The power of yeast in modeling human mutations leading to mitochondrial disease

The term “Mitochondrial disease” refers to a broad range of disorders, each of which involves a mitochondrial dysfunction, in which the underlying genetic defect is often unknown. Whereas the huge increase of alleged mutations identified in single patients, for example by new generation sequencing techniques, a major challenge is to determine if these are the specific cause of the pathology, i.e. it is necessary to validate them. To prove unequivocally the causality, which must be evaluated biologically through functional analyses, the yeast Saccharomyces cerevisiae is extensively used. We also used S. cerevisiae to identify the molecular mechanism underlying human pathologies determined by mutations in genes characterized by mitochondrial dysfunction taking advantage of the presence of homologous genes. In particular, to deepen the pathogenic effect of the mutations, it is possible investigate whether they: a) prevent the correct protein localization into the mitochondria, taking advantage of strains expressing HA-tagged gene recombinant variants; b) affect the stability of the proteins, determining the steady-state level of the mutated proteins by Western blot analysis on mitochondrial protein fraction; c) affect the transcript levels by Real Time transcriptional analysis; d) affect the assembly/stability of complexes, of which the protein is possibly part. These series of opportunities that a simple model organism can provide result in broad interest to researchers in the field. In particular, researchers dealing with human mitochondrial diseases could find, in yeast, if the gene is evolutionarily conserved, an answer to their uncertainties when the analysis of patients’ human tissues or fibroblasts is hardly or not realizable.