RESUMO
Analysis of cis-regulatory elements is central to understanding the genomic program for development. The scl/tal-1 transcription factor is essential for lineage commitment to blood cell formation and previous studies identified an scl enhancer (the +18/19 element) which was sufficient to target the vast majority of hematopoietic stem cells, together with hematopoietic progenitors and endothelium. Moreover, expression of scl under control of the +18/19 enhancer rescued blood progenitor formation in scl(-/-) embryos. However, here we demonstrate by using a knockout approach that, within the endogenous scl locus, the +18/19 enhancer is not necessary for the initiation of scl transcription or for the formation of hematopoietic cells. These results led to the identification of a bifunctional 5' enhancer (-3.8 element), which targets expression to hematopoietic progenitors and endothelium, contains conserved critical Ets sites, and is bound by Ets family transcription factors, including Fli-1 and Elf-1. These data demonstrate that two geographically distinct but functionally related enhancers regulate scl transcription in hematopoietic progenitors and endothelial cells and suggest that enhancers with dual hematopoietic-endothelial activity may represent a general strategy for regulating blood and endothelial development.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Elementos Facilitadores Genéticos , Hematopoese/fisiologia , Células-Tronco Hematopoéticas/fisiologia , Proteínas Proto-Oncogênicas/metabolismo , Fatores de Transcrição/metabolismo , Animais , Sequência de Bases , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Linhagem da Célula , Proteínas de Ligação a DNA/genética , Embrião de Mamíferos/anatomia & histologia , Embrião de Mamíferos/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Genes Reporter , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Dados de Sequência Molecular , Proteínas Nucleares , Proteína Proto-Oncogênica c-fli-1 , Proteínas Proto-Oncogênicas/genética , Alinhamento de Sequência , Proteína 1 de Leucemia Linfocítica Aguda de Células T , Transativadores/metabolismo , Fatores de Transcrição/genética , Transcrição GênicaAssuntos
Meio Ambiente , Nível de Saúde , Estilo de Vida , Doença Pulmonar Obstrutiva Crônica , Telemedicina , Adulto , Idoso , Estudos de Coortes , DNA , Feminino , Interação Gene-Ambiente , Predisposição Genética para Doença , Humanos , Masculino , Pessoa de Meia-Idade , Fumar , Meio Social , Reino UnidoRESUMO
The stem cell leukemia (SCL) gene encodes a bHLH transcription factor with a pivotal role in hematopoiesis and vasculogenesis and a pattern of expression that is highly conserved between mammals and zebrafish. Here we report the isolation and characterization of the zebrafish SCL locus together with the identification of three neighboring genes, IER5, MAP17, and MUPP1. This region spans 68 kb and comprises the longest zebrafish genomic sequence currently available for comparison with mammalian, chicken, and pufferfish sequences. Our data show conserved synteny between zebrafish and mammalian SCL and MAP17 loci, thus suggesting the likely genomic domain necessary for the conserved pattern of SCL expression. Long-range comparative sequence analysis/phylogenetic footprinting was used to identify noncoding conserved sequences representing candidate transcriptional regulatory elements. The SCL promoter/enhancer, exon 1, and the poly(A) region were highly conserved, but no homology to other known mouse SCL enhancers was detected in the zebrafish sequence. A combined homology/structure analysis of the poly(A) region predicted consistent structural features, suggesting a conserved functional role in mRNA regulation. Analysis of the SCL promoter/enhancer revealed five motifs, which were conserved from zebrafish to mammals, and each of which is essential for the appropriate pattern or level of SCL transcription.