Abstract 13886: Gata4 Expression is Regulated, Primarily, via a Phospholipase C Beta1-miR-26-Dependent Posttranscriptional Mechanism During Cardiac Hypertrophy
GATA4 plays an essential role in the development of cardiac hypertrophy, however, its mode of regulation remains unknown. In this study we investigated transcriptional vs. posttranscriptional mechanisms that are involved in regulating GATA4 in the heart during neonatal and pressure-induced hypertrophic growth. Our data show that GATA4 gene translation is significantly higher during neonatal (6.8 ± 1 fold) and pressure overload-induced (2.9 ± 0.4 fold) cardiac hypertrophy vs. a sham-operated or normal adult mouse heart, compared to its transcription, as measured by RNA polymerase II chromatin immunoprecipitation-deep sequencing (2 and 0.97 fold, respectively), or mRNA levels (1.6 ± 0.4 and 1.1 ± 0.15 fold, respectively), which suggests mainly a posttranscriptional mode of regulation during pressure-induced hypertrophy. The 3’UTR of GATA4 harbors conserved miRNA target sites. Of those, only miR-26 inversely correlates with GATA4 expression during neonatal and pressure overload-induced hypertrophy. Indeed, deletion of the miR-26 site results in ~ 2x increase in GATA4 protein in cardiac myocytes, whereas modulation of the miR-26 levels inversely impacts GATA4 levels. In addition, supplying cardiac myocytes with exogenous miR-26 inhibits GATA4-dependent transcription, endothelin-induced hypertrophy, and sensitizes the cells to apoptotic insults. We also found that miR-26 targets phospholipase C-beta1 (PLCβ1), which through a negative feedback loop inhibits the expression of miR-26. Ultimately, we questioned whether reducing miR-26 in the adult heart is indeed sufficient for inducing upregulation of GATA4 and PLCβ1. For that purpose we injected locked-nucleic acid-modified antisense miR-26a intravenously. This treatment resulted in very effective downregulation of miR-26, which was accompanied by the upregulation of both its targets within 7 days to the same extent observed during hypertrophy. Although, this was not accompanied by an increase in heart/body weight at this time point, it did induced upregulation of, at least, atrial natriuretic factor and skeletal-alpha-actin. From these results we conclude that GATA4 expression is mainly regulated by a PLCβ1-miR-26-dependent mechanism during pathological hypertrophy.
- © 2011 by American Heart Association, Inc.