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Ddx18 is essential for cell-cycle progression in zebrafish hematopoietic cells and is mutated in human AML.

In a zebrafish mutagenesis screen to identify genes essential for myelopoiesis, we identified an insertional allele hi1727, which disrupts the gene encoding RNA helicase dead-box 18 (Ddx18). Homozygous Ddx18 mutant embryos exhibit a profound loss of myeloid and erythroid cells along with cardiovascular abnormalities and reduced size. These mutants also display prominent apoptosis and a G1 cell-cycle arrest. Loss of p53, but not Bcl-xl overexpression, rescues myeloid cells to normal levels, suggesting that the hematopoietic defect is because of p53-dependent G1 cell-cycle arrest. We then sequenced primary samples from 262 patients with myeloid malignancies because genes essential for myelopoiesis are often mutated in human leukemias. We identified 4 nonsynonymous sequence variants (NSVs) of DDX18 in acute myeloid leukemia (AML) patient samples. RNA encoding wild-type DDX18 and 3 NSVs rescued the hematopoietic defect, indicating normal DDX18 activity. RNA encoding one mutation, DDX18-E76del, was unable to rescue hematopoiesis, and resulted in reduced myeloid cell numbers in ddx18(hi1727/+) embryos, indicating this NSV likely functions as a dominant-negative allele. These studies demonstrate the use of the zebrafish as a robust in vivo system for assessing the function of genes mutated in AML, which will become increasingly important as more sequence variants are identified by next-generation resequencing technologies.

Pubmed ID: 21653321

Authors

  • Payne EM
  • Bolli N
  • Rhodes J
  • Abdel-Wahab OI
  • Levine R
  • Hedvat CV
  • Stone R
  • Khanna-Gupta A
  • Sun H
  • Kanki JP
  • Gazda HT
  • Beggs AH
  • Cotter FE
  • Look AT

Journal

Blood

Publication Data

July 28, 2011

Associated Grants

  • Agency: NCI NIH HHS, Id: 5T32 CA009382-26

Mesh Terms

  • Alleles
  • Animals
  • Blotting, Western
  • Cell Cycle
  • Cell Separation
  • DEAD-box RNA Helicases
  • Embryo, Nonmammalian
  • Flow Cytometry
  • Hematopoiesis
  • Hematopoietic Stem Cells
  • Humans
  • In Situ Hybridization
  • Leukemia, Myeloid, Acute
  • Mutagenesis, Site-Directed
  • Mutation
  • Myeloid Cells
  • Polymerase Chain Reaction
  • Zebrafish
  • Zebrafish Proteins