Differential methylation in CN-AML preferentially targets non-CGI regions and is dictated by DNMT3A mutational status and associated with predominant hypomethylation of HOX genes
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ABSTRACT: The study investigated the abberrent DNA methylation in correlation with gene expression in cytogenetic normal acute myeloid leukemia. CN-AML blasts isolated from patient bone marrow aspriation were compared to CD34+ cell population from healthy donors by DNA methylation array and affymetrix gene expression microarray.
Project description:The study investigated the abberrent DNA methylation in correlation with gene expression in cytogenetic normal acute myeloid leukemia. CN-AML blasts isolated from patient bone marrow aspriation were compared to CD34+ cell population from healthy donors by DNA methylation array and affymetrix gene expression microarray. Bisulfited genomic DNA from patients and normal materials were hybirdized to Illumia Infinium Human Methylation 450K Beadchip. Gene expression profiling on selected patient cohort are publish aviable.
Project description:The extent and role of aberrant DNA methylation in promoter CpG islands (CGIs) have been extensively studied in leukemia and other malignancies. Still, CGIs represent only a small fraction of the methylome. We aimed to characterize genome-wide differential methylation of cytogenetically normal AML (CN-AML) cells compared with normal CD34(+) bone marrow cells using the Illumina 450K methylation array. Differential methylation in CN-AML was most prominent in genomic areas far from CGIs, in so called open sea regions. Furthermore, differential methylation was specifically found in genes encoding transcription factors (TFs), with WT1 being the most differentially methylated TF. Among genetic mutations in AML, DNMT3A mutations showed the most prominent association with the DNA methylation pattern, characterized by hypomethylation of CGIs (as compared with DNMT3A wild type cases). The differential methylation in DNMT3A mutant cells vs. wild type cells was predominantly found in HOX genes, which were hypomethylated. These results were confirmed and validated in an independent CN-AML cohort. In conclusion, we show that, in CN-AML, the most pronounced changes in DNA methylation occur in non-CGI regions and that DNMT3A mutations confer a pattern of global hypomethylation that specifically targets HOX genes.
Project description:Severe congenital neutropenia (CN) is a pre-leukemia syndrome that, in the majority of patients, is caused by heterogeneous ELANE mutations encoding neutrophil elastase (NE). To study leukemogenesis associated with CN we generated CN and CN/AML patient-specific induced pluripotent stem cells (iPSCs). Additional mutations in leukemia-relevant genes, CSF3R and RUNX1, were introduced using CRISPR/Cas9 gene-editing. Consequently, we performed in vitro embryoid body (EB)-based hematopoietic and myeloid differentiation of generated iPSC lines. On day 14-17 of EB-based differentiation, iPSC-derived CD45+CD34+ cells were harvested and mRNA was isolated using RNeasy Mini- or Micro Kit (Qiagen). Sequencing libraries were prepared using the TruSeq RNA Sample Prep Kit (Illumina). Poly (A) selected single-read and pair-read sequencing libraries were sequenced on the Illumina platform in order to compare the transcriptomes of CN and CN/AML iPSCs-derived HSPCs from 2 CN/AML patients. Next, we identified that BAALC knockout resulted in a dramatic induction of granulocytic differentiation and a significant reduction in proliferation of CN/AML iPSC-derived HSPCs. To identify BAALC-dependent leukemia-associated gene expression, we compared the transcriptomes of CN/AML iPSCs before and after BAALC KO using a similar approach described above for CN and CN/AML iPSCs-derived HSPCs.