Very low levels of the mtDNA A3243G mutation associated with mitochondrial dysfunction in vivo.
We studied mitochondrial function in vivo in 2 brothers harboring the mitochondrial DNA A3243G mutation by using magnetic resonance spectroscopy. One brother presented with recurrent strokes and had a mitochondrial respiratory chain complex I defect, with 85% A3243G mutation in his quadriceps. The maximum rate of mitochondrial ATP production in his calf, measured in vivo, was reduced to 21% of the normal mean value. The second brother had mild exercise intolerance, normal muscle histochemistry, and normal respiratory chain activity in vitro. Despite a level of the A3243G mutation of only 5.95% (SD, 4.45; range, 0.7-16.1%) within single muscle fibers from the gastrocnemius muscle, the maximum rate of mitochondrial ATP production in his calf, measured in vivo, was reduced to 35% of the normal mean value. These findings suggest that there may not be a clear genetic threshold level for the expression of the A3243G mutation in skeletal muscle in vivo.
Chinnery
P F
PF
Department of Neurology, University of Newcastle upon Tyne, UK.
Taylor
D J
DJ
Brown
D T
DT
Manners
D
D
Styles
P
P
Lodi
R
R
D000328:Adult; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008931:Mitochondria, Muscle / Q000235:genetics* / Q000378:metabolism*; D017240:Mitochondrial Myopathies / Q000378:metabolism* / Q000503:physiopathology; D009132:Muscles / Q000378:metabolism*; D020521:Stroke / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology
D004272:DNA, Mitochondrial