A Conserved Stress-Inducible Hub Enhancer Governs Natriuretic Peptide Expression and Undergoes Dynamic and Reversible Activation in Human Heart Failure
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Background
Natriuretic peptides (NPs), encoded by the NPPA and NPPB genes, serve as both diagnostic biomarkers and cardioprotective hormones in heart failure. Their expression is tightly regulated by mechanical load, yet the upstream enhancer mechanisms translating hemodynamic stress into transcriptional activation remain incompletely understood.
Methods
We investigated the Nppa / Nppb super-enhancer (SE), which resides in a well-insulated topologically associating domain (TAD) and regulates stress-inducible expression of Nppa and Nppb . We applied CRISPR-based enhancer perturbation, chromatin accessibility and histone profiling, chromatin conformation assays, genetic mouse models, human iPSC-derived cardiomyocytes, and paired failing human hearts before and after left ventricular assist device (LVAD) unloading.
Results
Through integrative epigenomic and genetic analyses, we identified a conserved element, CR9, as a dominant hub enhancer within this SE. In neonatal rat cardiomyocytes, CRISPR-based activation and inhibition established that CR9 was both necessary and sufficient for NP induction, whereas neighboring elements (CR7/CR8) displayed modest activity but synergized with CR9, establishing a hierarchical and cooperative SE architecture. In vivo, CR9 deletion in mice markedly suppressed Nppa / Nppb expression and diminished chromatin accessibility and histone acetylation across adjacent enhancers and promoters, underscoring its structural as well as transcriptional role. Reinsertion of CR9, even in reverse orientation, restored transcription, confirming its orientation-independent activity. CR9 function remained confined within TAD boundaries, supporting a locus-specific regulation. RNAscope revealed spatial proximity between CR9 enhancer RNA and Nppa / Nppb nascent transcripts. Developmental profiling revealed a switch in enhancer usage from CR6/CR7 in the fetal heart to CR9 in adulthood, indicating a transition from developmental to stress-inducible regulation. In human induced pluripotent stem cell–derived cardiomyocytes, deletion of CR9 nearly abolished NPPA / NPPB expression, establishing its essential role in a human cellular context. Most notably, in paired human failing hearts before and after LVAD unloading, chromatin accessibility at CR9 was dynamically reversed, providing the first direct evidence that enhancer states are plastic and therapeutically modifiable in the human myocardium.
Conclusions
CR9 functions as a stress-inducible hub enhancer that coordinates NP transcription under pathological load. This enhancer exhibits reversible activation in human hearts, underscoring enhancer plasticity as a modifiable regulatory layer mediating stress-responsive transcriptional adaptation in the diseased myocardium.
Clinical Perspective
What is new?
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We identified CR9 as a stress-inducible hub enhancer within the Nppa / Nppb super-enhancer that is both necessary and sufficient for natriuretic peptide induction, defining a hierarchical and cooperative regulatory architecture controlling Nppa and Nppb expression.
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We uncovered a developmental switch in enhancer usage from CR6 in the fetal heart to CR9 in adulthood, revealing how stress-inducible enhancer activity emerges as the heart transitions from developmental to adaptive regulation.
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Using paired failing human hearts before and after LVAD unloading, we provide the first direct evidence that enhancer states are dynamically reversible in the human myocardium.
What are the clinical implications?
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The reversibility of CR9 activity in human heart failure provides a molecular basis for how natriuretic peptide levels decrease when cardiac function improves with effective therapy, reflecting the underlying enhancer plasticity of the diseasesd myocardium.
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Enhancer plasticity is an emerging and targetable mechanism in heart failure, raising the possibility that stress-inducible enhancers like CR9 could be engineered to switch on cardioprotective genes when the heart is under stress, offering a new strategy for precision gene therapy.
