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Comprehensive array CGH of normal karyotype Myelodysplastic syndrome reveals hidden recurrent and individual genomic copy number aberrations with prognostic relevance

ABSTRACT: About 40% of patients with myelodysplastic syndromes (MDS) present with a normal karyotype and they are facing different courses of disease. To advance the biological understanding and find molecular prognostic markers we performed a high resolution oligonucleotide array study of 107 MDS patients (FAB) with a normal karyotype. Recurrent hidden deletions overlapping with known cytogenetic aberrations or sites of known tumor associated genes were identified in 4q24 (TET2, 2x), 5q31.2 (2x), 7q22.1 (3x) and 21q22.12 (RUNX1, 2x). One patient with a 7q22.1 had an additional 5q31.2 deletion of the AML/MDS region; the smallest deletion identified so far and includes the putative tumor suppressor (ts) genes EGR1 and CTNNA1. One TET2 deletion was homozygous and one heterozygous, with a missense mutation in the remaining allele, further supporting its role as ts gene. Besides these recurrent alterations, additional individual imbalances were found in 34 cases; in total 42/107 (39%) cases had genomic imbalances, deletions were more frequent than gains. These patients had an inferior survival as compared with the rest of the patients (P=0.002). This study emphasizes the heterogeneity of MDS but points to interesting genes which may have diagnostic and prognostic impact.

ORGANISM(S): Homo sapiens

PROVIDER: GSE24602 | GEO | 2011/01/30

SECONDARY ACCESSION(S): PRJNA132395

REPOSITORIES: GEO

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Project description:TET2 is a close relative of TET1, an enzyme that converts 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. The gene encoding TET2 resides at chromosome 4q24, in a region showing recurrent microdeletions and copy-neutral loss of heterozygosity (CN-LOH) in patients with diverse myeloid malignancies. Somatic TET2 mutations are frequently observed in myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), MDS/MPN overlap syndromes including chronic myelomonocytic leukaemia (CMML), acute myeloid leukaemias (AML) and secondary AML (sAML). We show here that TET2 mutations associated with myeloid malignancies compromise catalytic activity. Bone marrow samples from patients with TET2 mutations displayed uniformly low levels of 5hmC in genomic DNA compared to bone marrow samples from healthy controls. Moreover, small hairpin RNA (shRNA)-mediated depletion of Tet2 in mouse haematopoietic precursors skewed their differentiation towards monocyte/macrophage lineages in culture. There was no significant difference in DNA methylation between bone marrow samples from patients with high 5hmC versus healthy controls, but samples from patients with low 5hmC showed hypomethylation relative to controls at the majority of differentially methylated CpG sites. Our results demonstrate that Tet2 is important for normal myelopoiesis, and suggest that disruption of TET2 enzymatic activity favours myeloid tumorigenesis. Measurement of 5hmC levels in myeloid malignancies may prove valuable as a diagnostic and prognostic tool, to tailor therapies and assess responses to anticancer drugs. Genome wide DNA methylation profiling of patients samples with various myeloid malignancies and diffrential levels of 5hmC.The Illumina Infinium 27k Human DNA methylation Beadchip v1.2 was used to obtain DNA methylation profiles across approximately 27,000 CpGs in bone marrow samples and occasionally peripheral blood samples. Samples included 28 control healthy bone marrows, 29 patients samples with low 5hmC levels (7 patients with wild-type TET2 and 22 mutant TET2) and 24 with high levels of 5hmC (22 with wild-type TET2 and 2 mutant TET2). Bisulphite converted DNA from 81 samples was hybridised to the Illumina Infinium 27k Human Methylation Beadchip v1.2

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Comprehensive array CGH of normal karyotype Myelodysplastic syndrome reveals hidden recurrent and individual genomic copy number aberrations with prognostic relevance

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