In silico genome‐wide identification of m6A‐associated SNPs as potential functional variants for periodontitis

Inhibition of METTL3 Alleviates NLRP3 Inflammasome Activation via Increasing Ubiquitination of NEK7

N6-methyladenosine (m6A) modification, installed by METTL3-METTL14 complex, is abundant and critical in eukaryotic mRNA. However, its role in oral mucosal immunity remains ambiguous. Periodontitis is a special but prevalent infectious disease characterized as hyperinflammation of oral mucosa and bone resorption. Here, it is reported that genetic deletion of Mettl3 alleviates periodontal destruction via suppressing NLRP3 inflammasome activation. Mechanistically, the stability of TNFAIP3 (also known as A20) transcript is significantly attenuated upon m6A modification. When silencing METTL3, accumulated TNFAIP3 functioning as a ubiquitin-editing enzyme facilitates the ubiquitination of NEK7 [NIMA (never in mitosis gene a)-related kinase 7], and subsequently impairs NLRP3 inflammasome assembly. Furtherly, Coptisine chloride, a natural small-molecule, is discovered as a novel METTL3 inhibitor and performs therapeutic effect on periodontitis. The study unveils a previously unknown pathogenic mechanism of METTL3-mediated m6A modifications in periodontitis and indicates METTL3 as a potential therapeutic target.

Retinoic Acid Upregulates METTL14 Expression and the m6A Modification Level to Inhibit the Proliferation of Embryonic Palate Mesenchymal Cells in Cleft Palate Mice

Cleft palate only (CPO) is one of the most common craniofacial birth defects. Environmental factors can induce cleft palate by affecting epigenetic modifications such as DNA methylation, histone acetylation, and non-coding RNA. However, there are few reports focusing on the RNA modifications. In this study, all-trans retinoic acid (atRA) was used to simulate environmental factors to induce a C57BL/6J fetal mouse cleft palate model. Techniques such as dot blotting and immunofluorescence were used to find the changes in m6A modification when cleft palate occurs. RNA-seq and KEGG analysis were used to screen for significantly differentially expressed pathways downstream. Primary mouse embryonic palate mesenchymal (MEPM) cells were successfully isolated and used for in vitro experimental verification. We found that an increased m6A methylation level was correlated with suppressed cell proliferation in the palatine process mesenchyme of cleft palate mice. This change is due to the abnormally high expression of m6A methyltransferase METTL14. When using siRNAs and the m6A methyltransferase complex inhibitor SAH to interfere with the expression or function of METTL14, the teratogenic effect of atRA on primary cells was partially alleviated. In conclusion, METTL14 regulates palatal mesenchymal cell proliferation and cycle-related protein expression relies on m6A methylation modification, affecting the occurrence of cleft palate.

N6-methyladenosine-associated genetic variants in NECTIN2 and HPCAL1 are risk factors for abdominal aortic aneurysm

Although N6-methyladenosine (m6A) modification has been implicated in the pathogenesis of abdominal aortic aneurysm (AAA), the relationship between m6A-associated single nucleotide polymorphisms (m6A-SNPs) and AAA remains unknown. This study used integrative multi-omics analysis and clinical validation approaches to systematically identify potential m6A-SNPs connected with AAA risk. We found that rs6859 and rs10198139 could modulate the expression of local genes, NECTIN2 and HPCAL1, respectively, which exhibited upregulation in AAA tissues, and their risk variants were significantly correlated with an increased susceptibility to AAA. Incorporating rs6859 and rs10198139 improved the efficiency of AAA risk prediction compared to the model considering only conventional risk factors. Additionally, these two SNPs were predicted to be located within the regulatory sequences, and rs6859 showed a substantial impact on m6A modification levels. Our findings suggest that m6A-SNPs rs6859 and rs10198139 confer an elevated risk of AAA, possibly by promoting local gene expression through an m6A-mediated manner.

The essential roles of m6A modification in osteogenesis and common bone diseases

N6-methyladenosine (m6A) is the most prevalent modification in the eukaryotic transcriptome and has a wide range of functions in coding and noncoding RNAs. It affects the fate of the modified RNA, including its stability, splicing, and translation, and plays an important role in post-transcriptional regulation. Bones play a key role in supporting and protecting muscles and other organs, facilitating the movement of the organism, ensuring blood production, etc. Bone diseases such as osteoarthritis, osteoporosis, and bone tumors are serious public health problems. The processes of bone development and osteogenic differentiation require the precise regulation of gene expression through epigenetic mechanisms including histone, DNA, and RNA modifications. As a reversible dynamic epigenetic mark, m6A modifications affect nearly every important biological process, cellular component, and molecular function, including skeletal development and homeostasis. In recent years, studies have shown that m6A modification is involved in osteogenesis and bone-related diseases. In this review, we summarized the proteins involved in RNA m6A modification and the latest progress in elucidating the regulatory role of m6A modification in bone formation and stem cell directional differentiation. We also discussed the pathological roles and potential molecular mechanisms of m6A modification in bone-related diseases like osteoporosis and osteosarcoma and suggested potential areas for new strategies that could be used to prevent or treat bone defects and bone diseases.

