A transcriptional enhancer regulates cardiac maturation

Area of Science:

• Cardiology
• Molecular Biology
• Stem Cell Biology

Background:

• Cardiomyocyte maturation is essential for adult heart function and the use of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs).
• The precise regulatory mechanisms, particularly at the cis-regulatory element level, governing cardiomyocyte maturation and their link to heart disease are not fully understood.
• Alpha-actinin 2 (ACTN2) expression increases during cardiomyocyte maturation, suggesting its regulatory elements are important.

Purpose of the Study:

• To investigate the role of a conserved ACTN2 enhancer in cardiomyocyte maturation and cardiac function.
• To explore the impact of ACTN2 enhancer dysfunction on heart disease mechanisms.
• To assess the potential of modulating this enhancer for therapeutic benefit in hPSC-CMs.

Main Methods:

• Utilized human pluripotent stem cell (hPSC) and mouse models to study the ACTN2 enhancer.
• Generated heterozygous ACTN2 enhancer deletion models.
• Performed transcriptomic analyses (in vitro and in vivo).
• Employed enhancer CRISPR activation (enCRISPRa) to target the ACTN2 enhancer.

Main Results:

• Heterozygous deletion of the ACTN2 enhancer resulted in abnormal cardiomyocyte morphology, reduced cardiac function, and impaired mitochondrial respiration.
• Transcriptomic analysis revealed disrupted cardiomyocyte maturation pathways and upregulated mammalian target of rapamycin (mTOR) signaling, leading to senescence.
• ACTN2 enhancer deletion increased heat shock protein 90A expression, a mediator of mTOR activation.
• Enhancer CRISPR activation of the ACTN2 enhancer successfully promoted hPSC-CM maturation.

Conclusions:

• A specific transcriptional enhancer plays a critical role in regulating cardiac maturation and cardiomyocyte physiology.
• Dysregulation of this enhancer contributes to cardiac dysfunction and disease phenotypes by impacting mTOR signaling and promoting senescence.
• Targeting this enhancer offers a potential strategy for modulating cardiomyocyte maturation and treating heart disease.