T-box binding sites are required for activity of a cardiac GATA-4 enhancer.
GATA-4 is a key regulator of a poorly understood cardiac morphogenetic program. We used genomic regions of the GATA-4 gene to target GFP expression to the developing heart of living fish. In these fish, GFP-expressing cells in the lateral plate mesoderm form two tubes that migrate ventrally to fuse into a linear heart tube. In addition, we find that a 14.8-kb fragment upstream of the transcription initiation site targets expression to both chambers and the valves of the heart. Truncation of 7 kb of the distal sequences eliminates expression in the atrium and the atrioventricular valve while expression is retained in the ventricle and the bulboventricular valve. Within this 7-kb distal regulatory region, we delineated a 1300-bp region with a cluster of consensus binding sites for T-box transcription factors. Mutation of these sequences significantly reduces reporter gene expression in the heart. This provides the first evidence that T-box factors function by directly regulating GATA-4 expression. Thus, GATA-4 regulatory elements control gene expression differentially along the rostro-caudal axis, and T-box binding elements in the GATA-4 promoter contribute to heart-specific expression.
Heicklen-Klein
Alice
A
Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Evans
Todd
T
D000818:Animals; D030801:Animals, Genetically Modified; D015139:Blotting, Southern; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D050991:GATA4 Transcription Factor; D040461:Gene Components; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins; D006321:Heart / Q000196:embryology*; D017403:In Situ Hybridization; D008164:Luminescent Proteins / Q000378:metabolism; D008845:Microinjections; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000235:genetics; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D015027:Zebrafish
D017931:DNA Primers; D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D008164:Luminescent Proteins; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins