NDUFAF4 and neurodegenerative disease: To this end, we used as recipient cells healthy fibroblasts, fibroblasts taken from a patient with a mutation in the gene C6orf66, which encodes the NDUFAF4 protein, an assembly factor of complex I of the respiratory chain, and G229C/Y35X cells, fibroblasts taken from a patient, with the G229C/Y35X mutation which manifests neonatal period with recurrent liver failure and severe neurodegenerative disease from early infancy23.