Patient specific regulation of metabolism and cell death pathways in m.3243A>G mutated iPS-cells

The m.3243A>G mitochondrial DNA mutation is one of the most common pathogenic variants associated with mitochondrial disease and its clinical manifestations vary widely among patients. To investigate the mechanisms underlying this variability, we utilized induced pluripotent stem cells (iPSCs) derived from two unrelated patients (P1 and P2) carrying the m.3243A>G mutation. Despite similar heteroplasmy levels, we observed clear patient-specific differences in how the mutations affected iPSC growth and cell death pathways. In patient 2 iPSCs, m.3243A>G reduced cell proliferation and shifted metabolism towards glycolysis, while in patient 1 cells, both oxidative phosphorylation (OXPHOS) and proliferation were slightly enhanced. Susceptibility to apoptosis also differed markedly between the patients. The m.3243A>G mutations reduced apoptosis in P2 iPSCs, in a BCL2 dependent manner, while ferroptosis-related markers such as lipid peroxidation and expression of iron uptake genes were upregulated, suggesting activation of an alternative cell death pathway. Further, ferroptosis inhibition rescued the proliferation defect in P2 iPSCs. In P1, the mutations did not induce cell death by either pathway. Together, these findings demonstrate that the m.3243A>G mutations lead to distinct, patient-specific cellular phenotypes in iPSCs, shaped by differential metabolic reprogramming and cell death regulation. This highlights the importance of personalized disease modeling in mitochondrial disorders and suggests that effective therapeutic strategies may need to be tailored to individual cellular responses.