Childhood Leukemia Research Institute

Ramat Gan, Israel

Childhood Leukemia Research Institute

Ramat Gan, Israel
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Shaham L.,Childhood Leukemia Research Institute | Shaham L.,Bar - Ilan University | Vendramini E.,Childhood Leukemia Research Institute | Vendramini E.,Tel Aviv University | And 20 more authors.
Blood | Year: 2015

Children with Down syndrome (DS) are at increased risk for acute myeloid leukemias (ML-DS) characterized bymixedmegakaryocytic and erythroid phenotype and by acquired mutations in the GATA1 gene resulting in a short GATA1s isoform. The chromosome 21 microRNA (miR)-125b cluster has been previously shown to cooperate with GATA1s in transformation of fetal hematopoietic progenitors. In this study, we report that the expression of miR-486-5p is increased in ML-DS compared with non-DS acute megakaryocytic leukemias (AMKLs). miR-486-5p is regulated by GATA1 and GATA1s that bind to the promoter of its host gene ANK1. miR-486-5p is highly expressed in mouse erythroid precursors and knockdown (KD) inML-DS cells reduced their erythroid phenotype. Ectopic expression and KD of miR-486-5p in primary fetal liver hematopoietic progenitors demonstrated that miR-486-5pcooperateswithGata1s to enhance their self renewal.Consistent with its activation of AKT, overexpression and KD experiments showed its importance for growth and survival of human leukemic cells. Thus, miR-486-5p cooperates withGATA1s in supporting the growth and survival, and the aberrant erythroid phenotype of the megakaryocytic leukemias of DS. © 2015 by The American Society of Hematology.


Shochat C.,Childhood Leukemia Research Institute | Shochat C.,Migal Galilee Bio Technology Center | Shochat C.,Tel Aviv University | Shochat C.,Tel-Hai Academic College | And 22 more authors.
Journal of Experimental Medicine | Year: 2011

Interleukin-7 receptor α (IL7R) is required for normal lymphoid development. Loss-offunction mutations in this gene cause autosomal recessive severe combined immune deficiency. Here, we describe somatic gain-of-function mutations in IL7R in pediatric B and T acute lymphoblastic leukemias. The mutations cause either a serine-to-cysteine substitution at amino acid 185 in the extracellular domain (4 patients) or in-frame insertions and deletions in the transmembrane domain (35 patients). In B cell precursor leukemias, the mutations were associated with the aberrant expression of cytokine receptor-like factor 2 (CRLF2), and the mutant IL-7R proteins formed a functional receptor with CRLF2 for thymic stromal lymphopoietin (TSLP). Biochemical and functional assays reveal that these IL7R mutations are activating mutations conferring cytokine-independent growth of progenitor lymphoid cells. A cysteine, included in all but three of the mutated IL-7R alleles, is essential for the constitutive activation of the receptor. This is the first demonstration of gain-of-function mutations of IL7R. Our current and recent observations of mutations in IL7R and CRLF2, respectively suggest that the addition of cysteine to the juxtamembranous domains is a general mechanism for mutational activation of type I cytokine receptors in leukemia. © 2011 by The Rockefeller University Press.

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