title: The Hox cofactors Meis1 and Pbx act upstream of gata1 to regulate primitive hematopoiesis.
abstract: During vertebrate development, the initial wave of hematopoiesis produces cells that help to shape the developing circulatory system and oxygenate the early embryo. The differentiation of primitive erythroid and myeloid cells occurs within a short transitory period, and is subject to precise molecular regulation by a hierarchical cascade of transcription factors. The TALE-class homeodomain transcription factors Meis and Pbx function to regulate embryonic hematopoiesis, but it is not known where Meis and Pbx proteins participate in the hematopoietic transcription factor cascade. To address these questions, we have ablated Meis1 and Pbx proteins in zebrafish, and characterized their molecular effects on known markers of primitive hematopoiesis. Embryos lacking Meis1 and Pbx exhibit a severe reduction in the expression of gata1, the earliest marker of erythroid cell fate, and fail to produce visible circulating blood cells. Concomitant with a loss of gata1, Meis1- and Pbx-depleted embryos exhibit downregulated embryonic hemoglobin (hbae3) expression, and possess increased numbers of pu.1-positive myeloid cells. gata1-overexpression rescues hbae3 expression in Pbx-depleted; meis1-morphant embryos, placing Pbx and Meis1 upstream of gata1 in the erythropoietic transcription factor hierarchy. Our study conclusively demonstrates that Meis1 and Pbx act to specify the erythropoietic cell lineage and inhibit myelopoiesis.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Pillay
authors.forename: A Michael
authors.initials: AM
authors.lastname: Forrester
authors.forename: Timothy
authors.initials: T
authors.lastname: Erickson
authors.forename: Jason N
authors.initials: JN
authors.lastname: Berman
authors.forename: Andrew Jan
authors.initials: AJ
authors.lastname: Waskiewicz
mesh_terms: D000818:Animals; D019070:Cell Lineage / Q000235:genetics; D004625:Embryo, Nonmammalian; D015672:Erythroid Precursor Cells / Q000166:cytology; D004920:Erythropoiesis / Q000235:genetics; D050982:GATA1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006410:Hematopoiesis / Q000235:genetics*; D006651:Histocytochemistry; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D038042:Myelopoiesis / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D050982:GATA1 Transcription Factor; D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D014157:Transcription Factors; D029961:Zebrafish Proteins; C494691:gata1a protein, zebrafish