METTL3 and METTL14 regulate IL-6 expression via RNA m6A modification of zinc transporter SLC39A9 and DNA methylation of IL-6 in periodontal ligament cells

The inflammatory response is a key process in periodontitis. The N6-methyladenosine (m6A) modification has been proven to be involved in various physiological and pathological processes. This study aims to investigate the role and downstream mechanism of N6-adenosine-enzyme subunits methyltransferase (METTL) 3 and 14 in the inflammatory response of periodontal ligament cells (PDLCs). The total m6A content and the expression of METTL3 and METTL14 were upregulated in lipopolysaccharide (LPS)-stimulated PDLCs. Knockdown of METTL3 or METTL14 suppressed the LPS-induced interleukin (IL)-6 expression, as shown by quantitative polymerase chain reaction (qPCR) and enzyme linked immunosorbent assay (ELISA). Mechanistically, conjoint analysis of m6A sequencing of METTL3-knockdown and METTL14-knockdown PDLCs revealed that the expression of solute carrier family 39 member 9 (SLC39A9) was mediated in a m6A-dependent manner. The suppression of LPS-induced IL-6 by METTL3 or METTL14 knockdown was partially counteracted by SLC39A9 knockdown, which induced downregulation of intracellular zinc via immunofluorescence staining. Amplicon bisulfite sequencing (AmpBS) demonstrated that METTL3/14 knockdown increased the methylation at one position of the IL-6 promoter, while SLC39A9 knockdown decreased it, which was basically consistent with the intracellular zinc concentration and negatively associated with IL-6 expression. Moreover, METTL3 or METTL14 knockdown attenuated the LPS-induced phosphorylation of p38 and JNK mitogen-activated protein kinase (MAPK), which was partially counteracted by SLC39A9 knockdown. These results revealed the "LPS-METTL3/14-SLC39A9-zinc-IL-6" axis and involvement of p38 and JNK MAPK signaling pathway in the inflammatory responses of PDLCs.

Genome-wide identification of m6A-associated single nucleotide polymorphisms in complex diseases of nervous system

N6-methyladenosine (m6A) is one of the most abundant chemical modifications on RNA and can affect the occurrence and development of diseases. Some studies have shown that the expressions of some m6A-related genes are significantly regulated by single nucleotide variants (SNV). However, the function of m6A-associated single nucleotide polymorphisms (m6A-SNP) remains unclear in multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD). Here, we identified the disease-associated m6A-SNPs by integrating genome-wide association study (GWAS) and m6A-SNPs from the RMVar database, and confirmed the relationship between these identified m6A-SNPs and their target genes in eQTL analysis and gene differential expression analysis. Finally, 26 genes corresponding to 20 m6A-SNPs with eQTL signals were identified and differentially expressed (P < 0.05) in MS, 15 genes corresponding to 12 m6A-SNPs (P < 1e-04) were differentially expressed in AD, and 27 PD-associated m6A-SNPs that regulated the expression of 31 genes were identified. There were 5 HLA genes with eQTL signals (HLA-DQB1, HLA-DRB1, HLA-DQA1, HLA-DQA2 and HLA-DQB1-AS1) to be detected in the three diseases. In summary, our study provided new insights into understanding the potential roles of these m6A-SNPs in disease pathogenesis as well as therapeutic target.

