Project description:The intent of the experiment was to construct molecular SNP-binning markers of a Col-0 x Pat RIL population, for sensitive QTL mapping. We performed Illumina low-coverage DNA sequencing of plant tissues.
Project description:We mapped DNA methylation in 580 animal species (535 vertebrates, 45 invertebrates), resulting in 2443 genome-scale, base-resolution DNA methylation profiles of primary tissue samples from various organs. Reference-genome independent analysis of this comprehensive dataset defined a “genomic code” of DNA methylation, which allowed us to predict global and locus-specific DNA methylation from the DNA sequence within and across species. This code appears broadly conserved throughout vertebrate evolution, with two major transitions – once in the first vertebrates and again with the emergence of reptiles. Beyond the central role of species-specific DNA sequence composition, our dataset identified the tissue type and the individual as two main sources of DNA methylation variability within species. Tissue type was the dominant factor in fish, birds, and mammals, while in invertebrates, reptiles, and amphibians both factors were similarly strong. Cross-species comparisons focusing on heart and liver tissues supported a highly conserved role of DNA methylation for tissue type and identity and cross-mapping based promoter methylation analysis revealed divergence at specific genes. In summary, this study establishes a large resource of vertebrate and invertebrate DNA methylomes, it showcases the power of reference-free epigenome analysis in species for which no reference genomes are available, and it contributes an epigenetic perspective to the study of vertebrate evolution.
Project description:Sequencing based approaches have led to new insights about DNA methylation. While many different techniques for genome-scale mapping of DNA methylation have been employed, throughput has been a key limitation for most. To further facilitate the mapping of DNA methylation, we describe a protocol for gel-free multiplexed reduced representation bisulfite sequencing (mRRBS) that reduces the workload dramatically and enables processing of 96 or more samples per week. mRRBS achieves similar CpG coverage as the original RRBS protocol, while the higher throughput and lower cost make it better suited for large-scale DNA methylation mapping studies including cohorts of cancer samples.
Project description:Genome-wide DNA methylation mapping uncovers epigenetic changes associated with animal development, environmental adaptation, and species evolution. To address the lack of high-throughput methods for studying DNA methylation in non-model organisms, we developed an integrated approach for studying DNA methylation differences without a reference genome. Experimentally, our method relies on an optimized 96-well protocol for reduced representation bisulfite sequencing (RRBS), which we have validated in nine species (human, mouse, rat, cow, dog, chicken, zebrafish, carp, and sea bass). Bioinformatically, we developed the RefFreeDMA software (http://RefFreeDMA.computational-epigenetics.org) to deduce ad hoc genomes directly from RRBS reads and to pinpoint differentially methylated regions. These regions are interpreted using motif enrichment analysis and/or cross-mapping to annotated genomes. We validated our method by reference-free analysis of cell type-specific DNA methylation in the blood of human, cow, and carp. In summary, we present a cost-effective method for epigenome analysis in ecology and evolution, which enables epigenome-wide association studies in natural populations and species without a reference genome.
Project description:Sequencing based approaches have led to new insights about DNA methylation. While many different techniques for genome-scale mapping of DNA methylation have been employed, throughput has been a key limitation for most. To further facilitate the mapping of DNA methylation, we describe a protocol for gel-free multiplexed reduced representation bisulfite sequencing (mRRBS) that reduces the workload dramatically and enables processing of 96 or more samples per week. mRRBS achieves similar CpG coverage as the original RRBS protocol, while the higher throughput and lower cost make it better suited for large-scale DNA methylation mapping studies including cohorts of cancer samples. Libraries of 96 human samples
Project description:Ethnic differences in human DNA methylation have been shown for a number of CpG sites, but the genome-wide patterns and extent of these differences are unknown. In addition, whether the genetic control of polymorphic DNA methylation is population-specific has not been investigated. Here we measure DNA methylation near the transcription start sites of over 14,000 genes in 180 cell lines derived from one African and one European population. We find population-specific patterns of DNA methylation at over a third of all genes. Furthermore, although the methylation at over a thousand CpG sites is heritable, these heritabilities are also distinctly different between populations, suggesting extensive divergence in the genetic control of DNA methylation. In support of this, genetic mapping of DNA methylation reveals that there is also little overlap in genetic associations between populations. This population-specificity is supported by the patterns of DNA methylation in several hundred brain samples, suggesting it holds in vivo and across tissues. These results suggest that DNA methylation is highly divergent between populations, and that this divergence may be due in large part to complex epistasis or gene x environment interactions.
Project description:Methylation of cytosines (5meC) is a widespread heritable DNA modification. During mammalian development, two global demethylation events are followed by waves of de novo DNA methylation. In vivo mechanisms of DNA methylation establishment are largely uncharacterized. Here we use Saccharomyces cerevisiae as a system lacking DNA methylation to define the chromatin features influencing the activity of the murine DNMT3B. Our data demonstrate that DNMT3B and H3K4 methylation are mutually exclusive and that DNMT3B is co-localized with H3K36 methylated regions. In support of this observation, DNA methylation analysis in yeast strains without Set1 and Set2 show an increase of relative 5meC levels at the TSS and a decrease in the gene-body, respectively. We extend our observation to the murine male germline, where H3K4me3 is strongly anti-correlated while H3K36me3 correlates with accelerated DNA methylation. These results show the importance of H3K36 methylation for gene-body DNA methylation in vivo. Nucleosome mapping in yeast
Project description:An Infinium microarray platform (GPL28271, HorvathMammalMethylChip40) was used to generate DNA methylation data from synthetic DNA from 3 species. The DNA samples from each species were enzymatically manipulated so that they would exhibit 0%, 25%, 50%, 75% and 100% percent methylation at each CpG location, respectively. The variable “ProportionMethylated” (with ordinal values 0, 0.25, 0.5, 0.75, 1) can be interpreted as a benchmark for each CpG that maps to the respective genome. Thus, the DNA methylation levels of each CpG are expected to have a high positive correlation with ProportionMethylated across the arrays measurement from a given species. The mammalian array was applied to synthetic DNA data from 3 species: human (n=10 mammalian arrays, 2 per methylation level), mouse (n=20, 4 per methylation level), and rat (n=15, 3 per methylation level).