Varied Responses to a High m.3243A>G Mutation Load and Respiratory Chain Dysfunction in Patient-Derived...

Area of Science:

• Genetics
• Molecular Biology
• Cardiology

Background:

• The m.3243A>G mutation in mitochondrial DNA is a frequent cause of human disease.
• Clinical presentations of this mutation are highly variable, with unknown reasons for differences in severity.
• Cardiac disease, including cardiomyopathy, affects about one-third of patients and is a major cause of mortality.

Purpose of the Study:

• To investigate the molecular mechanisms underlying the clinical variability of the m.3243A>G mitochondrial DNA mutation.
• To examine the impact of high mutation load on cardiomyocyte function using patient-derived induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).

Main Methods:

• Utilized iPSC-CMs from two m.3243A>G patients, one with severe cardiomyopathy and one without.
• Assessed mitochondrial respiration, cellular metabolism (glucose utilization), ATP levels, and intracellular calcium signaling in iPSC-CMs.

Main Results:

• High m.3243A>G mutation load impaired mitochondrial respiration in iPSC-CMs from both patients.
• Cells from the patient without heart disease exhibited increased glucose metabolism and maintained ATP levels.
• Cells from the patient with cardiomyopathy showed reduced ATP levels and altered intracellular calcium signaling.

Conclusions:

• The study highlights how varying metabolic and signaling pathways contribute to the clinical heterogeneity observed in m.3243A>G mitochondrial disease.
• Patient-specific iPSC-CMs are valuable models for understanding tissue-specific manifestations of mitochondrial disorders.