Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

TET2 is mutated/deleted with high frequencies in multiple forms of myeloid malignancies including MDS, CMML, MPN, and AML. However, little is known regarding the biological function of TET2 and its role in the pathogenesis of myeloid malignancies. To study the function of TET2 in vivo, we generated a Tet2 knock out mouse model. Deletion of Tet2 in mice led to dramatic reduction in the 5-hydroxymethylcytosine levels and concomitant increase in the 5-methylcytosine levels in the genomic DNA of BM cells. The Tet2(-/-) mice contained an increased Lin(-)Sca-1(+)c-Kit(+) (LSK) cell pool before the development of myeloid malignancies. A competitive reconstitution assay revealed that Tet2(-/-) LSK cells had an increased hematopoietic repopulating capacity with an altered cell differentiation skewing toward monocytic/granulocytic lineages. Approximately 1/3 of Tet2(-/-) and 8% of Tet2(+/-) mice died within 1 year of age because of the development of myeloid malignancies resembling characteristics of CMML, MPD-like myeloid leukemia, and MDS. Furthermore, transplantation of Tet2(-/-), but not wild-type (WT) or Tet2(+/-) BM cells, led to increased WBC counts, monocytosis, and splenomegaly in WT recipient mice. These data indicate that Tet2-deficient mice recapitulate patients with myeloid malignancies, implying that Tet2 functions as a tumor suppressor to maintain hematopoietic cell homeostasis.
 ...
PMID:Deletion of Tet2 in mice leads to dysregulated hematopoietic stem cells and subsequent development of myeloid malignancies. 2203 42

This study was aimed to explore whether multiple common gene mutations of leukemia synergistically involved in acute promyelocytic leukemia (APL) pathogenesis, and to investigate their relevance to clinical features, cytogenetics and molecular risk stratification. 84 specimens of admitted de novo APL patients from February 2005 to October 2010 were collected, the gene mutations of bone marrow mononuclear cells and clinical features of mutation-positive patients were analyzed by genomic DNA-PCR. The results indicated that the prevalence of mutations was 60.7% (51/84), in which the mutations with the highest incidence were found as FLT3-ITD, reaching 27.4% (23/84). Next, there were 12 cases WT1 mutation, 9 for FLT3-TKD, 7 for TET2, 5 for N-RAS, 4 for ASXL1, 2 for EZH2 mutation and 1 positive case in MLL-PTD, IDH1 and CBL mutation respectively. No mutation was found in other JAK1, DNMT3, c-Kit, NPM1, IDH2, RUNX1 and JAK2 (V617F) common leukemia-related genes. Combined analysis with clinical data demonstrated that the patients with FLT3-ITD mutation displayed higher white blood cell counts, while the patients with N-RAS mutation showed lower platelet counts. Overall survival of these patients was obviously shorten as compared with patients with wild-type. This difference between mutant and wild-type of all above mentioned cases was statistically significant (P < 0.05). The difference between APL with simple t (15;17) and additional abnormal karyotype was not statistically significant. It is concluded that the FLT3-ITD mutation is recurrent genetic change in APL, and together with N-RAS mutation indicates poor prognosis. Additional abnormal karyotype does not associate with prognosis of APL.
 ...
PMID:[Clinical significance of common leukemia gene mutations in patients with acute promyelocytic leukemia]. 2348 88

