Direct activation of a GATA6 cardiac enhancer by Nkx2.5: evidence for a reinforcing regulatory network of Nkx2.5 and GATA transcription factors in the developing heart.
The zinc finger transcription factors GATA4, -5, and -6 and the homeodomain protein Nkx2.5 are expressed in the developing heart and have been shown to activate a variety of cardiac-specific genes. To begin to define the regulatory relationships between these cardiac transcription factors and to understand the mechanisms that control their expression during cardiogenesis, we analyzed the mouse GATA6 gene for regulatory elements sufficient to direct cardiac expression during embryogenesis. Using beta-galactosidase fusion constructs in transgenic mice, a 4.3-kb 5' regulatory region that directed transcription specifically in the cardiac lineage, beginning at the cardiac crescent stage, was identified. Thereafter, transgene expression became compartmentalized to the outflow tract, a portion of the right ventricle, and a limited region of the common atrial chamber of the embryonic heart. Further dissection of this regulatory region identified a 1.8-kb cardiac-specific enhancer that recapitulated the expression pattern of the larger region when fused to a heterologous promoter and a smaller 500-bp subregion that retained cardiac expression, but was quantitatively weaker. The GATA6 cardiac enhancer contained a binding site for Nkx2.5 that was essential for cardiac-specific expression in transgenic mice. These studies demonstrate that GATA6 is a direct target gene for Nkx2.5 in the developing heart and reveal a mutually reinforcing regulatory network of Nkx2.5 and GATA transcription factors during cardiogenesis.
Molkentin
J D
JD
Division of Molecular Cardiovascular Biology, Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, Ohio, 45229-3039, USA. molkj0@chmcc.org
Antos
C
C
Mercer
B
B
Taigen
T
T
Miano
J M
JM
Olson
E N
EN
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019070:Cell Lineage; D004268:DNA-Binding Proteins / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D050993:GATA6 Transcription Factor; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation; D029867:Xenopus Proteins
D004268:DNA-Binding Proteins; D050993:GATA6 Transcription Factor; C494760:Gata6 protein, mouse; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D014157:Transcription Factors; D029867:Xenopus Proteins