Project description:Aberrant genetic and epigenetic variations drive malignant transformation and are hallmarks of cancer. Using PCR-free sample preparation we achieved the first in-depth whole genome (hydroxyl)-methylcytosine, single-base-resolution maps from a glioblastoma tumour/margin sample of a patient. Our data provide new insights into how genetic and epigenetic variations are interrelated. In the tumour, global hypermethylation with a depletion of 5-hydroxymethylcytosine was observed. The majority of single nucleotide variations were identified as cytosine-to-thymine deamination products within CpG context, where cytosine was preferentially methylated in the margin. Notably, we observe that cells neighbouring tumour cells display epigenetic alterations characteristic of the tumour itself although genetically they appear "normal". This shows the potential transfer of epigenetic information between cells that contributes to the intratumour heterogeneity of glioblastoma. Together, our reference (epi)-genome provides a human model system for future studies that aim to explore the link between genetic and epigenetic variations in cancer progression.
Project description:To be able to fully comprehend the contribution of the epigenome to embryonic development, it is important to understand how various components of the epigenome evolved. To date, a number of studies have thoroughly described various epigenetic mechanisms in both vertebrates and invertebrates, however there is currently a lack of high resolution epigenomic data corresponding to animals that form the invertebrate-vertebrate boundary. To that end, we have sequenced the genome of the European amphioxus (Branchiostoma lanceolatum) and explored various layers of its epigenome. Our whole genome bisulfite sequencing (MethylC-seq) approach revealed that amphioxus displays invertebrate-like, mosaic DNA methylation patterns. Nevertheless, we found significant DNA methylation remodeling events taking place during tissue differentiation, mostly consisting of developmental hypomethylation. This developmental loss of DNA methylation temporally coincides with the activation of the Tet protein orthologue in the amphioxus genome, suggestive of active demethylation. Furthermore, comparisons with chromatin accessibility data (ATAC-seq) demonstrate that this demethylation event affects cis regulatory elements, as previously described in vertebrates. Altogether, our study provides a rich developmental resource for studying epigenome evolution and demonstrates for the first time the existence of embryonic DNA methylation remodeling in an invertebrate chordate.
Project description:DNA methylation and hydroxymethylation are extensively reprogrammed in mammalian early embryogenesis. However, a comprehensive picture of DNA hydroxymethylation map across early embryo stages is lacking. Here, we develop “schmC-CATCH” (single-cell 5hmC chemical-assisted C-to-T conversion-enabled sequencing) to obtain quantitative, genome-wide landscape of the base-resolution DNA hydroxymethylome in mouse gametes and pre-implantation embryos from one-cell (PN1-PN5) to blastocyst stages. We revealed the dynamics of DNA hydroxymethylation and observed dramatically different 5hmC patterns on the paternal and maternal genomes. We found hotspots of DNA hydroxymethylation during mouse early embryo development, which are highly associated with young retroelements including LINE1. 5hmC is also associated with regulatory elements, indicating a potential epigenetic function during early embryogenesis. In addition, 5hmC is asymmetrically distributed at the chromosome level and can be used to track the cell and strand lineages during the first two embryo cleavages. Collectively, our work reveals the dynamics of active DNA demethylation during mouse pre-implantation development and provides an important resource for functional studies of epigenetic reprogramming in single cells.
Project description:Analysis of 5-hydroxymethylcytosine (5hmC) at single-base resolution has been largely limited to studies of stem cells or developmental stages. Given the potential importance of epigenetic events in hypertension, we have analyzed 5hmC and 5-methylcytosine (5mC) at single-base resolution in the renal outer medulla of the Dahl salt-sensitive rat and examined the effect of disease-relevant genetic or environmental alterations on 5hmC and 5mC patterns. Of CpG sites that fell within CpG islands, 11% and 1% contained significant 5mC and 5hmC, respectively. 5mC levels were substantially higher for genes with lower mRNA abundance and showed a prominent nadir around the transcription start site. In contrast, 5hmC levels were higher in genes with higher expression. Substitution of a 12.9-Mbp region of chromosome 13, which attenuates the hypertensive and renal injury phenotypes in salt-sensitive rats, or exposure to a high-salt diet, which accelerates the disease phenotypes, was associated with differential 5mC or 5hmC in several hundred CpG islands. Nearly 80% of the CpG islands that were differentially methylated in response to salt and associated with differential mRNA abundance were intragenic CpG islands. The substituted genomic segment had significant cis effects on mRNA abundance but not on DNA methylation. The study established base-resolution maps of 5mC and 5hmC in an in vivo model of disease and revealed several characteristics of 5mC and 5hmC important for understanding the role of epigenetic modifications in the regulation of organ systems function and complex diseases.
Project description:The effects of ethanol on developmental gene expression in sea urchins is compared to controls at three time points during gastrulation.
Project description:BackgroundThe transcription of developmental regulatory genes is often controlled by multiple cis-regulatory elements. The identification and functional characterization of distal regulatory elements remains challenging, even in tractable model organisms like sea urchins.ResultsWe evaluate the use of chromatin accessibility, transcription and RNA Polymerase II for their ability to predict enhancer activity of genomic regions in sea urchin embryos. ATAC-seq, PRO-seq, and Pol II ChIP-seq from early and late blastula embryos are manually contrasted with experimental cis-regulatory analyses available in sea urchin embryos, with particular attention to common developmental regulatory elements known to have enhancer and silencer functions differentially deployed among embryonic territories. Using the three functional genomic data types, machine learning models are trained and tested to classify and quantitatively predict the enhancer activity of several hundred genomic regions previously validated with reporter constructs in vivo.ConclusionsOverall, chromatin accessibility and transcription have substantial power for predicting enhancer activity. For promoter-overlapping cis-regulatory elements in particular, the distribution of Pol II is the best predictor of enhancer activity in blastula embryos. Furthermore, ATAC- and PRO-seq predictive value is stage dependent for the promoter-overlapping subset. This suggests that the sequence of regulatory mechanisms leading to transcriptional activation have distinct relevance at different levels of the developmental gene regulatory hierarchy deployed during embryogenesis.