Using the Illumina 450K array and a stringent statistical analysis with age and gender correction, we report genome-wide differences in DNA methylation between pathology-free regions derived from ...human multiple sclerosis-affected and control brains. Differences were subtle, but widespread and reproducible in an independent validation cohort. The transcriptional consequences of differential DNA methylation were further defined by genome-wide RNA-sequencing analysis and validated in two independent cohorts. Genes regulating oligodendrocyte survival, such as BCL2L2 and NDRG1, were hypermethylated and expressed at lower levels in multiple sclerosis-affected brains than in controls, while genes related to proteolytic processing (for example, LGMN, CTSZ) were hypomethylated and expressed at higher levels. These results were not due to differences in cellular composition between multiple sclerosis and controls. Thus, epigenomic changes in genes affecting oligodendrocyte susceptibility to damage are detected in pathology-free areas of multiple sclerosis-affected brains.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Despite representing an important source of genetic variation, tandem repeats (TRs) remain poorly studied due to technical difficulties. We hypothesized that TRs can operate as expression (eQTLs) and ...methylation (mQTLs) quantitative trait loci. To test this we analyzed the effect of variation at 4849 promoter-associated TRs, genotyped in 120 individuals, on neighboring gene expression and DNA methylation. Polymorphic promoter TRs were associated with increased variance in local gene expression and DNA methylation, suggesting functional consequences related to TR variation. We identified >100 TRs associated with expression/methylation levels of adjacent genes. These potential eQTL/mQTL TRs were enriched for overlaps with transcription factor binding and DNaseI hypersensitivity sites, providing a rationale for their effects. Moreover, we showed that most TR variants are poorly tagged by nearby single nucleotide polymorphisms (SNPs) markers, indicating that many functional TR variants are not effectively assayed by SNP-based approaches. Our study assigns biological significance to TR variations in the human genome, and suggests that a significant fraction of TR variations exert functional effects via alterations of local gene expression or epigenetics. We conclude that targeted studies that focus on genotyping TR variants are required to fully ascertain functional variation in the genome.
While population studies have resulted in detailed maps of genetic variation in humans, to date there are few robust maps of epigenetic variation. We identified sites containing clusters of CpGs with ...high inter-individual epigenetic variation, termed Variably Methylated Regions (VMRs) in five purified cell types. We observed that VMRs occur preferentially at enhancers and 3' UTRs. While the majority of VMRs have high heritability, a subset of VMRs within the genome show highly correlated variation in trans, forming co-regulated networks that have low heritability, differ between cell types and are enriched for specific transcription factor binding sites and biological pathways of functional relevance to each tissue. For example, in T cells we defined a network of 95 co-regulated VMRs enriched for genes with roles in T-cell activation; in fibroblasts a network of 34 co-regulated VMRs comprising all four HOX gene clusters enriched for control of tissue growth; and in neurons a network of 18 VMRs enriched for roles in synaptic signaling. By culturing genetically-identical fibroblasts under varying environmental conditions, we experimentally demonstrated that some VMR networks are responsive to the environment, with methylation levels at these loci changing in a coordinated fashion in trans dependent on cellular growth. Intriguingly these environmentally-responsive VMRs showed a strong enrichment for imprinted loci (p<10-80), suggesting that these are particularly sensitive to environmental conditions. Our study provides a detailed map of common epigenetic variation in the human genome, showing that both genetic and environmental causes underlie this variation.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
There is growing recognition that epivariations, most often recognized as promoter hypermethylation events that lead to gene silencing, are associated with a number of human diseases. However, little ...information exists on the prevalence and distribution of rare epigenetic variation in the human population. In order to address this, we performed a survey of methylation profiles from 23,116 individuals using the Illumina 450k array. Using a robust outlier approach, we identified 4,452 unique autosomal epivariations, including potentially inactivating promoter methylation events at 384 genes linked to human disease. For example, we observed promoter hypermethylation of BRCA1 and LDLR at population frequencies of ∼1 in 3,000 and ∼1 in 6,000, respectively, suggesting that epivariations may underlie a fraction of human disease which would be missed by purely sequence-based approaches. Using expression data, we confirmed that many epivariations are associated with outlier gene expression. Analysis of variation data and monozygous twin pairs suggests that approximately two-thirds of epivariations segregate in the population secondary to underlying sequence mutations, while one-third are likely sporadic events that occur post-zygotically. We identified 25 loci where rare hypermethylation coincided with the presence of an unstable CGG tandem repeat, validated the presence of CGG expansions at several loci, and identified the putative molecular defect underlying most of the known folate-sensitive fragile sites in the genome. Our study provides a catalog of rare epigenetic changes in the human genome, gives insight into the underlying origins and consequences of epivariations, and identifies many hypermethylated CGG repeat expansions.
