Novel Mutations Associated with Mitochondrial Disorder: Functional Characterization in Patient Fibroblasts and .

Genetic defects in the nuclear encoded subunits and assembly factors of cytochrome c oxidase (mitochondrial complex IV) are very rare and are associated with a wide variety of phenotypes. Biallelic pathogenic variants in the COX11 protein were previously identified in two unrelated children with infantile-onset mitochondrial encephalopathies. Through comprehensive clinical, genetic and functional analyses, here we report on a new patient harboring novel heterozygous variants in , presenting with Leigh-like features, and provide additional experimental evidence for a direct correlation between COX11 protein expression and sensitivity to oxidative stress.