Subject(s)
Environment , Health Status , Life Style , Pulmonary Disease, Chronic Obstructive , Telemedicine , Adult , Aged , Cohort Studies , DNA , Female , Gene-Environment Interaction , Genetic Predisposition to Disease , Humans , Male , Middle Aged , Smoking , Social Environment , United KingdomABSTRACT
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.
Subject(s)
DNA-Binding Proteins/metabolism , Enhancer Elements, Genetic , Hematopoiesis/physiology , Hematopoietic Stem Cells/physiology , Proto-Oncogene Proteins/metabolism , Transcription Factors/metabolism , Animals , Base Sequence , Basic Helix-Loop-Helix Transcription Factors , Cell Lineage , DNA-Binding Proteins/genetics , Embryo, Mammalian/anatomy & histology , Embryo, Mammalian/physiology , Gene Expression Regulation, Developmental , Genes, Reporter , Humans , Mice , Mice, Inbred C57BL , Mice, Knockout , Molecular Sequence Data , Nuclear Proteins , Proto-Oncogene Protein c-fli-1 , Proto-Oncogene Proteins/genetics , Sequence Alignment , T-Cell Acute Lymphocytic Leukemia Protein 1 , Trans-Activators/metabolism , Transcription Factors/genetics , Transcription, GeneticABSTRACT
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.