Calcium Signaling Consequences of RyR2-S4938F Mutation Expressed in Human iPSC-Derived Cardiomyocytes

Area of Science:

• Cardiovascular Biology
• Molecular Cardiology
• Stem Cell Biology

Background:

• Type-2 ryanodine receptor (RyR2) is crucial for cardiac function, regulating calcium (Ca2+) release from the sarcoplasmic reticulum.
• RyR2 dysfunction is linked to arrhythmias, sudden cardiac death, and heart failure.
• Understanding specific RyR2 mutations is vital for developing targeted therapies.

Purpose of the Study:

• To investigate the functional consequences of the S4938F-RyR2 mutation in human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs).
• To analyze the impact of this mutation on Ca2+ signaling and electrophysiological properties.
• To elucidate the underlying mechanisms of the arrhythmogenic phenotype associated with the S4938F-RyR2 mutation.

Main Methods:

• CRISPR/Cas9 gene editing was used to introduce the S4938F-RyR2 mutation into hiPSC-CMs.
• Total internal reflection fluorescence microscopy (TIRF) was employed to study Ca2+ signaling.
• Patch clamp techniques were utilized to assess electrophysiological properties, including L-type Ca2+ currents (ICa).

Main Results:

• hiPSC-CMs with the S4938F-RyR2 mutation exhibited significantly smaller L-type Ca2+ currents (ICa) and associated Ca2+ transients compared to wild-type cells.
• Mutant cells showed larger caffeine-triggered Ca2+ release, indicating increased sarcoplasmic reticulum (SR) Ca2+ content.
• These findings suggest compromised Ca2+-induced Ca2+ release (CICR) and a higher frequency of spontaneous Ca2+ events, contributing to an arrhythmogenic phenotype.

Conclusions:

• The S4938F-RyR2 mutation impairs cardiac Ca2+ handling by reducing ICa and compromising CICR.
• Increased SR Ca2+ content in mutant cells promotes spontaneous Ca2+ release, leading to arrhythmias.
• This study provides insights into the molecular mechanisms of RyR2-mediated cardiac dysfunction and potential therapeutic targets.