Abstract Background Early childhood malnutrition affects 113 million children worldwide, impacting health and increasing vulnerability for cognitive and behavioral disorders later in life. Molecular ...signatures after childhood malnutrition, including the potential for intergenerational transmission, remain unexplored. Methods We surveyed blood DNA methylomes (~483,000 individual CpG sites) in 168 subjects across two generations (G1,G2), including 50 G1 individuals hospitalized during the first year of life for moderate to severe protein energy malnutrition, then followed up to 48 years in the Barbados Nutrition Study. Attention deficits and cognitive performance were evaluated with Connors Adult Attention Rating Scale (CAARS) and Wechsler Abbreviated Scale of Intelligence (WASI). Expression of nutrition-sensitive genes was explored by qRT-PCR in rat prefrontal cortex. Results We identified altogether 134 nutrition-sensitive differentially methylated genomic regions (DMR), with the overwhelming majority (87%) specific for G1. Multiple neuropsychiatric risk genes, including COMT, IFNG, MIR200B, SYNGAP1 and VIP2R showed associations of specific methyl-CpGs with attention and IQ. Interferon Gamma ( IFNG ) expression was decreased in prefrontal cortex of rats showing attention deficits after developmental malnutrition. Conclusions Early childhood malnutrition entails long lasting epigenetic signatures associated with liability for attention and cognition, and limited potential for intergenerational transmission.
Certain human traits such as neurodevelopmental disorders (NDs) and congenital anomalies (CAs) are believed to be primarily genetic in origin. However, even after whole-genome sequencing (WGS), a ...substantial fraction of such disorders remain unexplained. We hypothesize that some cases of ND-CA are caused by aberrant DNA methylation leading to dysregulated genome function. Comparing DNA methylation profiles from 489 individuals with ND-CAs against 1534 controls, we identify epivariations as a frequent occurrence in the human genome. De novo epivariations are significantly enriched in cases, while RNAseq analysis shows that epivariations often have an impact on gene expression comparable to loss-of-function mutations. Additionally, we detect and replicate an enrichment of rare sequence mutations overlapping CTCF binding sites close to epivariations, providing a rationale for interpreting non-coding variation. We propose that epivariations contribute to the pathogenesis of some patients with unexplained ND-CAs, and as such likely have diagnostic relevance.
DNA methylation is an epigenetic modification involved in regulatory processes such as cell differentiation during development, X-chromosome inactivation, genomic imprinting and susceptibility to ...complex disease. However, the dynamics of DNA methylation changes between humans and their closest relatives are still poorly understood. We performed a comparative analysis of CpG methylation patterns between 9 humans and 23 primate samples including all species of great apes (chimpanzee, bonobo, gorilla and orangutan) using Illumina Methylation450 bead arrays. Our analysis identified ∼800 genes with significantly altered methylation patterns among the great apes, including ∼170 genes with a methylation pattern unique to human. Some of these are known to be involved in developmental and neurological features, suggesting that epigenetic changes have been frequent during recent human and primate evolution. We identified a significant positive relationship between the rate of coding variation and alterations of methylation at the promoter level, indicative of co-occurrence between evolution of protein sequence and gene regulation. In contrast, and supporting the idea that many phenotypic differences between humans and great apes are not due to amino acid differences, our analysis also identified 184 genes that are perfectly conserved at protein level between human and chimpanzee, yet show significant epigenetic differences between these two species. We conclude that epigenetic alterations are an important force during primate evolution and have been under-explored in evolutionary comparative genomics.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The present study aimed to establish a better marker for the assessment of coronary artery disease (CAD).
