clinically heterogeneous, neurogenetic disorder. Using multiple linear regression and linear
mixed modelling, we evaluated which commonly assayed tissue (blood N= 231, urine N=
235, skeletal muscle N= 77) represents the m. 3243A> G mutation load and mitochondrial
DNA (mt DNA) copy number most strongly associated with disease burden and progression.
m. 3243A> G levels are correlated in blood, muscle and urine (R 2= 0.61–0.73). Blood …