The SCL +40 enhancer targets the midbrain together with primitive and definitive hematopoiesis and is regulated by SCL and GATA proteins.
The SCL/Tal-1 gene encodes a basic helix-loop-helix transcription factor with key roles in hematopoietic and neural development. SCL is expressed in, and required for, both primitive and definitive erythropoiesis. Thus far, we have identified only one erythroid SCL enhancer. Located 40 kb downstream of exon 1a, the +40 enhancer displays activity in primitive erythroblasts. We demonstrate here that a 3.7-kb fragment containing this element also targets expression to the midbrain, a known site of endogenous SCL expression. Although the 3.7-kb construct was active in primitive, but not definitive, erythroblasts, a larger 5.0-kb fragment, encompassing the 3.7-kb region, was active in both fetal and adult definitive hematopoietic cells. This included Ter119+ erythroid cells along with fetal liver erythroid and myeloid progenitors. Unlike two other SCL hematopoietic enhancers (+18/19 and -4), +40 enhancer transgenes were inactive in the endothelium. A conserved 400-bp core region, essential for both hematopoietic and midbrain +40 enhancer activity in embryos, relied on two GATA/E-box motifs and was bound in vivo by GATA-1 and SCL in erythroid cells. These results suggest a model in which the SCL +18/19 and/or -4 enhancers initiate SCL expression in early mesodermal derivatives capable of generating blood and endothelium, with subsequent activation of the +40 enhancer via an autoregulatory loop.
Ogilvy
S
S
Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, United Kingdom.
Ferreira
R
R
Piltz
S G
SG
Bowen
J M
JM
Göttgens
B
B
Green
A R
AR
D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001854:Bone Marrow Cells / Q000502:physiology; D004622:Embryo, Mammalian / Q000033:anatomy & histology / Q000502:physiology; D004742:Enhancer Elements, Genetic; D050980:GATA Transcription Factors / Q000235:genetics / Q000378:metabolism*; D006410:Hematopoiesis / Q000502:physiology*; D006801:Humans; D008099:Liver / Q000166:cytology / Q000196:embryology / Q000502:physiology; D008636:Mesencephalon / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017385:Sequence Homology; D013234:Stem Cells / Q000502:physiology; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D019076:Transgenes
D051792:Basic Helix-Loop-Helix Proteins; D050980:GATA Transcription Factors; D011518:Proto-Oncogene Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; C489366:Tal1 protein, mouse
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