infertility. This paper presents a comprehensive review of the recent discoveries regarding the spatial and temporal expression dynamics of m6A regulators in testicular tissues and the correlation between deregulated m6A regulators and human male infertility. Previous studies predominantly utilized constitutive or conditional knockout animal models for testicular phenotypic investigations. However, gene suppression in additional tissues could potentially influence the testis in constitutive knockout models. Furthermore, considering the compromised spermatogenesis observed in constitutive animals, distinguishing between the indirect effects of gene depletion on testicular development and its direct impact on the spermatogenic process is challenging, due to their intricate relationship. Such confounding factors might compromise the validity of the findings. To address this challenge, an inducible and conditional gene knockout model may serve as a superior approach. To date, nearly all reported studies have concentrated solely on the level changes of m6A and its regulators in germs cells, while the understanding of the function of m6A modification in testicular somatic cells remains limited. Testicular somatic cells, including peritubular myoid cells, Sertoli cells, and Leydig cells, play indispensable roles during spermatogenesis. Hence, comprehensive exploration of m6A modification within these cells as an additional crucial regulatory mechanism is warranted. In addition, exploration into the presence of unique methylation mechanisms or m6A regulatory factors within the testes is warranted. To elucidate the role of m6A modification in germ cells and testicular somatic cells, detailed experimental strategies need to be implemented. Among them, manipulation of the levels of key enzymes involved in m6A methylation and demethylation might be the most effective approach. Moreover, comprehensive analysis of the gene expression profiles involved in various signaling pathways, such as Wnt/β-catenin, Ras/MAPK, and Hippo, in m6A-modified germ cells and testicular somatic cells can provide more insight into its regulatory role in the spermatogenesis process. Further research in this area could provide valuable insights for developing innovative strategies to treat male infertility. Finally, considering the mitigation impact of m6A imbalance regulation on disease, investigation concerning whether restoring the equilibrium of m6A modification regulation can restore normal spermatogenesis function is essential, potentially elucidating the pivotal clinical significance of m6A modulation in male infertility.

The role of the m6A/m demethylase FTO in memory is both task and sex-dependent in mice

Formation of long-term memories requires learning-induced changes in both transcription and translation. Epitranscriptomic modifications of RNA recently emerged as critical regulators of RNA dynamics, whereby adenosine methylation (m6A) regulates translation, mRNA stability, mRNA localization, and memory formation. Prior work demonstrated a pro-memory phenotype of m6A, as loss of m6A impairs and loss of the m6A/m demethylase FTO improves memory formation. Critically, these experiments focused exclusively on aversive memory tasks and were only performed in male mice. Here we show that the task type and sex of the animal alter effects of m6A on memory, whereby FTO-depletion impaired object location memory in male mice, in contrast to the previously reported beneficial effects of FTO depletion on aversive memory. Additionally, we show that female mice have no change in performance after FTO depletion, demonstrating that sex of the mouse is a critical variable for understanding how m6A contributes to memory formation. Our study provides the first evidence for FTO regulation of non-aversive spatial memory and sexspecific effects of m6A, suggesting that identification of differentially methylated targets in each sex and task will be critical for understanding how epitranscriptomic modifications regulate memory.

FTO demethylates regulates cell-cycle progression by controlling CCND1 expression in luteinizing goat granulosa cells

In mammals, N6-methyladenosine (m6A) stands out as one of the most abundant internal mRNA modifications and plays a crucial role in follicular development. Nonetheless, the precise mechanism by which the demethylase FTO regulates the progression of the goat luteinizing granulosa cells (LGCs) cycle remains to be elucidated. In our study, we primarily assessed the protein and mRNA expression levels of genes using Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), cell proliferation via EdU, cell viability with CCK-8, and apoptosis and cell cycle progression through flow cytometry. Here, the results demonstrated that knockdown of FTO significantly enhanced apoptosis, impeded cell proliferation, and increased autophagy levels in goat LGCs. Furthermore, the silencing of FTO substantially reduced cyclin D1 (CCND1) expression through the recognition and degradation of YTHDF2, consequently prolonging the cell cycle progression. This study sheds light on the mechanism by which FTO demethylation governs cell cycle progression by controlling the expression of CCND1 in goat LGCs, underscoring the dynamic role of m6A modification in the regulation of cell cycle progression.