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New publication by MITO team in Neurology: Genetics

Publiée le : 16 juillet 2020

Karine Auré, Guillemette Fayet, Ivan Chicherin, Benoit Rucheton, Sandrine Filaut, Anne-Marie Heckel, Julie Eichler, Florence Caillon, Yann Péréon, Nina Entelis, Ivan Tarassov, Anne Lombès (2020) A homoplasmic mitochondrial tRNAPro mutation causing exercise-induced muscle swelling and fatigue. Neurology: Genetics (in press) Neurol Genet 2020;6:e480. doi:10.1212/NXG.0000000000000480

Abstract

Objective

To demonstrate the causal role in disease of the MT-TP m.15992A>T mutation observed in

patients from 5 independent families.

Methods

Lactate measurement, muscle histology, and mitochondrial activities in patients; PCR-based

analyses of the size, amount, and sequence of muscle mitochondrial DNA (mtDNA) and

proportion of the mutation; respiration, mitochondrial activities, proteins, translation, transfer

RNA (tRNA) levels, and base modification state in skin fibroblasts and cybrids; and reactive

oxygen species production, proliferation in the absence of glucose, and plasma membrane

potential in cybrids.

Results

All patients presented with severe exercise intolerance and hyperlactatemia. They were associated

with prominent exercise-induced muscle swelling, conspicuous in masseter muscles (2

families), and/or with congenital cataract (2 families). MRI confirmed exercise-induced muscle

edema. Muscle disclosed severe combined respiratory defect. Muscle mtDNA had normal size

and amount. Its sequence was almost identical in all patients, defining the haplotype as J1c10,

and sharing 31 variants, only 1 of which, MT-TP m.15992A>T, was likely pathogenic. The

mutation was homoplasmic in all tissues and family members. Fibroblasts and cybrids with

homoplasmic mutation had defective respiration, low complex III activity, and decreased

tRNAPro amount. Their respiratory complexes amount and tRNAPro aminoacylation appeared

normal. Low proliferation in the absence of glucose demonstrated the relevance of the defects

on cybrid biology while abnormal loss of cell volume when faced to plasma membrane depolarization

provided a link to the muscle edema observed in patients.

Conclusions

The homoplasmic MT-TP m.15992A>T mutation in the J1c10 haplotype causes exerciseinduced

muscle swelling and fatigue.

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