Deficiency of WTAP in islet beta cells results in beta cell failure and diabetes in mice

Emerging importance of m6A modification in liver cancer and its potential therapeutic role

Liver cancer refers to malignant tumors that form in the liver and is usually divided into several types, the most common of which is hepatocellular carcinoma (HCC), which originates in liver cells. Other rare types of liver cancer include intrahepatic cholangiocarcinoma (iCCA). m6A modification is a chemical modification of RNA that usually manifests as the addition of a methyl group to adenine in the RNA molecule to form N6-methyladenosine. This modification exerts a critical role in various biological processes by regulating the metabolism of RNA, affecting gene expression. Recent studies have shown that m6A modification is closely related to the occurrence and development of liver cancer, and m6A regulators can further participate in the pathogenesis of liver cancer by regulating the expression of key genes and the function of specific cells. In this review, we provided an overview of the latest advances in m6A modification in liver cancer research and explored in detail the specific functions of different m6A regulators. Meanwhile, we deeply analyzed the mechanisms and roles of m6A modification in liver cancer, aiming to provide novel insights and references for the search for potential therapeutic targets. Finally, we discussed the prospects and challenges of targeting m6A regulators in liver cancer therapy.

Liver ALKBH5 regulates glucose and lipid homeostasis independently through GCGR and mTORC1 signaling

Maintaining glucose and lipid homeostasis is crucial for health, with dysregulation leading to metabolic diseases such as type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated fatty liver disease (MAFLD). This study identifies alkylation repair homolog protein 5 (ALKBH5), an RNA N6-methyladenosine (m6A) demethylase, as a major regulator in metabolic disease. ALKBH5 is up-regulated in the liver during obesity and also phosphorylated by protein kinase A, causing its translocation to the cytosol. Hepatocyte-specific deletion of Alkbh5 reduces glucose and lipids by inhibiting the glucagon receptor (GCGR) and mammalian target of rapamycin complex 1 (mTORC1) signaling pathways. Targeted knockdown of hepatic Alkbh5 reverses T2DM and MAFLD in diabetic mice, highlighting its therapeutic potential. This study unveils a regulatory mechanism wherein ALKBH5 orchestrates glucose and lipid homeostasis by integrating the GCGR and mTORC1 pathways, providing insight into the regulation of metabolic diseases.

Exploring the methyl-verse: Dynamic interplay of epigenome and m6A epitranscriptome

The orchestration of dynamic epigenetic and epitranscriptomic modifications is pivotal for the fine-tuning of gene expression. However, these modifications are traditionally examined independently. Recent compelling studies have disclosed an interesting communication and interplay between m6A RNA methylation (m6A epitranscriptome) and epigenetic modifications, enabling the formation of feedback circuits and cooperative networks. Intriguingly, the interaction between m6A and DNA methylation machinery, coupled with the crosstalk between m6A RNA and histone modifications shape the transcriptional profile and translational efficiency. Moreover, m6A modifications interact also with non-coding RNAs, modulating their stability, abundance, and regulatory functions. In the light of these findings, m6A imprinting acts as a versatile checkpoint, linking epigenetic and epitranscriptomic layers toward a multilayer and time-dependent control of gene expression and cellular homeostasis. The scope of the present review is to decipher the m6A-coordinated circuits with DNA imprinting, chromatin architecture, and non-coding RNAs networks in normal physiology and carcinogenesis. Ultimately, we summarize the development of innovative CRISPR-dCas engineering platforms fused with m6A catalytic components (m6A writers or erasers) to achieve transcript-specific editing of m6A epitranscriptomes that can create new insights in modern RNA therapeutics.

N6-methyladenine RNA methylation epigenetic modification and diabetic microvascular complications

N6-methyladensine (m6A) has been identified as the best-characterized and the most abundant mRNA modification in eukaryotes. It can be dynamically regulated, removed, and recognized by its specific cellular components (respectively called "writers," "erasers," "readers") and have become a hot research field in a variety of biological processes and diseases. Currently, the underlying molecular mechanisms of m6A epigenetic modification in diabetes mellitus (DM) and diabetic microvascular complications have not been extensively clarified. In this review, we focus on the effects and possible mechanisms of m6A as possible potential biomarkers and therapeutic targets in the treatment of DM and diabetic microvascular complications.

