Cytochrome c oxidase (COX) deficiency, one of the most common respiratory-chain defects in humans, has been associated with
mutations in either mitochondrial DNA genes or nucleus-encoded proteins that are not part in but promote the biogenesis of COX.
Mutations of nucleus-encoded structural subunits were sought for but never found in COX-defective patients, leading to the conjecture
that they may be incompatible with extra-uterine survival. We report a disease-associated mutation in one such subunit, COX6B1.
Nuclear-encoded COX genes should be reconsidered and included in the diagnostic mutational screening of human disorders related
to COX deficiency.
