Project description:human leukemia cells treated with vitamin C for 12 and 72hrs and mouse hematopoietic progenitor cells with knockdown and Tet2 restoration
Project description:T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive proliferation of T-lymphocytes usually associated with oncogenic activation of NOTCH1 signaling. Using a bone marrow transplantation approach, we have modeled murine CD4+ CD8+ T-ALL by overexpressing DNMT3A R882H in Tet2-/- multipotent progenitors. T-ALL derived from NOTCH1 L1601PdelP Tet2-/-, NOTCH1 L1601PdelP Tet2+/+ or TCL1A progenitors were used for comparison, as well as normal Tet2+/+ and Tet2-/- CD4+ CD8+ double positive (DP) thymocytes.
Project description:Ten-eleven translocation (Tet) enzymes (Tet1/2/3) mediate 5-methylcytosine (5mC) hydroxylation, which can facilitate DNA demethylation and thereby impact gene expression. Studied mostly for how mutant isoforms impact cancer, the normal roles for Tet enzymes during organogenesis are largely unknown. By analyzing compound mutant zebrafish, we discovered a requirement for Tet2/3 activity in embryonic heart for recruitment of epicardial progenitors, associated with defects in development of the atrial-ventricular canal (AVC). Through a combination of methylation, hydroxymethylation, and transcript profiling, the genes encoding the ActivinA subunit Inhbaa (in endocardium) and Sox9b (in myocardium) were implicated as demethylation targets of Tet2/3 and critical for organization of AVC-localized extracellular matrix (ECM), facilitating migration of epicardial progenitors onto the developing heart tube. This study elucidates essential DNA epigenetic modifications that govern gene expression changes during cardiac development with striking temporal and lineage specificities, highlighting complex interactions in multiple cell populations during development of the vertebrate heart.
Project description:The field of cancer genomics has been empowered by increasingly sophisticated inference tools to distinguish driver mutations from the vastly greater number of passenger mutations. Similarly, promoter DNA hypermethylation has been shown to drive cancer through inactivation of tumor suppressor genes (TSGs), but growing malignant populations also accrue pervasive stochastic epigenetic changes in DNA methylation (DNAme), which likely carry little functional impact. However, the development of DNAme inference methods has lagged behind, providing limited ability to robustly differentiate driver DNAme changes (epidrivers) from stochastic, passenger DNAme changes. To address this challenge, we developed MethSig, a statistical inference framework that accounts for the varying stochastic hypermethylation rates across the genome and between samples. MethSig estimates the background expected DNAme changes, thereby allowing the identification of epigenetically disrupted loci, where observed hypermethylation significantly exceeds expectation, potentially reflecting positive selection. We applied MethSig to reduced representation bisulfite sequencing (RRBS) data of 407 chronic lymphocytic leukemia (CLL) samples, including 304 CLLs collected in a prospective clinical trial. MethSig resulted in well-calibrated quantile-quantile (Q-Q) plots in contrast to ubiquitously used statistical methods, and reproducible inference of epidrivers across independent cohorts. MethSig provided robust inference in additional cancer types, including multiple myeloma (MM, n = 44) and ductal carcinoma in situ (DCIS, n = 24). To further validate MethSig’s inferences, selected CLL candidate epidrivers (DUSP22, RPRM, or SASH1) underwent CRISPR/Cas9 knockout in CLL cells, showing superior fitness in ibrutinib and fludarabine treatment compared with controls. Candidate epidrivers are enriched in known TSGs, and in genes hypermethylated or inactivated across cancer types. Notably, greater number of epidrivers was closely associated with adverse outcome in CLL in a multivariable model accounting for additional adverse prognostic marks. Application of MethSig to CLL relapsed after chemoimmunotherapy further identified relapse-specific epidrivers, enriched in TP53 targets as well as DNA damage pathway. Collectively, MethSig represents a novel framework for robust identification of epidrivers to chart the role of aberrant DNAme in cancer.
Project description:Reduced representation bisulfite sequencing (RRBS), which couples bisulfite conversion and next generation sequencing, is an innovative method that specifically enriches genomic regions with a high density of potential methylation sites and enables investigation of DNA methylation at single-nucleotide resolution. Recent advances in the Illumina DNA sample preparation protocol and sequencing technology have vastly improved sequencing throughput capacity. Although the new Illumina technology is now widely used, the unique challenges associated with multiplexed RRBS libraries on this platform have not been previously described. We have made modifications to the RRBS library preparation protocol to sequence multiplexed libraries on a single flow cell lane of the Illumina HiSeq 2000. Furthermore, our analysis incorporates a bioinformatics pipeline specifically designed to process bisulfite-converted sequencing reads and evaluate the output and quality of the sequencing data generated from the multiplexed libraries. We obtained an average of 42 million paired-end reads per sample for each flow-cell lane, with a high unique mapping efficiency to the reference human genome. Here we provide a roadmap of modifications, strategies, and trouble shooting approaches we implemented to optimize sequencing of multiplexed libraries on an a RRBS background.
Project description:We exploited the methylation genome-scale screening RRBS to correlate the RNA species physically associated with DNMT1 and proximal to the annotated genes to the methylation status of the corresponding loci. Out of 15275 non ambiguous gene loci identified by DNMT1 RIP-Seq, 9436 loci were covered by RRBS. These 9436 loci were clustered according to the fold of specific DNMT1 library peaks enrichment (defined as the ratio of the sum of the area under the curve of specific DNMT1 library peaks covering the gene loci). Genes were then stratified by the expression profile ultimately leading to the epitranscriptome map, a comprehensive map cross-referencing DNMT1-interacting transcripts to (i) DNA methylation and (ii) gene expression profile. Relationship between DNMT1-RNA interactions, DNA methylation and gene expression
Project description:Reduced representation bisulfite sequencing (RRBS) has been used to profile DNA methylation patterns in mammalian genomes such as human, mouse and rat. The methylome of the zebrafish, an important animal model, has not yet been characterized at base-pair resolution using RRBS. Therefore, we evaluated the technique of RRBS in this model organism by generating four single-nucleotide resolution DNA methylomes of adult zebrafish brain. We performed several simulations to show the distribution of fragments and enrichment of CpGs in different in silico reduced representation genomes of zebrafish. Four RRBS brain libraries generated 98 million sequenced reads and had higher frequencies of multiple mapping than equivalent human RRBS libraries. The zebrafish methylome indicates there is higher global DNA methylation in the zebrafish genome compared with its equivalent human methylome. This observation was confirmed by RRBS of zebrafish liver. High coverage CpG dinucleotides are enriched in CpG island shores more than in the CpG island core. We found that 45% of the mapped CpGs reside in gene bodies, and 7% in gene promoters. This analysis provides a roadmap for generating reproducible base-pair level methylomes for zebrafish using RRBS and our results provide the first evidence that RRBS is a suitable technique for global methylation analysis in zebrafish.
Project description:The aim of the project was to identify the tissue-specific DNA methylation patterns of selected horse tissues, derived from two germ layers, endodermal (liver and lung) and mesenchymal (cardiac striated muscle) origin. The comparative analysis of DNA methylation patterns of the genome fraction rich in CpG dinucleotides was investigated using Reduced Representation Bisulfite Sequencing (RRBS) technique.