The Comprehensive Analysis of m6A-Associated Anoikis Genes in Low-Grade Gliomas

The relationship between N6-methyladenosine (m6A) regulators and anoikis and their effects on low-grade glioma (LGG) is not clear yet. The TCGA-LGG cohort, mRNAseq 325 dataset, and GSE16011 validation set were separately obtained via the Cancer Genome Atlas (TCGA), Chinese Glioma Genome Altas (CGGA), and Gene Expression Omnibus (GEO) databases. In total, 27 m6A-related genes (m6A-RGs) and 508 anoikis-related genes (ANRGs) were extracted from published articles individually. First, differentially expressed genes (DEGs) between LGG and normal samples were sifted out by differential expression analysis. DEGs were respectively intersected with m6A-RGs and ANRGs to acquire differentially expressed m6A-RGs (DE-m6A-RGs) and differentially expressed ANRGs (DE-ANRGs). A correlation analysis of DE-m6A-RGs and DE-ANRGs was performed to obtain DE-m6A-ANRGs. Next, univariate Cox and least absolute shrinkage and selection operator (LASSO) were performed on DE-m6A-ANRGs to sift out risk model genes, and a risk score was gained according to them. Then, gene set enrichment analysis (GSEA) was implemented based on risk model genes. After that, we constructed an independent prognostic model and performed immune infiltration analysis and drug sensitivity analysis. Finally, an mRNA-miRNA-lncRNA regulatory network was constructed. There were 6901 DEGs between LGG and normal samples. Six DE-m6A-RGs and 214 DE-ANRGs were gained through intersecting DEGs with m6A-RGs and ANRGs, respectively. A total of 149 DE-m6A-ANRGs were derived after correlation analysis. Four genes, namely ANXA5, KIF18A, BRCA1, and HOXA10, composed the risk model, and they were involved in apoptosis, fatty acid metabolism, and glycolysis. The age and risk scores were finally sifted out to construct an independent prognostic model. Activated CD4 T cells, gamma delta T cells, and natural killer T cells had the largest positive correlations with risk model genes, while activated B cells were significantly negatively correlated with KIF18A and BRCA1. AT.9283, EXEL.2280, Gilteritinib, and Pracinostat had the largest correlation (absolute value) with a risk score. Four risk model genes (mRNAs), 12 miRNAs, and 21 lncRNAs formed an mRNA-miRNA-lncRNA network, containing HOXA10-hsa-miR-129-5p-LINC00689 and KIF18A-hsa-miR-221-3p-DANCR. Through bioinformatics, we constructed a prognostic model of m6A-associated anoikis genes in LGG, providing new ideas for research related to the prognosis and treatment of LGG.

Genome-wide detection of m6A-associated SNPs in atrial fibrillation pathogenesis

Objective

N6-Methyladenosine (m6A) modification is of great importance in both the pathological conditions and physiological process. The m6A single nucleotide polymorphisms (SNPs) are associated with cardiovascular diseases including coronary artery disease, heart failure. However, it is unclear whether m6A-SNPs are involved in atrial fibrillation (AF). Here, we aimed to explore the relationship between m6A-SNPs and AF.

Method

The relationship between m6A-SNPs and AF was evaluated by analyzing the AF genome-wide association study (GWAS) and m6A-SNPs annotated by the m6AVar database. Further, eQTL and gene differential expression analysis were performed to confirm the association between these identified m6A-SNPs and their target genes in the development of AF. Moreover, we did the GO enrichment analysis to figure out the potential functions of these m6A-SNPs affected genes.

Result

Totally, 105 m6A-SNPs were identified to be significantly associated with AF (FDR < 0.05), among which 7 showed significant eQTL signals on local genes in the atrial appendage. By using four public AF gene expression datasets, we identified genes SYNE2, USP36, and THAP9 containing SNPs rs35648226, rs900349, and rs1047564 were differentially expressed in AF population. Further, SNPs rs35648226 and rs1047564 are potentially associated with AF by affecting m6A modification and both of them might have an interaction with RNA-binding protein, PABPC1.

Conclusion

In summary, we identified m6A-SNPs associated with AF. Our study provided new insights into AF development as well as AF therapeutic target.

Changes in N6-methyladenosine RNA methylomes of human periodontal ligament cells in response to inflammatory conditions

OBJECTIVE

To investigate the changes in the m6A methylation modification profile of human periodontal ligament cells (hPDLCs) in response to inflammatory conditions.

BACKGROUND

Periodontitis is an infectious disease of the periodontal support tissue that leads to the loss of alveolar bone. HPDLCs are primary cells that can repair periodontal tissue defects caused by periodontitis. However, the inflammatory conditions induce inflammatory damage and decrease ossification of hPDLCs. This inflammatory response depends on genetic and epigenetic mechanisms, including m6A methylation.

METHODS

HPDLCs were cultured with osteogenic induction medium (NC group), while TNF-α (10 ng/mL) and IL-1β (5 ng/mL) were added to simulate inflammatory conditions (Inflam group). Then RNA-seq and MeRIP-seq analyses were performed to identify m6A methylation modification in the transcriptome range of hPDLCs.

RESULTS

The results showed that the osteogenic differentiation of hPDLCs was inhibited under inflammatory conditions. RNA-seq analysis also revealed that the decreased genes in response to inflammatory conditions were primarily annotated in processes associated with ossification. Compared with the NC group, differentially m6A-methylated genes were primarily enriched in histone modification processes. Among 145 histone modification genes, 25 genes have been reported to be involved in the regulation of osteogenic differentiation, and they include KAT6B, EP300, BMI1, and KDMs (KDM1A, KDM2A, KDM3A, KDM4B, and KDM5A).

CONCLUSION

This study demonstrated that the m6A landscape of hPDLCs was changed in response to inflammation. M6A methylation differences among histone modification genes may act on the osteogenic differentiation of hPDLCs.

DNER and GNL2 are differentially m6A methylated in periodontitis in comparison with periodontal health revealed by m6A microarray of human gingival tissue and transcriptomic analysis

OBJECTIVE

This study aims to investigate the differences in the epigenomic patterns of N6-methyladenosine (m6A) methylation in gingival tissues between patients with periodontitis (PD) and healthy controls, identifying potential biomarkers.

