FIG. 5.

Proposed model for mitochondrial segregation under accumulation of inherited or stress-mediated mtDNA mutations. Coexistence of wild-type (black circle) and mutated (red circle) mtDNA in the same cell is defined as mtDNA heteroplasmy, directly regulated and selected by constant events of mitochondrial fission, fusion, and mitophagy (142, 192). Defective mitochondrial dynamics results in accumulation of mtDNA mutations, mitochondrial dysfunction, and the consequent reduction of cell viability (117).