Downregulation of Wtap causes dilated cardiomyopathy and heart failure

RNA binding proteins have been shown to regulate heart development and cardiac diseases. However, the detailed molecular mechanisms is not known. In this study, we identified Wilms' tumor 1-associating protein (WTAP, a key regulatory protein of the m6A RNA methyltransferase complex) as a key regulator of heart function and cardiac diseases. WTAP is associated with heart development, and its expression is downregulated in both human and mice with heart failure. Cardiomyocyte-specific knockout of Wtap (Wtap-CKO) induces dilated cardiomyopathy, heart failure and neonatal death. Although WTAP deficiency in the heart decreases METTL3 (methyltransferase-like 3) protein levels, cardiomyocyte-specific overexpression of Mettl3 in Wtap-CKO mice does not rescue the phenotypes of Wtap-CKO mice. Instead, WTAP deficiency in the heart decreases chromatin accessibility in the promoter regions of Mef2a (myocyte enhancer factor-2α) and Mef2c, leading to reduced mRNA and protein levels of these genes and lower expression of their target genes. Conversely, WTAP directly binds to the promoter of the Mef2c gene and increases its promoter luciferase activity and expression. These data demonstrate that WTAP plays a key role in heart development and cardiac function by maintaining the chromatin accessibility of cardiomyocyte specific genes.

Methyltransferase-like 3 modifications of RNAs: Implications for the pathology in the endocrine system

Methyltransferase-like 3 (METTL3) is the most well-known element of N6-methyladenosine modification on RNAs. METTL3 deposits a methyl group onto target RNAs to modify their expression, ultimately regulating various physiological and pathological events. Numerous studies have suggested the significant role of METTL3 in endocrine dysfunction and related disorders. However, reviews that summarize and interpret these studies are lacking. In this review, we systematically analyze such studies, including obesity, type 2 diabetes mellitus (T2DM), T2DM-induced diseases, pancreatic cancer, and thyroid carcinoma. This review indicates that METTL3 contributes remarkably to the endocrine dysfunction and progression of obesity, T2DM, T2DM-induced diseases, pancreatic cancer, and thyroid carcinoma. In conclusion, this review provides a comprehensive interpretation of the mechanism via which METTL3 functions on RNAs and regulates various endocrine dysfunction events and suggest potential associated correlations. Our review, thus, provides a valuable reference for further fundamental studies and clinical applications.

Emerging role of N6-methyladenosine in the homeostasis of glucose metabolism

N6-methyladenosine (m6A) is the most prevalent post-transcriptional internal RNA modification, which is involved in the regulation of diverse physiological processes. Dynamic and reversible m6A modification has been shown to regulate glucose metabolism, and dysregulation of m6A modification contributes to glucose metabolic disorders in multiple organs and tissues including the pancreas, liver, adipose tissue, skeletal muscle, kidney, blood vessels, and so forth. In this review, the role and molecular mechanism of m6A modification in the regulation of glucose metabolism were summarized, the potential therapeutic strategies that improve glucose metabolism by targeting m6A modifiers were outlined, and feasible directions of future research in this field were discussed as well, providing clues for translational research on combating metabolic diseases based on m6A modification in the future.

Insights into RNA N6-methyladenosine in Glucose and Lipid Metabolic Diseases and Their Therapeutic Strategies

The incidence of glucose and lipid metabolism diseases, including type 2 diabetes, obesity, metabolic syndrome, and nonalcoholic fatty liver disease, is rising, which places an enormous burden on people around the world. However, the mechanism behind these disorders remains incompletely understood. N6-methyladenosine (m6A) is 1 type of posttranscriptional RNA modification, and research has shown that it plays a crucial role in several metabolic diseases. m6A methylation is reversibly and dynamically regulated by methyltransferases (writers), demethylases (erasers), and m6A binding proteins (readers). Dysregulation of RNA m6A modification is related to different metabolic processes. Targeting RNA m6A methylation is a potential treatment strategy for these chronic metabolic diseases. This review discusses studies on RNA m6A modification in metabolic diseases and existing therapeutic drugs, with the aim of providing a concise perspective on its potential applications in managing metabolic disorders.

