Hathazi, DenisaLochmüller, HannsHorvath, Rita2020-11-132020-11-132020Hathazi D, Griffin H, Jennings MJ, Giunta M, Powell C, Pearce SF et al. Metabolic shift underlies recovery in reversible infantile respiratory chain deficiency. EMBO J. 2020 Dec 1;39(23):e105364. DOI: 10.15252/embj.20201053640261-4189http://hdl.handle.net/10230/45751Reversible infantile respiratory chain deficiency (RIRCD) is a rare mitochondrial myopathy leading to severe metabolic disturbances in infants, which recover spontaneously after 6-months of age. RIRCD is associated with the homoplasmic m.14674T>C mitochondrial DNA mutation; however, only ~ 1/100 carriers develop the disease. We studied 27 affected and 15 unaffected individuals from 19 families and found additional heterozygous mutations in nuclear genes interacting with mt-tRNAGlu including EARS2 and TRMU in the majority of affected individuals, but not in healthy carriers of m.14674T>C, supporting a digenic inheritance. Our transcriptomic and proteomic analysis of patient muscle suggests a stepwise mechanism where first, the integrated stress response associated with increased FGF21 and GDF15 expression enhances the metabolism modulated by serine biosynthesis, one carbon metabolism, TCA lipid oxidation and amino acid availability, while in the second step mTOR activation leads to increased mitochondrial biogenesis. Our data suggest that the spontaneous recovery in infants with digenic mutations may be modulated by the above described changes. Similar mechanisms may explain the variable penetrance and tissue specificity of other mtDNA mutations and highlight the potential role of amino acids in improving mitochondrial disease.application/pdfeng© 2020 The Authors Published under the terms of the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/). This is an open access article under the terms of the Creative Commons Attribution 4.0 License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.info:eu-repo/semantics/articlehttp://dx.doi.org/10.15252/embj.2020105364Digenic inheritanceHomoplasmic tRNA mutationMitochondrial myopathyReversible infantile respiratory chain deficiencyinfo:eu-repo/semantics/openAccess