title: Incomplete splicing, cell division defects, and hematopoietic blockage in dhx8 mutant zebrafish.
abstract: BACKGROUND
  Vertebrate hematopoiesis is a complex developmental process that is controlled by genes in diverse pathways. To identify novel genes involved in early hematopoiesis, we conducted an ENU (N-ethyl-N-nitrosourea) mutagenesis screen in zebrafish. The mummy (mmy) line was investigated because of its multiple hematopoietic defects.
  
  
  RESULTS
  Homozygous mmy embryos lacked circulating blood cell types and were dead by 30 hr post-fertilization (hpf). The mmy mutants did not express myeloid markers and had significantly decreased expression of progenitor and erythroid markers in primitive hematopoiesis. Through positional cloning, we identified a truncation mutation in dhx8 in the mmy fish. dhx8 is the zebrafish ortholog of the yeast splicing factor prp22, which is a DEAH-box RNA helicase. mmy mutants had splicing defects in many genes, including several hematopoietic genes. mmy embryos also showed cell division defects as characterized by disorganized mitotic spindles and formation of multiple spindle poles in mitotic cells. These cell division defects were confirmed by DHX8 knockdown in HeLa cells.
  
  
  CONCLUSIONS
  Together, our results confirm that dhx8 is involved in mRNA splicing and suggest that it is also important for cell division during mitosis. This is the first vertebrate model for dhx8, whose function is essential for primitive hematopoiesis in developing embryos.
authors.affiliation: Oncogenesis and Development Section, National Human Genome Research Institute/NIH, Bethesda, MD 20892, USA.
authors.forename: Milton A
authors.initials: MA
authors.lastname: English
authors.forename: Lin
authors.initials: L
authors.lastname: Lei
authors.forename: Trevor
authors.initials: T
authors.lastname: Blake
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Wincovitch
authors.forename: Raman
authors.initials: R
authors.lastname: Sood
authors.forename: Mizuki
authors.initials: M
authors.lastname: Azuma
authors.forename: Dennis
authors.initials: D
authors.lastname: Hickstein
authors.forename: P Paul
authors.initials: PP
authors.lastname: Liu
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division / Q000235:genetics*; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism; D006410:Hematopoiesis / Q000235:genetics*; D006413:Hematopoietic System / Q000378:metabolism; D012326:RNA Splicing / Q000235:genetics*; D015027:Zebrafish / Q000235:genetics* / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D029961:Zebrafish Proteins; C574992:DHX8 protein, zebrafish; D053487:DEAD-box RNA Helicases