BACKGROUND

As a multifactorial disease, PD involves multiple genetic and environmental effects. The m6A modification is the most prevalent internal mRNA modification and linked to various inflammatory diseases. However, the m6A modification pattern and m6A-related signatures in PD remain unclear.

MATERIALS AND METHODS

An m6A microarray of human gingival tissues was conducted in eight subjects: four diagnosed with PD and four healthy controls. Microarray analysis was performed to identify the differentially m6A methylated mRNAs (DMGs) and the differentially expressed mRNAs (DEGs). The differentially methylated and expressed mRNAs (DMEGs) were subjected to functional enrichment analysis by Metascape. The weighted gene co-expression network analysis (WGCNA) algorithm, the least absolute shrinkage and selection operator (LASSO) regression, and univariate logistic regression were performed to identify potential biomarkers. The cell type localization of the target genes was determined using single-cell RNA-seq (scRNA-seq) analysis. The m6A methylation level and gene expression of hub genes were subsequently verified by m6A methylated RNA immunoprecipitation (MeRIP) and quantitative real-time PCR (qRT-PCR).

RESULTS

In total, 458 DMGs, 750 DEGs, and 279 DMEGs were identified based on our microarray. Pathway analyses conducted for the DMEGs revealed that biological functions were mainly involved in the regulation of stem cell differentiation, ossification, circadian rhythm, and insulin secretion pathways. Besides, the genes involved in crucial biological processes were mainly expressed in fibroblast and epithelial cells. Furthermore, the m6A methylation and expression levels of two hub biomarkers (DNER and GNL2) were validated.

CONCLUSION

The current study exhibited a distinct m6A epitranscriptome, identified and verified two PD-related biomarkers (DNER and GNL2), which may provide novel insights into revealing the new molecular mechanisms and latent targets of PD.

Role of N6-adenosine-methyltransferase subunits METTL3 and METTL14 in the biological properties of periodontal ligament cells

The N6-methyladenosine (m6A) modification has been proven to be involved in various physiological and pathological processes. The m6A is catalyzed by methyltransferase complex, which mainly consist of methyltransferase (METTL) 3 and 14 heterodimer. The present study aimed to investigate the role of METTL 3 and 14 in biological properties of periodontal ligament cells (PDLCs) via RNA-sequencing and specific cell assays. Firstly, the expressions of METTL3 and METTL14 were observed in PDLCs. Then, RNA-sequencing showed that cell properties were influenced after METTL3 or METTL14 was knocked down via short hairpin RNA (shRNA). In sh-METTL3 or METTL14 PDLCs, cell counting kit 8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays showed a down-regulated proliferation, transwell system indicated suppressed migration. Lastly, alkaline phosphatase (ALP) and alizarin red staining (ARS) staining, quantitative polymerase chain reaction (qPCR) and western blot demonstrated the inhibited osteogenic potentials. It could be concluded that METTL3 and METTL14 play indispensable roles in the regenerative potential of PDLCs.

Impact of m6A demethylase (ALKBH5, FTO) genetic polymorphism and expression levels on the development of pulmonary tuberculosis

Objective

The m6A methylation was involved in the pathogenesis of pulmonary tuberculosis (PTB), and our study aimed to reveal the potential association of m6A demethylase (ALKBH5, FTO) genes variation, expression levels and PTB.

Methods

Eight SNPs (ALKBH5 gene rs8400, rs9913266, rs12936694, rs4925144 and FTO gene rs6499640, rs8047395, rs1121980, rs9939609) were selected for genotyping by SNPscan technique in 449 PTB patients and 463 healthy controls.

Results

The mRNA expression levels of ALKBH5, FTO were detected by qRT-PCR. There were no significant differences in genotype, allele distributions of all SNPs between PTB patients and healthy controls. Haplotype analysis demonstrated that the frequency of FTO gene GAAA haplotype was significantly reduced in PTB patients when compared to controls. ALKBH5 rs8400 AA genotype, A allele frequencies were associated with the decreased risk of sputum smear-positive, while AA genotype frequency was related to the increased risk of hypoproteinemia in PTB patients. In addition, rs9913266 variant was linked to the occurrence of drug-induced liver injury, sputum smear-positive, and rs4925144 variant was associated with leukopenia among PTB patients. In FTO gene, rs8047395 GG genotype and G allele frequencies were significantly higher in the PTB patients with drug resistance than that in the PTB patients without drug resistance. The ALKBH5, FTO expression levels were significantly decreased in PTB patients in comparison to controls. Moreover, ALKBH5 level was increased in PTB patients with drug resistance, and FTO level was decreased in PTB patients with sputum smear-positive.

