GFM1 and inborn mitochondrial metabolism disorder: Mutant GFM1 cells present all the necessary features to be considered a good mitochondrial disease model: (1) GFM1 mutation triggers an easily quantifiable decrease in the amount of mitochondrial proteins as well as compromises mitochondrial function, (2) mutant cells grow well in glucose-rich media, (3) a 3-day screening in galactose medium is sufficient to know whether a particular treatment is efficacious or not, (4) high reproducibility of assays irrespective of time differences.