Myeloproliferative neoplasms (MPNs) are clinically characterized by the chronic overproduction of differentiated peripheral blood cells and the gradual expansion of malignant intramedullary/extramedullary hematopoiesis. In MPNs mutations in JAK2 MPL or CALR are detected mutually exclusive in more than 90% of cases [1,2]. Mutations in them lead to the abnormal activation of JAK/STAT signaling and the autonomous growth of differentiated cells therefore they are considered as "driver" gene mutations. In addition to the above driver gene mutations mutations in epigenetic regulators such as TET2 DNMT3A ASXL1 EZH2 or IDH1/2 are detected in about 5%-30% of cases respectively [3]. Mutations in TET2 DNMT3A EZH2 or IDH1/2 commonly confer the increased self-renewal capacity on normal hematopoietic stem cells (HSCs) but they do not lead to the autonomous growth of differentiated cells and only exhibit subtle clinical phenotypes [4,6-8,5]. It was unclear how mutations in such epigenetic regulators influenced abnormal HSCs with driver gene mutations how they influenced the disease phenotype or whether a single driver gene mutation was sufficient for the initiation of human MPNs. Therefore we focused on JAK2V617F and loss of TET2-the former as a representative of driver gene mutations and the latter as a representative of mutations in epigenetic regulators-and examined the influence of single or double mutations on HSCs (Lineage(-)Sca-1(+)c-Kit(+) cells (LSKs)) by functional analyses and microarray whole-genome expression analyses [9]. Gene expression profiling showed that the HSC fingerprint genes [10] was statistically equally enriched in TET2-knockdown-LSKs but negatively enriched in JAK2V617F-LSKs compared to that in wild-type-LSKs. Double-mutant-LSKs showed the same tendency as JAK2V617F-LSKs in terms of their HSC fingerprint genes but the expression of individual genes differed between the two groups. Among 245 HSC fingerprint genes 100 were more highly expressed in double-mutant-LSKs than in JAK2V617F-LSKs. These altered gene expressions might partly explain the mechanisms of initiation and progression of MPNs which was observed in the functional analyses [9]. Here we describe gene expression profiles deposited at the Gene Expression Omnibus (GEO) under the accession number GSE62302 including experimental methods and quality control analyses.
...
PMID:Gene expression profiling of loss of TET2 and/or JAK2V617F mutant hematopoietic stem cells from mouse models of myeloproliferative neoplasms. 2648 91

TET2 is a dioxygenase that catalyses multiple steps of 5-methylcytosine oxidation. Although TET2 mutations frequently occur in various types of haematological malignancies, the mechanism by which they increase risk for these cancers remains poorly understood. Here we show that Tet2-/- mice develop spontaneous myeloid, T- and B-cell malignancies after long latencies. Exome sequencing of Tet2-/- tumours reveals accumulation of numerous mutations, including Apc, Nf1, Flt3, Cbl, Notch1 and Mll2, which are recurrently deleted/mutated in human haematological malignancies. Single-cell-targeted sequencing of wild-type and premalignant Tet2-/- Lin-c-Kit+ cells shows higher mutation frequencies in Tet2-/- cells. We further show that the increased mutational burden is particularly high at genomic sites that gained 5-hydroxymethylcytosine, where TET2 normally binds. Furthermore, TET2-mutated myeloid malignancy patients have significantly more mutational events than patients with wild-type TET2. Thus, Tet2 loss leads to hypermutagenicity in haematopoietic stem/progenitor cells, suggesting a novel TET2 loss-mediated mechanism of haematological malignancy pathogenesis.
 ...
PMID:Tet2 loss leads to hypermutagenicity in haematopoietic stem/progenitor cells. 2844 Mar 15

Myelodysplastic syndromes (MDSs) are clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis. Anemia is the defining cytopenia of MDS patients, yet the molecular mechanisms for dyserythropoiesis in MDSs remain to be fully defined. Recent studies have revealed that heterozygous loss-of-function mutation of DNA dioxygenase TET2 is 1 of the most common mutations in MDSs and that TET2 deficiency disturbs erythroid differentiation. However, mechanistic insights into the role of TET2 on disordered erythropoiesis are not fully defined. Here, we show that TET2 deficiency leads initially to stem cell factor (SCF)-dependent hyperproliferation and impaired differentiation of human colony-forming unit-erythroid (CFU-E) cells, which were reversed by a c-Kit inhibitor. We further show that this was due to increased phosphorylation of c-Kit accompanied by decreased expression of phosphatase SHP-1, a negative regulator of c-Kit. At later stages, TET2 deficiency led to an accumulation of a progenitor population, which expressed surface markers characteristic of normal CFU-E cells but were functionally different. In contrast to normal CFU-E cells that require only erythropoietin (EPO) for proliferation, these abnormal progenitors required SCF and EPO and exhibited impaired differentiation. We termed this population of progenitors "marker CFU-E" cells. We further show that AXL expression was increased in marker CFU-E cells and that the increased AXL expression led to increased activation of AKT and ERK. Moreover, the altered proliferation and differentiation of marker CFU-E cells were partially rescued by an AXL inhibitor. Our findings document an important role for TET2 in erythropoiesis and have uncovered previously unknown mechanisms by which deficiency of TET2 contributes to ineffective erythropoiesis.
 ...
PMID:TET2 deficiency leads to stem cell factor-dependent clonal expansion of dysfunctional erythroid progenitors. 3049 69