Hepatocyte-specific Wtap deficiency promotes hepatocellular carcinoma by activating GRB2-ERK depending on downregulation of proteasome-related genes

Wilm's tumor 1-associating protein (WTAP), a regulatory protein of the m6A methyltransferase complex, has been found to play a role in regulating various physiological and pathological processes. However, the in vivo role of WTAP in the pathogenesis of hepatocellular carcinoma (HCC) is unknown. In this study, we have elucidated the crucial role of WTAP in HCC progression and shown that hepatic deletion of Wtap promotes HCC pathogenesis through activation of multiple signaling pathways. A single dose of diethylnitrosamine injection causes more and larger HCCs in hepatocyte-specific Wtap knockout (Wtap-HKO) mice than Wtapflox/flox mice fed with either normal chow diet or a high-fat diet. Elevated CD36, IGFBP1 (insulin-like growth factor-binding protein 1), and chemokine (C-C motif) ligand 2 (CCL2) expression leads to steatosis and inflammation in the Wtap-HKO livers. The hepatocyte proliferation is dramatically increased in Wtap-HKO mice, which is due to higher activation of extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription-3 signaling pathways. Hepatic deletion of Wtap activates the ERK signaling pathway by increasing the protein stability of GRB2 and ERK1/2, which is due to the decreased expression of proteasome-related genes. Restoring PSMB4 or PSMB6 (two key components of the proteasome) leads to the downregulation of GRB2 and ERK1/2 in Wtap-HKO hepatocytes. Mechanistically, WTAP interacts with RNA polymerase II and H3K9ac to maintain expression of proteasome-related genes. These results demonstrate that hepatic deletion of Wtap promotes HCC progression through activating GRB2-ERK1/2-mediated signaling pathway depending on the downregulation of proteasome-related genes especially Psmb4 and Psmb6.

m6A epitranscriptomic modification in diabetic microvascular complications

N6-methyladenosine (m6A) modifications are modulated by m6A methyltransferases, m6A demethylases, and m6A-binding proteins. The dynamic and reversible patterns of m6A modification control cell fate programming by regulating RNA splicing, translation, and decay. Emerging evidence demonstrates that m6A modification of coding and noncoding RNAs exerts crucial effects that influence the pathogenesis of diabetic microvascular complications that include diabetic cardiomyopathy, diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and diabetic dermatosis. In this review, we summarize the roles of m6A modification and m6A modification-related enzymes in diabetic microvascular complications and discuss potential m6A modification-related enzyme-targeting therapeutic strategies.

METTL14 regulates microglia/macrophage polarization and NLRP3 inflammasome activation after ischemic stroke by the KAT3B-STING axis

N6-methyladenosine (m6A) plays a crucial role in ischemic stroke, whereas the role of methyltransferase-like 14 (METTL14) in ischemic stroke remains unknown. A model of middle cerebral artery occlusion (MCAO) in rats and oxygen-glucose deprivation/reperfusion (OGD/R) model in HAPI cells were used to simulate ischemic stroke in vivo and in vitro. We found that METTL14 level was upregulated in microglia/macrophage after MCAO and OGD/R. METTL14 enhanced the expression of KAT3B by promoting the m6A modification of KAT3B mRNA. STING has been identified as a target for KAT3B and KAT3B increased STING expression by enhancing H3K27ac in the STING promoter. METTL14 promoted M1 polarization and NLRP3 inflammasome/pyroptosis axis by the KAT3B-STING signaling after OGD/R. METTL14 depletion relieved brain injury by inhibiting M1-like microglia/macrophage polarization and NLRP3 inflammasome/pyroptosis axis in MCAO rats. These findings indicate that METTL14 depletion relieves MCAO-induced brain injury, probably via switching microglia/macrophage from M1 towards M2 and restraining NLRP3 inflammasome/pyroptosis axis in microglia/macrophage.

Downregulation of hepatic METTL3 contributes to APAP-induced liver injury in mice

Background & Aims

Acetaminophen (APAP) overdose is a major cause of acute liver failure in the Western world, but its molecular mechanisms are not fully understood. Methyltransferase-like 3 (METTL3) is a core N6-methyl-adenosine (m6A) RNA methyltransferase that has been shown to regulate many physiological and pathological processes. This study aimed to investigate the role of METTL3 in APAP-induced liver injury in mice.

Methods

Hepatocyte-specific Mettl3 knockout (Mettl3-HKO) mice and adenovirus-mediated gene overexpression or knockdown were used. We assayed APAP-induced liver injury by measuring serum alanine aminotransferase/aspartate aminotransferase activity, necrotic area, cell death, reactive oxygen species levels and activation of signalling pathways. We also performed mechanistic studies using a variety of assays and molecular techniques.

