We conducted a genome-wide DNA methylation analysis in CD19 (+) B-cells from chronic lymphocytic leukemia (CLL) patients and normal control samples using reduced representation bisulfite sequencing (RRBS). The methylation status of 1.8-2.3 million CpGs in the CLL genome was determined; about 45% of these CpGs were located in more than 23,000 CpG islands (CGIs). While global CpG methylation was similar between CLL and normal B-cells, 1764 gene promoters were identified as being differentially methylated in at least one CLL sample when compared with normal B-cell samples. Nineteen percent of the differentially methylated genes were involved in transcriptional regulation. Aberrant hypermethylation was found in all HOX gene clusters and a significant number of WNT signaling pathway genes. Hypomethylation occurred more frequently in the gene body including introns, exons, and 3'-UTRs in CLL. The NFATc1 P2 promoter and first intron was found to be hypomethylated and correlated with upregulation of both NFATc1 RNA and protein expression levels in CLL suggesting that an epigenetic mechanism is involved in the constitutive activation of NFAT activity in CLL cells. This comprehensive DNA methylation analysis will further our understanding of the epigenetic contribution to cellular dysfunction in CLL.
High-throughput microarray technologies were used to study DNA methylation accompanied by transcriptional changes in follicular lymphoma (FL). Using Methylated CpG Island Amplification with Microarrays (MCAM) to study CpG Island (CGI) DNA methylation in follicular lymphoma (FL) we discovered widespread hypermethylation of homeobox genes and previously identified targets of polycomb repressive complex 2 (PRC2) in cell lines and primary tumors, but not in benign follicular hyperplasia (BFH). DNA methylation for HOXA11, HOXD10, HOXB7, HOXC12, PAX6, LHX9, SFMBT2, EN2 and PAX7 was independently validated in the RL cell line and HOXA11, HOXD10, PAX6 and EN2 in primary tumors. Combined Bisulfite Restriction Analysis (COBRA) also established DNA methylation for the previously identified PRC2 targets DCC, DES, GAD2, AQP5, GPR61, GRIA4, GJD2 and AMPH in FL but not in BFH. Gene expression analyses revealed 411 genes that were hypermethylated and transcriptionally repressed in RL, 74% of which were re-activated by the demethylating agent 5-aza-2′-deoxycytidine (5-azaD) plus or minus the histone deacetylase inhibitor trichostatin A (TSA). Forty genes were also down-regulated in primary FL. Our results suggest that extensive hypermethylation in promoters of polycomb target genes is a characteristic of FL and that loss of expression of certain SUZ12 target genes could be functionally relevant for lymphomagenesis.
BackgroundFollicular lymphoma (FL) is a form of non-Hodgkin's lymphoma (NHL) that arises from germinal center (GC) B-cells. Despite the significant advances in immunotherapy, FL is still not curable. Beyond transcriptional profiling and genomics datasets, there currently is no epigenome-scale dataset or integrative biology approach that can adequately model this disease and therefore identify novel mechanisms and targets for successful prevention and treatment of FL.Methodology/Principal FindingsWe performed methylation-enriched genome-wide bisulfite sequencing of FL cells and normal CD19+ B-cells using 454 sequencing technology. The methylated DNA fragments were enriched with methyl-binding proteins, treated with bisulfite, and sequenced using the Roche-454 GS FLX sequencer. The total number of bases covered in the human genome was 18.2 and 49.3 million including 726,003 and 1.3 million CpGs in FL and CD19+ B-cells, respectively. 11,971 and 7,882 methylated regions of interest (MRIs) were identified respectively. The genome-wide distribution of these MRIs displayed significant differences between FL and normal B-cells. A reverse trend in the distribution of MRIs between the promoter and the gene body was observed in FL and CD19+ B-cells. The MRIs identified in FL cells also correlated well with transcriptomic data and ChIP-on-Chip analyses of genome-wide histone modifications such as tri-methyl-H3K27, and tri-methyl-H3K4, indicating a concerted epigenetic alteration in FL cells.Conclusions/SignificanceThis study is the first to provide a large scale and comprehensive analysis of the DNA methylation sequence composition and distribution in the FL epigenome. These integrated approaches have led to the discovery of novel and frequent targets of aberrant epigenetic alterations. The genome-wide bisulfite sequencing approach developed here can be a useful tool for profiling DNA methylation in clinical samples.
To better engage our graduate students, we asked them to describe their research strategy and challenges, helpful research support services, and their preferred venue for learning research skills. We conducted a thematic analysis and found that participants' top reported research strategies included "Research Topic Development" and "Literature Review," while their challenges cited "Finding and Evaluating Information" and "Access Issues." The students mentioned "Library Databases" most frequently as helpful and websites were their most preferred learning venue. We found evidence that discipline-specific library instruction may be more relevant than large, in-person orientations and discovered a concerning trend of situational challenges.
Umbilical cord blood is highly enriched for hematopoietic progenitor cells at different lineage commitment stages. We have developed a protocol for isolating precursor B-cells at four different stages of differentiation. Because genes are expressed and epigenetic modifications occur in a tissue specific manner, it is vital to discriminate between tissues and cell types in order to be able to identify alterations in the genome and the epigenome that may lead to the development of disease. This method can be adapted to any type of cell present in umbilical cord blood at any stage of differentiation.
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