title: The role of jak2a in zebrafish hematopoiesis.
abstract: Janus kinase 2 (Jak2) transduces signals from hematopoietic cytokines, and a gain-of-function mutation (Jak2(617V>F)) is associated with myeloproliferative diseases, particularly polycythemia vera. In this study, we examined the role of jak2a in zebrafish embryos in knock-down and overexpression studies using morpholinos (MOs) targeting the 5' untranslated region (UTR) (jak2a(UTR)-MO) and splice-site junction (jak2a(SS)-MO) of jak2a, a Jak inhibitor AG490 and a constitutive-active form of jak2a (jak2a(ca)). At 18 and 24 hours after fertilization (hpf), jak2a is expressed predominantly in the intermediate cell mass (ICM; site of primitive hematopoiesis) of wild-type and chordin morphant embryos (characterized by expansion of ICM). Both jak2a MOs and AG490 reduced gata1(+) (erythroid) cells in Tg(gata1:GFP) embryos, signal transducer and activation of transcription 5 (stat5) phosphorylation, and gene expression associated with early progenitors (scl and lmo2) and erythroid (gata1, alphahe1 and betahe1) and myeloid (spi1 [early] and mpo [late]) lineages. The chordin morphant is associated with increased stat5 phosphorylation, and both jak2a MOs and treatment with AG490 significantly ameliorated ICM expansion and hematopoietic gene up-regulation in these embryos. Injection of plasmid encoding jak2a(ca) significantly increased erythropoiesis and expression of gata1, alphahe1 and betahe1, spi1, mpo, and l-plastin. In conclusion, zebrafish jak2a is involved in primitive hematopoiesis under normal and deregulated conditions.
authors.affiliation: Department of Medicine, University of Hong Kong, Hong Kong, China.
authors.forename: Alvin C H
authors.initials: AC
authors.lastname: Ma
authors.forename: Alister C
authors.initials: AC
authors.lastname: Ward
authors.forename: Raymond
authors.initials: R
authors.lastname: Liang
authors.forename: Anskar Y H
authors.initials: AY
authors.lastname: Leung
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002455:Cell Division; D019070:Cell Lineage; D004625:Embryo, Nonmammalian / Q000502:physiology*; D004789:Enzyme Activation; D015672:Erythroid Precursor Cells / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D006023:Glycoproteins / Q000378:metabolism; D006410:Hematopoiesis; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D053614:Janus Kinase 2 / Q000235:genetics / Q000502:physiology*; D018919:Neovascularization, Physiologic; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D050799:STAT5 Transcription Factor; D029961:Zebrafish Proteins; C054234:chordin; D053614:Janus Kinase 2