NKX2-5 regulates the expression of beta-catenin and GATA4 in ventricular myocytes.
BACKGROUND
The molecular pathway that controls cardiogenesis is temporally and spatially regulated by master transcriptional regulators such as NKX2-5, Isl1, MEF2C, GATA4, and beta-catenin. The interplay between these factors and their downstream targets are not completely understood. Here, we studied regulation of beta-catenin and GATA4 by NKX2-5 in human fetal cardiac myocytes.


RESULTS
Using antisense inhibition we disrupted the expression of NKX2-5 and studied changes in expression of cardiac-associated genes. Down-regulation of NKX2-5 resulted in increased beta-catenin while GATA4 was decreased. We demonstrated that this regulation was conferred by binding of NKX2-5 to specific elements (NKEs) in the promoter region of the beta-catenin and GATA4 genes. Using promoter-luciferase reporter assay combined with mutational analysis of the NKEs we demonstrated that the identified NKX2-5 binding sites were essential for the suppression of beta-catenin, and upregulation of GATA4 by NKX2-5.


CONCLUSIONS
This study suggests that NKX2-5 modulates the beta-catenin and GATA4 transcriptional activities in developing human cardiac myocytes.
Riazi
Ali M
AM
Labatt Family Heart Centre, Hospital for Sick Children, Toronto, Ontario, Canada. ali.riazi@sickkids.ca
Takeuchi
Jun K
JK
Hornberger
Lisa K
LK
Zaidi
Syed Hassan
SH
Amini
Fariba
F
Coles
John
J
Bruneau
Benoit G
BG
Van Arsdell
Glen S
GS
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D050991:GATA4 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006352:Heart Ventricles / Q000166:cytology*; D006579:Heterozygote; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics*
D050991:GATA4 Transcription Factor; C484170:GATA4 protein, human; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D012333:RNA, Messenger; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin