The expanding spectrum of nuclear gene mutations in mitochondrial disorders

Our understanding of the molecular basis of mitochondrial disorders has come primarily from the discovery of an expanding number of mutations of mtDNA. However, a variety of recent observations indicate that many syndromes are due to abnormalities in nuclear genes related to oxidative-phosphorylation (OXPHOS). Nuclear genes encode hundreds of proteins involved in mitochondrial OXPHOS. Nevertheless, the identification of these genes has proceeded at a much slower pace, compared with the discovery and characterization of mtDNA mutations. This scenario is rapidly changing, thanks to the discovery of several OXPHOS-related human genes, and to the identification of mutations responsible for different clinical syndromes.