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Epigenetic changes in Down syndrome leukemogenesis

ABSTRACT: Acute megakaryoblastic leukemia (AMKL) is more frequently seen in Down syndrome patients, where it is often preceded by a transient myeloproliferative disorder (DS-TMD). The development of DS-TMD and DS-AMKL require not only the presence of the trisomy 21 but also that of GATA1 mutations. However, despite extensive studies into the genetics of DS-AMKL, not much is known about the epigenetic deregulation associated with this disease. In order to understand how epigenetic changes at the DNA methylation level contribute to DS leukemogenesis we performed DNA methylation profiling at different stages of development of this disease and analyzed the dynamics of epigenetic reprogramming. Early genome-wide epigenetic changes can be detected in trisomy 21 fetal liver mononuclear cells, even prior to the development of hematological abnormalities. These early changes are characterized by marked loss of DNA methylation at genes associated with regulation of key developmental processes. This first wave of aberrant DNA hypomethylation is followed by a second wave of epigenetic reprogramming detected in blast cells from DS-TMD and DS-AMKL, characterized by gains of methylation. This second wave of hypermethylation targets a distinct set of genes, preferentially affecting genes involved in hematopoiesis and regulation of cell growth and proliferation.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE46167 | GEO | 2013/08/19

SECONDARY ACCESSION(S): PRJNA197487

REPOSITORIES: GEO

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Project description:Background: Trisomy 21 causes Down syndrome (DS), but the mechanisms by which the extra chromosome leads to deficient intellectual and immune function are not well understood. Results: Here, we profile CpG methylation in DS and control cerebral and cerebellar cortex of adults and cerebrum of fetuses. We purify neuronal and non-neuronal nuclei and T-lymphocytes and find biologically relevant genes with DS-specific methylation (DS-DM) in brain cells. Some genes show brain-specific DS-DM, while others show stronger DS-DM in T cells. Both 5-methyl-cytosine and 5-hydroxy-methyl-cytosine contribute to the DS-DM. Thirty percent of genes with DS-DM in adult brain cells also show DS-DM in fetal brains, indicating early onset of these epigenetic changes, and we find early maturation of methylation patterns in DS brain and lymphocytes. Some, but not all, of the DS-DM genes show differential expression. DS-DM preferentially affected CpGs in or near specific transcription factor binding sites, implicating a mechanism involving altered transcription factor binding. Methyl-seq of brain DNA from mouse models with sub-chromosomal duplications mimicking DS reveals partial but significant overlaps with human DS-DM and shows that multiple chromosome 21 genes contribute to the downstream epigenetic effects. Conclusions: These data point to novel biological mechanisms in DS and have general implications for trans effects of chromosomal duplications and aneuploidies on epigenetic patterning. Bisulfite converted DNA from 119 samples from Down syndrome patients and controls were hybridised to the Illumina Infinium 450k Human Methylation Beadchip. In addition, we re-analyzed 6 Down syndrome and 6 control cerebellum DNA samples on the 450K BeadChips using an adaptation of the Illumina probe preparation protocol (TrueMethyl kit; Cambridge Epigenetics, CEGX), in which parallel analyses of bisulfite and oxidative bisulfite DNA for each sample allows assessment of the relative contributions of 5mC and 5hmC to net methylation.

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Epigenetic changes in Down syndrome leukemogenesis

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