One hundred patients of CAD (aged 20–60 years) of both sex and patients of hypertension with ...symptoms of CAD were selected for the study.50 age and sex matched healthy controls were chosen for the present study. Serum total cholesterol, triglycerides and HDL-C were estimated in Simens Dimensions RxL. LDL-C, VLDL-C were calculated by Friedwald Formula while non-HDL-C was calculated by subtracting HDL-C level from total cholesterol level. The comparison of non-HDL-C and friedwald calculated LDL-C was made in terms of independent‘t’ test, serum TG levels (TG ≤ 200 mg/dl and TG > 200 mg/dl) and area under receiver operating characteristic (AUROC) curve.
The non-HDL-C levels (mean ± S.D) were higher in both test and control groups to that of the levels of friedwald calculated LDL-C. The area under receiver operating characteristic (AUROC) curve was significantly higher for non-HDL-C than for friedwald calculated LDL-C. The predictive value of non-HDL-C and friedwald calculated LDL-C were also compared in group A (serum TG ≤ 200 mg/dl) and group B (serum TG > 200 mg/dl). Non-HDL-C levels showed a significant difference in both the groups while the results were non-significant to that of friedwald calculated LDL. Thus, non-HDL-C is much specific and sensitive parameter for assessment of CAD risk. Moreover, non-HDL-C levels can also be done in non-fasting state with accuracy, thereby, it is patient friendly parameter. Therefore, the authors strongly suggest the incorporation of non-HDL-C in routine lipid profile panel.
Although DNA methylation is the best characterized epigenetic mark, the mechanism by which it is targeted to specific regions in the genome remains unclear. Recent studies have revealed that local ...DNA methylation profiles might be dictated by cis-regulatory DNA sequences that mainly operate via DNA-binding factors. Consistent with this finding, we have recently shown that disruption of CTCF-binding sites by rare single nucleotide variants (SNVs) can underlie cis-linked DNA methylation changes in patients with congenital anomalies. These data raise the hypothesis that rare genetic variation at transcription factor binding sites (TFBSs) might contribute to local DNA methylation patterning. In this work, by combining blood genome-wide DNA methylation profiles, whole genome sequencing-derived SNVs from 247 unrelated individuals along with 133 predicted TFBS motifs derived from ENCODE ChIP-Seq data, we observed an association between the disruption of binding sites for multiple TFs by rare SNVs and extreme DNA methylation values at both local and, to a lesser extent, distant CpGs. While the majority of these changes affected only single CpGs, 24% were associated with multiple outlier CpGs within ±1kb of the disrupted TFBS. Interestingly, disruption of functionally constrained sites within TF motifs lead to larger DNA methylation changes at nearby CpG sites. Altogether, these findings suggest that rare SNVs at TFBS negatively influence TF-DNA binding, which can lead to an altered local DNA methylation profile. Furthermore, subsequent integration of DNA methylation and RNA-Seq profiles from cardiac tissues enabled us to observe an association between rare SNV-directed DNA methylation and outlier expression of nearby genes. In conclusion, our findings not only provide insights into the effect of rare genetic variation at TFBS on shaping local DNA methylation and its consequences on genome regulation, but also provide a rationale to incorporate DNA methylation data to interpret the functional role of rare variants.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
X chromosome inactivation (XCI) is an epigenetic mechanism that silences the majority of genes on one X chromosome in females. Previous studies have suggested that the spread of XCI might be ...facilitated in part by common repeats such as long interspersed nuclear elements (LINEs). However, owing to the unusual sequence content of the X and the nonrandom distribution of genes that escape XCI, it has been unclear whether the correlation between repeat elements and XCI is a functional one. To test the hypothesis that the spread of XCI shows sequence specificity, we have analyzed the pattern of XCI in autosomal chromatin by performing DNA methylation profiling in six unbalanced X;autosome translocations. Using promoter hypermethylation as an epigenetic signature of XCI, we have determined the inactivation status of 1050 autosomal genes after translocation onto an inactive derivative X. By performing a comparative sequence analysis of autosomal genes that are either subject to or escape the X inactivation signal, we identified a number of common repetitive elements, including L1 and L2 LINEs, and DNA motifs that are significantly enriched around inactive autosomal genes. We show that these same motifs predominantly map to L1P repeat elements, are significantly enriched on the X chromosome versus the autosomes and also occur at higher densities around X-linked genes that are subject to X inactivation compared with those that escape X inactivation. These results are consistent with a potential causal relationship between DNA sequence features such as L1s and the spread of XCI, lending strong support to Mary Lyon's 'repeat hypothesis'.
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