Mitochondrial diseases are caused by nuclear, or mitochondrial DNA (mtDNA) variants and related co-factors. Here, we report a novel m.10197G > C variant in in a patient, and two other patients with m.10191 T > C. variants are known to cause Leigh syndrome or mitochondrial complex I deficiency. We performed the functional analyses of the novel m.10197G > C variant that significantly lowered MT-ND3 protein levels, causing complex I assembly and activity deficiency, and reduction of ATP synthesis. We adapted a previously described re-engineering technique of delivering mitochondrial genes into mitochondria through codon optimization for nuclear expression and translation by cytoplasmic ribosomes to rescue defects arising from the variants. We constructed mitochondrial targeting sequences along with the codon-optimized and imported them into the mitochondria. To achieve the goal, we imported codon-optimized into mitochondria in three patients with m.10197G > C and m.10191 T > C missense variants in the . Nuclear expression of the gene partially restored protein levels, complex I deficiency, and significant improvement of ATP production indicating a functional rescue of the mutant phenotype. The codon-optimized nuclear expression of mitochondrial protein and import inside the mitochondria can supplement the requirements for ATP in energy-deficient mitochondrial disease patients.

中文翻译：

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鉴定新的 MT-ND3 变体并通过 MT-ND3 基因的同位素表达恢复线粒体功能

线粒体疾病是由核或线粒体 DNA (mtDNA) 变异和相关辅助因子引起的。在这里，我们报告了一名患者体内的一种新的 m.10197G > C 变异，另外两名患有 m.10191 T > C 变异的患者已知会导致 Leigh 综合征或线粒体复合物 I 缺陷。我们对新型 m.10197G > C 变体进行了功能分析，该变体显着降低了 MT-ND3 蛋白水平，导致复合物 I 组装和活性缺陷，以及 ATP 合成减少。我们采用了先前描述的重新工程技术，通过密码子优化将线粒体基因传递到线粒体中，以通过细胞质核糖体进行核表达和翻译，以挽救由变异引起的缺陷。我们构建了线粒体靶向序列以及密码子优化并将其导入线粒体中。为了实现这一目标，我们将经过密码子优化的密码子导入三名患者的线粒体中，这些患者的线粒体中存在 m.10197G > C 和 m.10191 T > C 错义变异。该基因的核表达部分恢复了蛋白质水平、复合物 I 缺陷以及 ATP 产生的显着改善，表明突变表型的功能性拯救。线粒体蛋白的密码子优化核表达和线粒体内的输入可以补充能量缺乏的线粒体疾病患者对 ATP 的需求。