Conclusion

FTO gene polymorphisms might be associated with PTB susceptibility, and ALKBH5, FTO levels were decreased in PTB patients, suggesting that these m6A demethylase played important roles in PTB.

FTO/RUNX2 signaling axis promotes cementoblast differentiation under normal and inflammatory condition

N⁶-methyladenosine (m⁶A) is the most prevalent mRNA modification which plays crucial roles in various biological processes, but its role in cementogenesis remains largely unknown. Here, using time-series transcriptomic analysis, we reveal that mRNA m⁶A demethylase Fat mass and obesity-associated protein (FTO) is involved in cementogenesis. Knocking down FTO decreases cementoblast differentiation and mineralization in both OCCM-30 cellular model and murine ectopic bone formation model. Mechanistically, we find that FTO directly binds Runt-related transcription factor 2 (Runx2) mRNA, an important cementogenesis factor, thus protecting it from YTH domain-containing family protein 2 (YTHDF2) mediated degradation, when cementoblasts are differentiating. Knocking down YTHDF2 restores the expression of Runx2 in FTO-knockdown cells. Moreover, under inflammatory conditions, TNF-α inhibits cementoblast differentiation and mineralization partly through FTO/RUNX2 axis. Collectively, our study reveals an important regulatory role of FTO/RUNX2 axis in normal and pathological cementogenesis.

In silico identification and in vitro expression analysis of breast cancer-related m6A-SNPs

Research on m6A-associated SNPs (m6A-SNPs) has emerged recently due to their possible critical roles in many key biological processes. In this sense, several investigations have identified m6A-SNPs in different diseases. In order to gain a more complete understanding of the role that m6A-SNPs can play in breast cancer, we performed an in silico analysis to identify the m6A-SNPs associated with breast cancer and to evaluate their possible effects. For this purpose, we downloaded SNPs related to breast cancer and a list of m6A-SNPs from public databases in order to identify which ones appear in both. Subsequently, we assessed the identified m6A-SNPs in silico by expression quantitative trait loci (eQTL) analysis and differential gene expression analysis. We genotyped the m6A-SNPs found in the in silico analysis in 35 patients with breast cancer, and we carried out a gene expression analysis experimentally on those that showed differences. Our results identified 981 m6A-SNPs related to breast cancer. Four m6A-SNPs showed an eQTL effect and only three were in genes that presented an altered gene expression. When the three m6A-SNPs were evaluated in the tissue sample of our breast cancer patients, only the m6A-SNP rs76563149 located in ZNF354A gene presented differences in allele frequencies and a low gene expression in breast cancer tissues, especially in luminal B HER2+ subtype. Future investigations of these m6A-SNPs should expand the study in different ethnic groups and increase the sample sizes to test their association with breast cancer and elucidate their molecular function.

N6-methyladenosine-related single-nucleotide polymorphism analyses identify oncogene RNFT2 in bladder cancer

Background

Single-nucleotide polymorphisms (SNPs) in N6-methyladenosine (m6A) related genetic locus play significant roles in tumorigenesis and development. The expression level of many oncogenes and tumour suppressor genes changed because of m6A-associated SNPs. In addition, the relationship between m6A-SNP and bladder cancer (BCa) has not been well studied.

Methods

We screened m6A-SNPs in BCa by combining m6A-SNPs data and GWAS-SNPs data. Expression quantitative trait loci (eQTL) and differential expression gene (DEGs) analyses were performed. In ring finger protein, transmembrane 2 (RNFT2), rs3088107 (C  > G) was found to have significant eQTL signals and make RNFT2 gene differentially-regulated mostly in BCa. We validated the expression level of RNFT2 in 32 pairs of BCa tissues and eight BCa cell lines by quantitative real-time PCR (qRT-PCR). Functional assays were performed to investigate the role of rs3088107 and RNFT2 in BCa in vitro.

Results

We identified 673 m6A-SNPs, which were associated with BCa. Of these m6A-SNPs, 221 showed eQTL signals, amongst which, rs3088107 in RNFT2 showed significant eQTL signals. Results of bioinformatic analyses showed that 11 genes with m6A-SNPs had a differential expression level in BCa. RNFT2 was predicted to be significantly up-regulated in BCa. The qRT-PCR results validated that RNFT2 was highly expressed in our own BCa tissues and cell lines. High expression of RNFT2 also indicated a worse overall survival. We also revealed that rs3088107 (C  > G) could inhibit the expression and m6A modification of RNFT2 by qRT-PCR, western-blot and m6A-RIP assays. Moreover, the results of functional assays indicated that RNFT2 promoted BCa cell proliferation and migration.

Conclusion

This research found that m6A-SNPs were associated with oncogene RNFT2 in BCa. Furthermore, m6A-SNPs showed great application potential as a new BCa diagnostic biomarker and prognostic indicator.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02701-z.

