Department of Genetics and Metabolic Diseases, Children's Hospital, National Clinical Research Center for Child Health, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China; Division of Medical Genetics and Genomics, Children's Hospital, National Clinical Research Center for Child Health, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China; Institute of Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China.
J Biol Chem. 2020 Sep 18;295(38):13224-13238. doi: 10.1074/jbc.RA120.014603. Epub 2020 Jul 28.
Leber's hereditary optic neuropathy (LHON) is a maternal inheritance of eye disease because of the mitochondrial DNA (mtDNA) mutations. We previously discovered a 3866T>C mutation within the gene for the ND1 subunit of complex I as possibly amplifying disease progression for patients bearing the disease-causing 11778G>A mutation within the gene for the ND4 subunit of complex I. However, whether and how the ND1 mutation exacerbates the ND4 mutation were unknown. In this report, we showed that four Chinese families bearing both m.3866T>C and m.11778G>A mutations exhibited higher penetrances of LHON than 6 Chinese pedigrees carrying only the m.3866T>C mutation or families harboring only the m.11778G>A mutation. The protein structure analysis revealed that the m.3866T>C (I187T) and m.11778G>A (R340H) mutations destabilized the specific interactions with other residues of ND1 and ND4, thereby altering the structure and function of complex I. Cellular data obtained using cybrids, constructed by transferring mitochondria from the Chinese families into mtDNA-less (ρ°) cells, demonstrated that the mutations perturbed the stability, assembly, and activity of complex I, leading to changes in mitochondrial ATP levels and membrane potential and increasing the production of reactive oxygen species. These mitochondrial dysfunctions promoted the apoptotic sensitivity of cells and decreased mitophagy. Cybrids bearing only the m.3866T>C mutation displayed mild mitochondrial dysfunctions, whereas those harboring both m.3866T>C and m.11778G>A mutations exhibited greater mitochondrial dysfunctions. These suggested that the m.3866T>C mutation acted in synergy with the m.11778G>A mutation, aggravating mitochondrial dysfunctions and contributing to higher penetrance of LHON in these families carrying both mtDNA mutations.
Leber 遗传性视神经病变（LHON）是一种母系遗传眼病，因为线粒体 DNA（mtDNA）突变。我们之前发现，在复合体 I 的 ND1 亚单位基因中存在 3866T>C 突变，可能会放大携带复合体 I 的 ND4 亚单位基因中致病 11778G>A 突变的患者的疾病进展。然而，ND1 突变是否以及如何加剧 ND4 突变尚不清楚。在本报告中，我们显示，携带 m.3866T>C 和 m.11778G>A 突变的 4 个中国家族的 LHON 外显率高于仅携带 m.3866T>C 突变的 6 个中国家系或仅携带 m.11778G>A 突变的家系。蛋白质结构分析表明，m.3866T>C（I187T）和 m.11778G>A（R340H）突变破坏了与 ND1 和 ND4 其他残基的特定相互作用，从而改变了复合体 I 的结构和功能。使用从中国家族转移线粒体到 mtDNA 缺失（ρ°）细胞构建的杂种细胞获得的细胞数据表明，突变扰乱了复合体 I 的稳定性、组装和活性，导致线粒体 ATP 水平和膜电位发生变化，并增加了活性氧的产生。这些线粒体功能障碍促进了细胞的凋亡敏感性，并减少了线粒体自噬。仅携带 m.3866T>C 突变的杂种细胞表现出轻微的线粒体功能障碍，而携带 m.3866T>C 和 m.11778G>A 突变的杂种细胞表现出更大的线粒体功能障碍。这表明 m.3866T>C 突变与 m.11778G>A 突变协同作用，加剧了线粒体功能障碍，并导致这些携带两种 mtDNA 突变的家族的 LHON 外显率更高。
