GATA4 expression is primarily regulated via a miR-26b-dependent post-transcriptional mechanism during cardiac hypertrophy.
OBJECTIVE
GATA4 is a transcription factor that is up-regulated during cardiac hypertrophy and plays a fundamental role in myocyte growth and survival. In this study, we investigate the transcriptional vs. post-transcriptional mechanisms that are involved in regulating GATA4 in the heart during neonatal and pressure overload-induced hypertrophic growth.


RESULTS
GATA4 protein is significantly higher during pressure overload-induced (2.9 ± 0.4-fold) and neonatal (6.8 ± 1-fold) hypertrophic growth vs. the normal adult mouse heart. Using RNA polymerase II immunoprecipitation combined with deep sequencing, we confirmed that active transcription of the Gata4 gene remained unchanged during hypertrophy, whereas it was two-fold higher in the neonatal vs. adult heart, commensurate with the mRNA levels. These results suggested a post-transcriptional mode of regulation of its expression, which prompted the identification of a conserved sequence in its 3'-untranslated region that was responsible for reduced translation via miR-26b. Overexpression of miR-26b reduced GATA4-dependent transcription, endothelin-induced hypertrophy, and sensitized the cells to apoptotic insults. Additionally, miR-26b targeted phospholipase C-β1, which, in turn, inhibited miR-26b expression, creating a double-negative feedback loop. Accordingly, overexpression of miR-26b in the heart inhibited up-regulation of its targets and the development of hypertrophy. However, knockdown of miR-26b is not sufficient for inducing hypertrophy.


CONCLUSIONS
Down-regulation of miR-26b in the heart is required for the up-regulation of GATA4 and the induction of pressure-induced cardiac hypertrophy. The results also underscore the functional relevance of miRNAs in regulating gene expression during cardiac hypertrophy.
Department of Cell Biology and Molecular Medicine,  Cardiovascular Research Institute, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103,  USA.
Mingyue
M
Han
Zhi
Z
Yang
Danish
D
Sayed
Minzhen
M
He
Shumin
S
Gao
Lin
L
Lin
Seonghun
S
Yoon
Maha
M
Abdellatif
D000818:Animals; D006332:Cardiomegaly / Q000378:metabolism* / Q000503:physiopathology*; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology; D050991:GATA4 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics / Q000502:physiology*; D054799:Phospholipase C beta / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology
D050991:GATA4 Transcription Factor; C484171:Gata4 protein, mouse; D035683:MicroRNAs; C543693:Mirn26 microRNA, mouse; D054799:Phospholipase C beta