DNA Methylation Levels of the TBX5 Gene Promoter Are Associated with Congenital Septal Defects in Mexican Paediatric Patients

The TBX5 gene regulates morphological changes during heart development, and it has been associated with epigenetic abnormalities observed in congenital heart defects (CHD). The aim of this research was to evaluate the association between DNA methylation levels of the TBX5 gene promoter and congenital septal defects. DNA methylation levels of six CpG sites in the TBX5 gene promoter were evaluated using pyrosequencing analysis in 35 patients with congenital septal defects and 48 controls. Average methylation levels were higher in individuals with congenital septal defects than in the controls (p < 0.004). In five CpG sites, we also found higher methylation levels in patients than in the controls (p < 0.05). High methylation levels were associated with congenital septal defects (OR = 3.91; 95% CI = 1.02–14.8; p = 0.045). The analysis of Receiver Operating Characteristic (ROC) showed that the methylation levels of the TBX5 gene could be used as a risk marker for congenital septal defects (AUC = 0.68, 95% CI = 0.56–0.80; p = 0.004). Finally, an analysis of environmental factors indicated that maternal infections increased the risk (OR = 2.90; 95% CI = 1.01–8.33; p = 0.048) of congenital septal defects. Our data suggest that a high DNA methylation of the TBX5 gene could be associated with congenital septal defects.

The concurrence of DNA methylation and demethylation is associated with transcription regulation

The mammalian DNA methylome is formed by two antagonizing processes, methylation by DNA methyltransferases (DNMT) and demethylation by ten-eleven translocation (TET) dioxygenases. Although the dynamics of either methylation or demethylation have been intensively studied in the past decade, the direct effects of their interaction on gene expression remain elusive. Here, we quantify the concurrence of DNA methylation and demethylation by the percentage of unmethylated CpGs within a partially methylated read from bisulfite sequencing. After verifying ‘methylation concurrence’ by its strong association with the co-localization of DNMT and TET enzymes, we observe that methylation concurrence is strongly correlated with gene expression. Notably, elevated methylation concurrence in tumors is associated with the repression of 40~60% of tumor suppressor genes, which cannot be explained by promoter hypermethylation alone. Furthermore, methylation concurrence can be used to stratify large undermethylated regions with negligible differences in average methylation into two subgroups with distinct chromatin accessibility and gene regulation patterns. Together, methylation concurrence represents a unique methylation metric important for transcription regulation and is distinct from conventional metrics, such as average methylation and methylation variation.

Transcriptome and DNA Methylome Reveal Insights Into Phytoplasma Infection Responses in Mulberry (Morus multicaulis Perr.)

To reveal whether the response of mulberry to phytoplasma infection is associated with genome-wide DNA methylation changes, the methylome and transcriptome patterns of mulberry in response to phytoplasma infection were explored. Though the average methylation level of the infected leaves showed no significant difference from that of healthy leaves, there were 1,253 differentially methylated genes (DMGs) and 1,168 differentially expressed genes (DEGs) in the infected leaves, and 51 genes were found simultaneously to be differently methylated and expressed. It was found that the expression of G-type lectin S-receptor-like serine/threonine protein kinase gene (Mu-GsSRK) was increased, but its methylation level was decreased in the pathogen-infected or salicylic acid (SA)-treated leaves. Overexpression of Mu-GsSRK in Arabidopsis and in the hairy roots of mulberry enhanced transgenic plant resistance to the phytoplasma. Moreover, overexpression of Mu-GsSRK enhanced the expressions of pathogenesis-related protein 1, plant defensin, and cytochrome P450 protein CYP82C2 genes in transgenic plants inoculated with pathogens, which may contribute to the enhanced disease resistance against various pathogens. Finally, the DNA methylation dynamic patterns and functions of the differentially expressed and methylated genes were discussed. The results suggested that DNA methylation has important roles in mulberry responses to phytoplasma infection.

DNA Methylation Is Responsive to the Environment and Regulates the Expression of Biosynthetic Gene Clusters, Metabolite Production, and Virulence in Fusarium graminearum

Histone modifications play a significant role in the regulation of biosynthetic gene clusters (BGCs) in the phytopathogen Fusarium graminearum, by contrast, epigenetic regulation by DNA methyltransferases (DNMTs) is less documented. In this study, we characterized two DNMTs (FgDIM-2 and FgRID) in F. graminearum, with homologies to “Deficient in methylation” (DIM-2) and “Repeat-induced point (RIP) deficient” (RID) from Neurospora. The loss of DNMTs resulted in not only a decrease in average methylation density in the nutrient-poor, compared to nutrient-rich conditions, but also differences in the genes expressed between the WT and the DNMT mutant strains, implicating the external environment as an important trigger in altering DNA methylation patterns. Consequently, we observed significant changes in the regulation of multiple BGCs and alterations in the pathogenicity of the fungus.

The Competition between DNA Methylation and Demethylation is Associated with Transcription Regulation and Tumorigenesis

The mammalian DNA methylome is formed by two antagonizing processes, methylation by DNA methyltransferases (DNMT) and demethylation by ten-eleven translocation (TET) dioxygenases. Although the dynamics of either methylation or demethylation have been intensively studied in the past decade, their competition effect remains elusive. Here, we quantify the competition between DNA methylation and demethylation by the percentage of unmethylated CpGs within a partially methylated read from bisulfite sequencing. After verifying methylation competition by its strong association with the co-localization of DNMT and TET enzymes, we observe that methylation competition is strongly correlated with gene expression. In particular, during tumorigenesis, the elevation of methylation competition is associated with the repression of 40 ~ 60% of tumor suppressor genes, which cannot be explained by promoter hypermethylation alone. Furthermore, methylation competition can be used to stratify large undermethylated regions with negligible differences in average methylation into two subgroups with distinct chromatin accessibility and gene regulation patterns. Together, methylation competition represents a novel methylation metric important for transcription regulation and tumorigenesis and is largely distinct from conventional metrics, such as average methylation and methylation variation.

Tracing and tracking epiallele families in complex DNA populations

DNA methylation is a stable epigenetic modification, extremely polymorphic and driven by stochastic and deterministic events. Most of the current techniques used to analyse methylated sequences identify methylated cytosines (mCpGs) at a single-nucleotide level and compute the average methylation of CpGs in the population of molecules. Stable epialleles, i.e. CpG strings with the same DNA sequence containing a discrete linear succession of phased methylated/non-methylated CpGs in the same DNA molecule, cannot be identified due to the heterogeneity of the 5′–3′ ends of the molecules. Moreover, these are diluted by random unstable methylated CpGs and escape detection. We present here MethCoresProfiler, an R-based tool that provides a simple method to extract and identify combinations of methylated phased CpGs shared by all components of epiallele families in complex DNA populations. The methylated cores are stable over time, evolve by acquiring or losing new methyl sites and, ultimately, display high information content and low stochasticity. We have validated this method by identifying and tracing rare epialleles and their families in synthetic or in vivo complex cell populations derived from mouse brain areas and cells during postnatal differentiation. MethCoresProfiler is written in R language. The software is freely available at https://github.com/84AP/MethCoresProfiler/.

Processive and stochastic CHH methylation by plant DRM2 and CMT2 revealed by single-read methylome analysis

Cytosine methylome data is commonly generated through next-generation sequencing (NGS). Analyses of this data average methylation states of individual reads. We propose an alternate method of analysing single-read methylome data. Using this method, we identified patterns that relate to the mechanism of two plant non-CG methylating enzymes, DRM2 and CMT2: DRM2 has higher processivity than CMT2, and DRM2-methylated regions have higher variation among cells. Based on these patterns, we developed a classifier that predicts enzyme activity in different species and tissues. To facilitate further single-read analyses, we developed a genome browser optimised for visualising and analysing NGS data at single-read resolution.

DNA methylation of hypertension-related genes is influenced by the MTHFR 677TT genotype and riboflavin supplementation

Introduction:The C677T polymorphism in the folate metabolising enzyme methylenetetrahydrofolate reductase (MTHFR) is associated with hypertension. Riboflavin acts as a cofactor for MTHFR in one-carbon metabolism which generates methyl groups for utilisation in important biological reactions such as DNA methylation. Supplementation with riboflavin has previously been shown to lower blood pressure in individuals with the MTHFR 677TT genotype. The mechanism regulating this gene-nutrient interaction is currently unknown but may involve aberrant DNA methylation which has been implicated hypertension.Objectives:The aims of this study were to examine DNA methylation of hypertension-related genes in adults stratified by MTHFR C677T genotype and the effect of riboflavin supplementation on DNA methylation of these genes in individuals with the MTHFR 677TT genotype.Materials and Methods:We measured DNA methylation using pyrosequencing in a set of candidate genes associated with hypertension including angiotensin II receptor type 1 (AGTR1), G nucleotide binding protein subunit alpha 12 (GNA12), insulin-like growth factor 2 (IGF2) and nitric oxide synthase 3 (NOS3). Stored peripheral blood leukocyte samples from participants previously screened for the MTHFR C677T genotype who participated in targeted randomised controlled trials (1.6mg/d riboflavin or placebo for 16 weeks) at Ulster University were accessed for this analysis (n = 120).Results:There were significant differences in baseline average methylation between MTHFR CC and TT genotypes at NOS3 (p = 0.026) and AGTR1 (p = 0.045) loci. Riboflavin supplementation in the TT genotype group resulted in altered average methylation at IGF2 (p = 0.025) and CpG site-specific alterations at the AGTR1 and GNA12 loci.Conclusion:DNA methylation at genes related to hypertension were significantly different in individuals stratified by MTHFR genotype group. Furthermore, in MTHFR 677TT genotype individuals, there were concurrent alterations in DNA methylation at genes linked to hypertension in response to riboflavin supplementation. This is the largest study to date to demonstrate an interaction between DNA methylation of hypertension-related genes and riboflavin supplementation in adults with the MTHFR 677TT genotype. Further work using a genome-wide approach is required to better understand the role of riboflavin in altering DNA methylation in these genetically at-risk individuals.