HEY2 Represses Mitochondrial Respiration to Preserve Cardiac Function

Study Background and Research Question

Heart failure (HF) remains a leading cause of morbidity and mortality worldwide, with its pathophysiology closely tied to impaired mitochondrial energy metabolism in cardiomyocytes. A pivotal aspect of HF is the metabolic rewiring of cardiac cells: healthy adult hearts rely predominantly on mitochondrial fatty acid oxidation for ATP generation, but failing hearts shift toward glycolysis due to mitochondrial dysfunction. The molecular mechanisms balancing mitochondrial biogenesis and oxidative metabolism, and how these processes become dysregulated in HF, are not fully understood. The study by She et al. (Nature Communications, 2025) addresses this knowledge gap by interrogating the role of the transcriptional repressor HEY2 in regulating mitochondrial oxidative respiration and its contribution to cardiac homeostasis and disease.

Key Innovation from the Reference Study

This work identifies HEY2 as a direct, evolutionarily conserved repressor of mitochondrial oxidative metabolism genes in the heart. Unlike previous studies that focused on the activation of mitochondrial biogenesis factors, She et al. reveal that upregulation of HEY2 in human dilated cardiomyopathy and animal models leads to suppression of core metabolic genes, impaired mitochondrial function, and ultimately heart failure. Conversely, genetic depletion of Hey2 enhances mitochondrial gene expression and protects against cardiac dysfunction, positioning HEY2 as a potential molecular switch safeguarding the balance of cardiac energy metabolism. The study further elucidates the HEY2/HDAC1-Ppargc1/Cpt module as a regulatory axis controlling the transcriptional landscape of metabolic genes in cardiomyocytes.

Methods and Experimental Design Insights

• Patient and Animal Models: HEY2 expression was evaluated in human cardiac tissues from patients with dilated cardiomyopathy. Functional consequences of Hey2 induction or depletion were studied in zebrafish, mouse models, and cultured mammalian cardiomyocytes [paper].
• Mitochondrial Function Assays: Oxygen consumption rates and mitochondrial oxidative phosphorylation were assessed to determine the impact of HEY2 modulation on cellular energetics.
• Genome-wide Analyses: Chromatin immunoprecipitation sequencing (ChIP-seq) and transcriptomic profiling mapped HEY2 binding sites and downstream gene expression changes, identifying direct repression of metabolic regulators such as Ppargc1 (PGC-1), Esrra, and Cpt1.
• Rescue and Knockdown Experiments: Restoration of PPARGC1A/ESRRA in HEY2-overexpressing models, and targeted knockdown of Hey2 in adult mouse hearts, were performed to test the reversibility and specificity of the metabolic phenotype.

Core Findings and Why They Matter

The study provides compelling evidence that:

• HEY2 is upregulated in failing human hearts, and its induction in zebrafish or mammalian cardiomyocytes suppresses mitochondrial respiration and elevates reactive oxygen species (ROS), promoting cardiomyocyte apoptosis and heart failure [paper].
• HEY2 directly binds to promoters of mitochondrial oxidative metabolism genes—such as Ppargc1, Esrra, and Cpt1—and recruits HDAC1, resulting in histone deacetylation and robust transcriptional repression.
• Genetic depletion of Hey2 enhances expression of these metabolic genes, improves mitochondrial function, and protects against doxorubicin-induced cardiac dysfunction in mice [paper].
• Rescuing PPARGC1A/ESRRA expression in HEY2-overexpressing hearts reverses mitochondrial and cardiac defects, highlighting the centrality of this metabolic axis.

This establishes HEY2 as a critical transcriptional brake on cardiac mitochondrial metabolism, with direct relevance to the development and progression of heart failure. By mapping the HEY2/HDAC1-Ppargc1/Cpt module, the research opens new avenues for targeting metabolic regulation in cardiac disease.

Comparison with Existing Internal Articles

Several internal resources focus on mRNA modification for protein expression and approaches to mRNA translation enhancement using modified nucleosides, especially N1-Methylpseudouridine and related compounds. For example, "N1-Methylpseudouridine: Atomic Insights into mRNA Translation" explores how this modified nucleoside can optimize translation efficiency and reduce immunogenicity in vitro and in vivo.

