Table 1.

Mutated mtDNA replication genes and associated human mitochondrial disorders.

Disorders*	Mutated gene	Frequent clinical symptoms
Alpers’ syndrome	POLG1 (pol γ-α)	Progressive spastic quadriparesis, cerebral degeneration, seizures, blindness, deafness, death before 42 months of age
Ataxia-neuropathy syndrome	POLG1 (pol γ-α)	Peripheral neuropathy, cognitive impairment, involuntary movement, psychiatric symptoms, seizures
Autosomal dominant/recessive PEO	POLG1 (pol γ-α)	Bilateral ptosis, weakening of eye muscle, wasting, exercise intolerance
	POLG2 (pol γ-β)
	C10orf2 (Twinkle)

^*Mutations in the POLG1 gene have been associated with many diseases which are not listed here. For a more detailed list of these diseases, please refer to Stumpf and Copeland (2011) and Cohen and Naviaux (2010).