A genome-wide association analysis: m6A-SNP related to the onset of oral ulcers

Oral ulcers are one of the most common inflammatory diseases on oral mucosa that have obvious impacts on patients. Studies have shown that N6-methyladenosine (m6A) RNA transcription modification may be involved in the development of various inflammatory responses, and whether the pathogenesis of oral ulcers is related to m6A is unclear. This study aims to identify how m6A-related single nucleotide polymorphisms (m6A-SNPs) may affect oral ulcers. The UKBB dataset containing 10,599,054 SNPs was obtained from the GWAS database using the keyword "oral ulcer" and compared with the M6AVar database containing 13,703 m6A-SNPs.With 7,490 m6A-SNPs associated with oral ulcers identified, HaploReg and RegulomeDB were used for further functional validation and differential gene analysis was performed using the GEO database dataset GSE37265. A total of 7490 m6A-SNPs were detected in this study, 11 of which were related to oral ulcers (p<5E-08), and all of these SNPs showed eQTL signals. The SNP rs11266744 (p=2.00E-27) may regulate the expression of the local gene CCRL2, thereby participating in the pathogenesis of oral ulcers. In summary, by analyzing genome-wide association studies, this study showed that m6A modification may be involved in the pathogenesis of oral ulcers and CCRL2 may be the targeted gene.

METTL3-mediated m6A RNA methylation regulates dorsal lingual epithelium homeostasis

The dorsal lingual epithelium, which is composed of taste buds and keratinocytes differentiated from K14⁺ basal cells, discriminates taste compounds and maintains the epithelial barrier. N6-methyladenosine (m⁶A) is the most abundant mRNA modification in eukaryotic cells. How METTL3-mediated m⁶A modification regulates K14⁺ basal cell fate during dorsal lingual epithelium formation and regeneration remains unclear. Here we show knockout of Mettl3 in K14⁺ cells reduced the taste buds and enhanced keratinocytes. Deletion of Mettl3 led to increased basal cell proliferation and decreased cell division in taste buds. Conditional Mettl3 knock-in mice showed little impact on taste buds or keratinization, but displayed increased proliferation of cells around taste buds in a protective manner during post-irradiation recovery. Mechanically, we revealed that the most frequent m⁶A modifications were enriched in Hippo and Wnt signaling, and specific peaks were observed near the stop codons of Lats1 and FZD7. Our study elucidates that METTL3 is essential for taste bud formation and could promote the quantity recovery of taste bud after radiation.

Novel Associations Between METTL3 Gene Polymorphisms and Pediatric Acute Lymphoblastic Leukemia: A Five-Center Case-Control Study

Objective

To reveal the contributing role of METTL3 gene SNPs in pediatric ALL risk.

Patients and Methods

A total of 808 pediatric ALL cases and 1,340 cancer-free controls from five hospitals in South China were recruited. A case-control study by genotyping three SNPs in the METTL3 gene was conducted. Genomic DNA was abstracted from peripheral blood. Three SNPs (rs1263801 C>G, rs1139130 A>G, and rs1061027 A>C) in the METTL3 gene were chosen to be detected by taqman real-time polymerase chain reaction assay.

Results

That rs1263801 C>G, rs1139130 A>G, and rs1061027 A>C polymorphisms were significantly associated with increased pediatric ALL risk was identified. In stratification analyses, it was discovered that rs1263801 CC, rs1061027 AA, and rs1139130 GG carriers were more likely to develop ALL in subgroups of common B-ALL, MLL gene fusion. Rs1263801 CC and rs10610257 AA carriers were more possible to increase the risk of ALL in subgroups of low hyperdiploid, and all of these three SNPs exhibited a trend toward the risk of ALL. All of these three polymorphisms were associated with the primitive/naïve lymphocytes and MRD in marrow after chemotherapy in ALL children. Rs1263801 CC and rs1139130 AA alleles provided a protective effect on MRD ≥0.01% among CCCG-treated children. As for rs1139130, AA alleles provided a protective effect on MRD in marrow ≥0.01% on 33 days and 12 weeks among CCCG-treated children, but provided a risk effect on MRD in the marrow ≥0.01% among SCCLG-treated children. As for rs1263801 CC and rs1139130 AA, these two alleles provided a protective effect on MRD in the marrow ≥0.01% among CCCG-treated children.

Conclusion

In this study, we revealed that METTL3 gene polymorphisms were associated with increased pediatric ALL risk and indicated that METTL3 gene polymorphisms might be a potential biomarker for choosing ALL chemotherapeutics.

Genome-Wide Identification of m6A-Associated Single-Nucleotide Polymorphisms in Colorectal Cancer

Background

N6-methyladenosine (m6A)-associated single-nucleotide polymorphisms (SNPs) play important roles in cancers, with previous research suggesting potential associations between m6A-SNPs and cancer. However, the relationship between the genetic determinants of m6A modification and colorectal cancer (CRC) remains unclear.

