Identification of Disease-Causing Mutations by Functional Complementation of Patient-Derived Fibroblast Cell Lines

Diagnosis of mitochondrial disorders is still hampered by their phenotypic and genotypic heterogeneity. In many cases, exome sequencing, the state-of-the-art method for genetically diagnosing mitochondrial disease patients, does not allow direct identification of the disease-associated gene but rather results in a list of variants in candidate genes. Here, we present a method to validate the disease-causing variant based on functional complementation assays. First, cell lines expressing a wild-type cDNA of the candidate genes are generated by lentiviral infection of patient-derived fibroblasts. Next, oxidative phosphorylation is measured by the Seahorse XF analyzer to assess rescue efficiency.