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TET2 deficiency promotes MDS-associated leukemogenesis

ABSTRACT: Loss of function TET2 mutations are frequently seen in myelodysplastic syndrome (MDS) patients. Previous studies have demonstrated that TET2 deficiency enhances maintenance of MDS hematopoietic stem and progenitor cells (HSPCs). Nonetheless, the pathogenic role of TET2 in MDS progression remains elusive. Here, we demonstrate Tet2 knockout (KO) markedly accelerated malignant transformation in Nup98-HoxD13 (NHD13) transgenic mice and promotes leukemogenesis of HoxA9 transduction/transplant mice. Consistently, low TET2 level cooperating with high HOXA9 level predicts poor outcome of MDS patients. Notably, Tet2 KO conferred a clonal advantage to the HSPCs of NHD13 mice. Whole-exome sequencing revealed that Tet2 KO facilitates accumulation of mutations at genes associated with leukemogenesis, including Arih2, whose loss of function promotes MDS cells proliferation. Using 5-hydroxymethylcytosine immunoprecipitation coupled with high-throughput sequencing analysis, we found while Tet2 deletion decreased overall 5hmC levels, it also increased 5hmC distribution at certain mutation loci such as Arih2. Vitamin C treatment, which mimics Tet2/Tet3 restoration, blocked disease progression in Tet2-deficient NHD13 mice. Collectively, our findings demonstrate that TET2 activity governs occurrence of secondary mutations in MDS HSPCs, providing a rationale for enhancing TETs function to block MDS-malignant transformation.

ORGANISM(S): Mus musculus

PROVIDER: GSE213591 | GEO | 2022/10/12

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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TET2 deficiency promotes MDS-associated leukemogenesis

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