The current HEY2 study, while focusing on endogenous gene regulation rather than exogenous mRNA modification, shares conceptual ground with these articles on the theme of translation regulation via eIF2α phosphorylation and the importance of precise transcriptional and translational control in cell fate and function. Where internal articles such as "N1-Methylpseudouridine: Redefining mRNA Modification for Translation" (link) emphasize engineered strategies for maximizing therapeutic protein output, the HEY2 paper exemplifies how endogenous repressors can limit the expression of mitochondrial proteins, influencing cellular ATP production and stress responses.

Both bodies of work highlight the utility of modified nucleosides and regulatory proteins as tools and targets for optimizing gene expression and translation in disease models, though their domains and molecular levers differ.

Limitations and Transferability

While the findings establish a conserved role for HEY2 in cardiac energy metabolism, several limitations should be considered:

• Most experiments focus on cardiomyocytes in zebrafish and mice; the translation of these findings to human heart failure therapy requires further validation [paper].
• The study does not address whether modulating HEY2 levels in non-cardiac tissues would have analogous or adverse effects, limiting cross-domain extrapolation.
• Temporal dynamics are complex: while short-term increases in mitochondrial biogenesis via Ppargc1a can be beneficial, chronic overexpression may be detrimental. Thus, therapeutic approaches must be carefully titrated.

Nevertheless, the delineation of the HEY2/HDAC1-Ppargc1/Cpt axis provides a valuable blueprint for future studies aiming to manipulate cardiac bioenergetics in disease settings.

Protocol Parameters

• assay: Mitochondrial oxygen consumption rate | value_with_unit: Measured in pmol/min/mg protein | applicability: Cardiomyocyte mitochondrial function | rationale: Direct indicator of mitochondrial oxidative phosphorylation rate | source_type: paper | source_link: https://doi.org/10.1038/s41467-024-55557-4
• assay: HEY2 overexpression dose | value_with_unit: Variable, model-dependent | applicability: Zebrafish, mouse, and human cell lines | rationale: Adjusted to mimic patient-relevant upregulation | source_type: paper | source_link: https://doi.org/10.1038/s41467-024-55557-4
• workflow_recommendation: Use of modified nucleoside (e.g., N1-Methylpseudouridine) in mRNA transfection assays | value_with_unit: 1–5 mM | applicability: Mammalian cell transfection | rationale: Enhances translation efficiency and reduces innate immune activation | source_type: workflow_recommendation | source_link: https://www.apexbt.com/n1-methylpseudouridine.html

Why this cross-domain matters, maturity, and limitations

Although the HEY2 study is centered on endogenous transcriptional regulation in cardiac cells, the underlying principle of modulating gene and protein expression has resonance with engineering exogenous mRNA for research or therapeutic purposes. However, direct application of findings on HEY2-mediated repression to mRNA modification strategies—such as those leveraging N1-Methylpseudouridine—remains speculative without further studies explicitly bridging these domains. Researchers should be cautious in extrapolating between endogenous genetic circuits and exogenous nucleoside-modified mRNA systems unless supported by direct comparative datasets.

Outlook

The discovery of the HEY2/HDAC1-Ppargc1/Cpt module as a transcriptional mechanism repressing mitochondrial metabolism provides a new molecular target for interventions in heart failure. By mapping how HEY2 constrains cardiac energy production, this work enhances our understanding of heart disease progression and suggests avenues for metabolic reprogramming to preserve cardiac function. Future research may focus on pharmacological modulation of HEY2 or its downstream effectors, with careful attention to tissue specificity and temporal control, as informed by the present findings.

Research Support Resources

For researchers interested in experimentally dissecting gene expression and translation regulation in mammalian systems, N1-Methylpseudouridine (SKU B8340, APExBIO) is a validated modified nucleoside that enables high-efficiency mRNA translation and reduced immunogenicity in a range of cell lines and in vivo settings [product_spec]. Its properties make it suitable for mRNA-based experimental workflows seeking to maximize protein output and minimize cellular stress, complementing research into translational and metabolic regulation.