Results

Hepatic METTL3 is downregulated in APAP-induced liver injury, and hepatocyte-specific deletion of Mettl3 accelerates APAP-induced liver injury, leading to increased mortality as a result of the dramatic activation of the mitogen-activated protein kinase kinase 4 (MKK4) / c-Jun NH2-terminal kinase (JNK) signalling pathway. Inhibition of JNK by SP600125 largely blocks APAP-induced liver injury in Mettl3-HKO mice. Hepatic deletion of Mettl3 activates the MKK4/JNK signalling pathway by increasing the protein stability of MKK4 and JNK1/2 as a result of decreased proteasome activity. Restoration of proteasome activity by overexpression of proteasome 20S subunit beta 4 (PSMB4) or proteasome 20S subunit beta 6 (PSMB6) leads to the downregulation of MKK4 and JNK in Mettl3-HKO hepatocytes. Mechanistically, METTL3 interacts with RNA polymerase II and active histone modifications such as H3K9ac, H3K27ac, and H3K36me3 to maintain the expression of proteasome-related genes.

Conclusions

Our study demonstrated that downregulation of METTL3 promotes APAP-induced liver injury by decreasing proteasome activity and thereby enhancing activity of the MKK4/JNK signalling pathway.

Impact and Implications

Acetaminophen (APAP) overdose is a key cause of acute liver failure in the Western world, but its molecular mechanisms are not fully understood. We demonstrated in this study that methyltransferase-like 3 (METTL3), a core m⁶A RNA methyltransferase, is downregulated in APAP-induced liver injury, which exacerbates APAP-induced liver injury through enhancing the MKK4/JNK signalling pathway with involvement of the decreased proteasome activity.

N6-methyladenosine RNA modification: an emerging molecule in type 2 diabetes metabolism

Type 2 diabetes (T2D) is a metabolic disease with an increasing rate of incidence worldwide. Despite the considerable progress in the prevention and intervention, T2D and its complications cannot be reversed easily after diagnosis, thereby necessitating an in-depth investigation of the pathophysiology. In recent years, the role of epigenetics has been increasingly demonstrated in the disease, of which N6-methyladenosine (m6A) is one of the most common post-transcriptional modifications. Interestingly, patients with T2D show a low m6A abundance. Thus, a comprehensive analysis and understanding of this phenomenon would improve our understanding of the pathophysiology, as well as the search for new biomarkers and therapeutic approaches for T2D. In this review, we systematically introduced the metabolic roles of m6A modification in organs, the metabolic signaling pathways involved, and the effects of clinical drugs on T2D.

The role of m6A and m6Am RNA modifications in the pathogenesis of diabetes mellitus

The rapidly developing research field of epitranscriptomics has recently emerged into the spotlight of researchers due to its vast regulatory effects on gene expression and thereby cellular physiology and pathophysiology. N⁶-methyladenosine (m⁶A) and N⁶,2'-O-dimethyladenosine (m⁶Am) are among the most prevalent and well-characterized modified nucleosides in eukaryotic RNA. Both of these modifications are dynamically regulated by a complex set of epitranscriptomic regulators called writers, readers, and erasers. Altered levels of m⁶A and also several regulatory proteins were already associated with diabetic tissues. This review summarizes the current knowledge and gaps about m⁶A and m⁶Am modifications and their respective regulators in the pathophysiology of diabetes mellitus. It focuses mainly on the more prevalent type 2 diabetes mellitus (T2DM) and its treatment by metformin, the first-line antidiabetic agent. A better understanding of epitranscriptomic modifications in this highly prevalent disease deserves further investigation and might reveal clinically relevant discoveries in the future.

The Emerging, Multifaceted Role of WTAP in Cancer and Cancer Therapeutics

Cancer is a grave and persistent illness, with the rates of both its occurrence and death toll increasing at an alarming pace. N6-methyladenosine (m⁶A), the most prevalent mRNA modification in eukaryotic organisms, is catalyzed by methyltransferases and has a significant impact on various aspects of cancer progression. WT1-associated protein (WTAP) is a crucial component of the m⁶A methyltransferase complex, catalyzing m⁶A methylation on RNA. It has been demonstrated to participate in numerous cellular pathophysiological processes, including X chromosome inactivation, cell proliferation, cell cycle regulation, and alternative splicing. A better understanding of the role of WTAP in cancer may render it a reliable factor for early diagnosis and prognosis, as well as a key therapeutic target for cancer treatment. It has been found that WTAP is closely related to tumor cell cycle regulation, metabolic regulation, autophagy, tumor immunity, ferroptosis, epithelial mesenchymal transformation (EMT), and drug resistance. In this review, we will focus on the latest advances in the biological functions of WTAP in cancer, and explore the prospects of its application in clinical diagnosis and therapy.