Mitochondrial dynamics (fission and fusion)

Mitochondrial dynamics is the constant cycle of fission (splitting) and fusion (merging) that reshapes your mitochondrial network as metabolic needs and stress change. Fission is driven by an enzyme called DRP1, pulled to the outer membrane by adaptors (MFF and FIS1). Outer-membrane fusion needs the mitofusins MFN1 and MFN2; inner-membrane fusion needs OPA1. The two processes serve different goals. Fusion lets partly-damaged mitochondria share parts and keep energy production efficient. Fission separates dud segments so they can be cleared by mitophagy (via the PINK1-Parkin pathway). Aging tilts the balance toward fragmentation. Aged rodent neurons, muscle, and eggs show lower DRP1 activity, lower OPA1, and altered MFN2, which hurts energy generation and quality control (Sharma et al. 2019). In human age-related diseases (Parkinson's, type 2 diabetes, sarcopenia), this fission-fusion imbalance goes with impaired mitophagy and a pile-up of broken mitochondria. Whether the imbalance is a primary driver or a downstream consequence of aging in humans is still being studied (Liu et al. 2020).

Last reviewed: June 22, 2026

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