NDUFS8 and Leigh syndrome: The TAT-C6ORF66 fusion protein, added to cultured patients’ cells, localized within the mitochondria, where it led to the proper assembly and most importantly, restored the function of complex I. Similarly, Lin et al. [61] conjugated TAT with NADH dehydrogenase (ubiquinone) Fe–S protein 8 (NDUFS8), the first complex I subunit linked to Leigh syndrome, and the resulting TAT-NDUFS8 or NDUFS8-TAT fusion proteins were successfully delivered into mitochondria.