Auré Karine, Fayet Guillemette, Chicherin Ivan, Rucheton Benoit, Filaut Sandrine, Heckel Anne-Marie, Eichler Julie, Caillon Florence, Péréon Yann, Entelis Nina, Tarassov Ivan, Lombès Anne
Inserm U1016 Institut Cochin (K.A., B.R., A.L.), INSERM, Paris; Department of Neurophysiology (K.A.), Foch Hospital, Suresnes; Centre de Référence Maladies Neuromusculaires Hôtel-Dieu AOC (G.F., Y.P.), CHU Nantes; CNRS UMR 7156 GMGM (I.C., A.-M.H., J.E., N.E., I.T.), University of Strasbourg; Service de Biochimie Métabolique CHU Pitié-Salpêtrière (B.R., S.F.), AP-HP, Paris; Service de Radiologie et Imagerie Médicale Hôtel-Dieu (F.C.), CHU Nantes; CNRS UMR 8104 (A.L.); Université Paris-Descartes-Paris5 (A.L.), Paris, France; and Present Address: M.V. Lomonossov State University (I.C.), Moscow, Russia.
Neurol Genet. 2020 Jul 15;6(4):e480. doi: 10.1212/NXG.0000000000000480. eCollection 2020 Aug.
To demonstrate the causal role in disease of the m.15992A>T mutation observed in patients from 5 independent families.
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.
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, 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 tRNA amount. Their respiratory complexes amount and tRNA 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.
The homoplasmic m.15992A>T mutation in the J1c10 haplotype causes exercise-induced muscle swelling and fatigue.
证明在5个独立家系患者中观察到的m.15992A>T突变在疾病中的因果作用。
对患者进行乳酸测量、肌肉组织学检查和线粒体活性检测；基于聚合酶链反应（PCR）分析肌肉线粒体DNA（mtDNA）的大小、数量和序列以及突变比例；检测皮肤成纤维细胞和胞质杂种的呼吸作用、线粒体活性、蛋白质、翻译、转运RNA（tRNA）水平和碱基修饰状态；以及胞质杂种中的活性氧产生、无葡萄糖时的增殖和质膜电位。
所有患者均表现为严重运动不耐受和高乳酸血症。他们伴有明显的运动诱发肌肉肿胀，在咬肌中明显（2个家系），和/或伴有先天性白内障（2个家系）。磁共振成像（MRI）证实了运动诱发的肌肉水肿。肌肉显示严重的联合呼吸缺陷。肌肉mtDNA大小和数量正常。其序列在所有患者中几乎相同，确定单倍型为J1c10，并共有31个变异，其中只有1个，即m.15992A>T，可能具有致病性。该突变在所有组织和家庭成员中均为纯质性。具有纯质突变的成纤维细胞和胞质杂种呼吸作用有缺陷，复合体III活性低，tRNA数量减少。它们的呼吸复合体数量和tRNA氨酰化似乎正常。无葡萄糖时增殖低表明这些缺陷与胞质杂种生物学相关，而面对质膜去极化时细胞体积异常减少则与患者中观察到的肌肉水肿相关。
J1c10单倍型中的纯质m.15992A>T突变导致运动诱发的肌肉肿胀和疲劳。
