MRM2 and MELAS syndrome: While the patient fibroblasts did not exhibit the same phenotypes ascertained in MRM2 knock-down experiments (Rorbach et al., 2014), complementation of the MRM2 knock-out yeast model with the patient MRM2 variant could not rescue the respiration defect detected, thus supporting the pathogenicity of MRM2 mutation in MELAS syndrome (Garone et al., 2017).