Methods

An integrative method combining raw data and summary statistics of genome-wide association studies with expression quantitative trait loci (eQTL) and differential expression data was applied to screen potential candidate CRC-associated m6A-SNPs.

Results

A total of 402 m6A-SNPs were identified as being associated with CRC (p < 0.001), with 98 showing eQTL signals. In particular, three genes were found to harbor CRC-associated m6A-SNPs: rs178184 in NOVA1, rs35782901 in HTR4, and rs60571683 in SLCO1B3. These genes were differentially expressed in at least one publicly available dataset (p < 0.05), with NOVA1 (p = 3.41×10^-11) and HTR4 (p = 5.56×10^-7) being significantly downregulated in CRC (dataset: GSE89076), and SLCO1B3 was significantly overexpressed (datasets: GSE32323 [p = 3.27×10^-5], GSE21510 [p = 1.09×10^-6], and GSE89076 [p = 7.63×10^-6]).

Conclusion

This study identified three m6A-SNPs (rs178184, rs35782901, and rs60571683) that may be associated with CRC. However, the lack of analysis of primary CRC samples in order to further elucidate the underlying pathogenesis is a major limitation of this study. Future investigations are needed to validate these CRC-associated m6A-SNPs and explore the m6A-mediated pathogenic mechanism in CRC.

Integrative genomic analysis of N6-methyladenosine-single nucleotide polymorphisms (m6A-SNPs) associated with breast cancer

Due to the important role of N6-methyladenosine (m⁶A) in breast cancer, single nucleotide polymorphisms (SNPs) in genes with m⁶A modification may also be involved in breast cancer pathogenesis. In this study, we used a public genome-wide association study dataset to identify m⁶A-SNPs associated with breast cancer and to further explore their potential functions. We found 113 m⁶A-SNPs associated with breast cancer that reached the genome-wide suggestive threshold (5.0E-05), and 86 m⁶A-SNPs had eQTL signals. Only six genes were differentially expressed between controls and breast cancer cases in GEO datasets (GSE15852, GSE115144, and GSE109169), and the SNPs rs4829 and rs9610915 were located next to the m⁶A modification sites in the 3ʹUTRs of TOM1L1 and MAFF, respectively. In addition, we found that polyadenylate-binding protein cytoplasmic 1 might have a potential interaction with rs4829 (TOM1L1) and rs9610915 (MAFF). In summary, these findings indicated that the SNPs rs4829 and rs9610915 are potentially associated with breast cancer because they had eQTL signals, altered gene expression, and were located next to the m⁶A modification sites in the 3ʹUTRs of their coding genes. However, further studies are still needed to clarify how genetic variation affects the epigenetic modification, m⁶A, and its subsequent functions in the pathogenesis of breast cancer.

Comprehensive Analysis of Risk Factors for Periodontitis Focusing on the Saliva Microbiome and Polymorphism

Few studies have exhaustively assessed relationships among polymorphisms, the microbiome, and periodontitis. The objective of the present study was to assess associations simultaneously among polymorphisms, the microbiome, and periodontitis. We used propensity score matching with a 1:1 ratio to select subjects, and then 22 individuals (mean age ± standard deviation, 60.7 ± 9.9 years) were analyzed. After saliva collection, V3-4 regions of the 16S rRNA gene were sequenced to investigate microbiome composition, alpha diversity (Shannon index, Simpson index, Chao1, and abundance-based coverage estimator) and beta diversity using principal coordinate analysis (PCoA) based on weighted and unweighted UniFrac distances. A total of 51 single-nucleotide polymorphisms (SNPs) related to periodontitis were identified. The frequencies of SNPs were collected from Genome-Wide Association Study data. The PCoA of unweighted UniFrac distance showed a significant difference between periodontitis and control groups (p < 0.05). There were no significant differences in alpha diversity and PCoA of weighted UniFrac distance (p > 0.05). Two families (Lactobacillaceae and Desulfobulbaceae) and one species (Porphyromonas gingivalis) were observed only in the periodontitis group. No SNPs showed significant expression. These results suggest that periodontitis was related to the presence of P. gingivalis and the families Lactobacillaceae and Desulfobulbaceae but not SNPs.

The role of M6A modification in the regulation of tumor-related lncRNAs

N⁶-methyladenosine (m⁶A) is the most abundant modification in eukaryotic cells, and it regulates RNA transcription, processing, splicing, degradation, and translation. Long non-coding RNAs (lncRNAs), as transcriptional products with no or limited protein coding ability more than 200 nt in length, play an important role in epigenetic modification, mRNA transcription, splicing, stability, translation, and other biological functions. Extensive studies have shown that both m⁶A modification and lncRNAs are involved in the pathogenesis of various diseases, such as kinds of cancers, heart failure, Alzheimer’s disease, periodontitis, human abdominal aortic aneurysm, and obesity. To date, m⁶A modification has been identified as an important biological function in enrichment and regulation of lncRNAs. In this review, we summarize the role of m⁶A modification in the regulation and function of tumor-related lncRNAs. Moreover, we discuss the potential applications and possible future directions in the field.

