Abstract 16189: Histone Acetylation is Not Required for Reactivation of ANP and BNP in Human Heart Failure
Background: In heart failure, reactivation of a fetal gene program including atrial and brain natriuretic peptides (ANP and BNP) is a hallmark of left ventricular (LV) remodelling. The mechanisms that regulate this reactivation, however, are incompletely understood. Histone acetylation and methylation have a critical impact on the conformation of chromatin, which in turn governs the accessibility of DNA for transcription factors. Here, we analyze this “histone code” in the promotor regions of ANP and BNP in human failing (n=16) and nonfailing myocardium (NF; n=8) in relation to gene expression and regulatory factors.
Methods: Gene expression of ANP and BNP, but also methyltransferases G9a and SUV39H1 and demethylases LSD1 and JMJD1/2 were analyzed by real-time PCR. Western blot analysis of histone deacetylase 4 (HDAC4) was performed in nuclear and cytosolic protein fractions. Histone acetylation and methylation were analyzed by chromatin immunoprecipitation.
Results: ANP and BNP were 26- and 10-fold upregulated in failing vs. NF myocardium, respectively. This increase correlated with an overall ∼4-fold nuclear export of HDAC4 in failing vs. NF myocardium (r=0.60/0.61, p<0.01). Despite nuclear export of HDAC4, however, acetylation of histone 3 at lysines 9 and 27 (H3K9 and H3K27) and H4K91 in the promotor regions of ANP and BNP were either unchanged (H3K9, H4K91) or only modestly increased (H3K27) in failing myocardium. In contrast, di- and trimethylation of H3K9, indicating closed chromatin in the respective promotor regions, were consistently reduced by ∼40% in failing myocardium (p<0.05). H3K9 demethylation was associated with 2- to 3-fold upregulation of H3K9-specific demethylases JMJD1A and JMJD2A/B in failing hearts. Upregulation of JMJD1A correlated positively with ANP and BNP gene expression, but inversely with H3K9 methylation (all p<0.01). In contrast, expression of G9a, SUV39H1 and LSD1 were unchanged in failing vs. NF myocardium.
Conclusions: In human heart failure, the reactivation of ANP and BNP is associated with a distinct pattern of histone modifications, governed primarily by histone demethylation at H3K9. In contrast, increased histone acetylation in the promoter regions of these genes is not required for their reactivation.
- © 2010 by American Heart Association, Inc.