Mitochondrial disorders (MD) are a group of multisystem syndromes with a broad phenotypic spectrum. They are associated with mutations in several genes regulating mitochondrial functions, but the molecular defect remains unknown in a large fraction of MD patients. No effective treatment is available for most MD. The use of Next Generation Sequencing (NGS) approaches has allowed the identification of several new disease-genes and would let to improve genetic diagnosis in MD. Mutations in genes coding mitochondrial aminoacyl tRNA synthetases (mtARSs), the enzymes charging a specific tRNA with its cognate amino acid, have been recently described. Often, but not always, there is a strict genotype-phenotype correlation: thanks to unbiased NGS we will better define this issue. We will generate yeast models to confirm the pathogenicity of novel identified variants. Moreover, on subjects harbouring mtARSs mutations we will evaluate amino acid supplementation as a possible therapeutic approach.