Integrative Genomic Analysis Predicts Regulatory Role of N 6-Methyladenosine-Associated SNPs for Adiposity

Genome-wide association studies have identified many susceptible loci to explore the genetic factors of adiposity. However, the specific mechanisms by which these SNPs (single nucleotide polymorphism), particularly in the non-coding region, are involved in the pathogenesis of adiposity remain unclear. Recently, genetic variation is thought to affect N ⁶-methyladenosine (m6A) RNA modification, which is the most common post-transcriptional messenger RNA modification. In this study, we identified a large number of BMI (body mass index)-associated m6A-SNPs from published GWAS summary statistics through a public database and explored their potential mechanisms involved in the pathogenesis of adiposity. In summary, the integrative analysis detected 20,993 BMI-associated m6A-SNPs and 230 m6A-SNPs which reached the genome-wide suggestive threshold (5.0E-05), while 215 of them showed eQTL signals and 167 are the corresponding genes. The leading SNP rs8024 (C/A) was located next to the m6A modification site of 3'UTR of the IPO9 gene, which was predicted to affect the m6A modification site and regulate the expression of the IPO9 gene to participate in the pathogenesis of adiposity. This m6A-SNP/gene expression/adiposity triplets provide a new annotation for the pathogenic mechanism of adiposity risk loci identified by GWAS.

ALKBH5 gene polymorphisms and Wilms tumor risk in Chinese children: A five-center case-control study

BACKGROUND

Wilms tumor is a frequently diagnosed renal cancer among children with unclear genetic causes. N6-methyladenosine (m⁶ A) modification genes play critical roles in tumorigenesis. However, whether genetic variations of m⁶ A modification genes predispose to Wilms tumor remain unclear. ALKBH5 (AlkB homolog 5), a crucial member of m⁶ A modification genes, encodes a demethylase that functions to reverse m⁶ A RNA methylation.

METHODS

Herein, we evaluated the association of single nucleotide polymorphisms (SNPs) in the m⁶ A modification gene ALKBH5 and Wilms tumor susceptibility in a large multi-center case-control study. A total of 414 Wilms tumor cases and 1199 healthy controls were genotyped for ALKBH5 rs1378602 and rs8400 polymorphisms by TaqMan.

RESULTS

No significant association was detected between these two polymorphisms and Wilms tumor risk. Moreover, 1, 2, and 1-2 protective genotypes (rs1378602 AG/AA or rs8400 GG) did not significantly reduce Wilms tumor risk, compared with risk genotypes only. Stratification analysis revealed a significant relationship between rs1378602 AG/AA genotypes and decreased Wilms tumor risk in children in clinical stage I diseases [adjusted odds ratio (OR) = 0.56, 95% confidence interval (CI) = 0.32-0.98, P = .042]. The presence of 1-2 protective genotypes was correlated with decreased Wilms tumor risk in subgroups of age > 18 months, when compared to the absence of protective genotypes (adjusted OR = 0.74, 95% CI = 0.56-0.98, P = .035).

CONCLUSION

Collectively, our results demonstrate that ALKBH5 SNPs may exert a weak influence on susceptibility to Wilms tumor. This finding increases the understanding of the role of the m⁶ A gene in tumorigenesis of Wilms tumor.

Integration Analysis of m6A-SNPs and eQTLs Associated With Sepsis Reveals Platelet Degranulation and Staphylococcus aureus Infection are Mediated by m6A mRNA Methylation

Sepsis is a major threat with high mortality rate for critically ill patients. Response to pathogen infection by the host immune system is a key biological process involved in the onset and development of sepsis. Heterogeneous host genome variation, especially single nucleotide polymorphisms (SNPs), has long been suggested to contribute to differences in disease progression. However, the function of SNPs located in non-coding regions remains to be elucidated. Recently, m⁶A mRNA modification levels were revealed to differ at SNPs. As m⁶A is a crucial regulator of gene expression, these SNPs might control genes by changing the m⁶A level on mRNA. To investigate the potential role of m⁶A SNPs in sepsis, we integrated m⁶A-SNP and expression quantitative trait loci (eQTLs) data. Analysis revealed 15,720 m⁶A-cis-eQTLs and 381 m⁶A-trans-eQTLs associated with sepsis. We identified 1321 genes as locations of m⁶A-cis-eQTLs. These were enriched in platelet degranulation and Staphylococcus aureus infection pathways, which are vital for the pathophysiological process of sepsis. We conclude that m⁶A modification of mRNA plays a very important role in sepsis, with m⁶A-cis-eQTLs potentially having the most effect on individual variation in sepsis progression.