Yap Zheng Yie, Strucinska Klaudia, Matsuzaki Satoshi, Lee Sukyeong, Si Yue, Humphries Kenneth, Tarnopolsky Mark A, Yoon Wan Hee
Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.
J Inherit Metab Dis. 2021 Mar;44(2):388-400. doi: 10.1002/jimd.12248. Epub 2020 Jun 24.
2-Oxoglutarate dehydrogenase (OGDH) is a rate-limiting enzyme in the mitochondrial TCA cycle, encoded by the OGDH gene. α-Ketoglutarate dehydrogenase (OGDH) deficiency was previously reported in association with developmental delay, hypotonia, and movement disorders and metabolic decompensation, with no genetic data provided. Using whole exome sequencing, we identified two individuals carrying a homozygous missense variant c.959A>G (p.N320S) in the OGDH gene. These individuals presented with global developmental delay, elevated lactate, ataxia and seizure. Fibroblast analysis and modeling of the mutation in Drosophila were used to evaluate pathogenicity of the variant. Skin fibroblasts from subject # 2 showed a decrease in both OGDH protein and enzyme activity. Transfection of human OGDH cDNA in HEK293 cells carrying p.N320S also produced significantly lower protein levels compared to those with wild-type cDNA. Loss of Drosophila Ogdh (dOgdh) caused early developmental lethality, rescued by expressing wild-type dOgdh (dOgdh ) or human OGDH (OGDH ) cDNA. In contrast, expression to the mutant OGDH (OGDH ) or dOgdh carrying homologous mutations to human OGDH p.N320S variant (dOgdh ) failed to rescue lethality of dOgdh null mutants. Knockdown of dOgdh in the nervous system resulted in locomotion defects which were rescued by dOgdh expression but not by dOgdh expression. Collectively, the results indicate that c.959A>G variant in OGDH leads to an amino acid change (p.N320S) causing a severe loss of OGDH protein function. Our study establishes in the first time a genetic link between an OGDH gene mutation and OGDH deficiency.
2-氧代戊二酸脱氢酶（OGDH）是线粒体三羧酸循环中的一种限速酶，由OGDH基因编码。先前有报道称α-酮戊二酸脱氢酶（OGDH）缺乏与发育迟缓、肌张力减退、运动障碍和代谢失代偿有关，但未提供遗传数据。通过全外显子组测序，我们鉴定出两名个体在OGDH基因中携带纯合错义变体c.959A>G（p.N320S）。这些个体表现出全面发育迟缓、乳酸升高、共济失调和癫痫发作。使用成纤维细胞分析和果蝇中的突变建模来评估该变体的致病性。受试者2的皮肤成纤维细胞显示OGDH蛋白和酶活性均降低。与野生型cDNA相比，在携带p.N320S的HEK293细胞中转染人OGDH cDNA也产生了明显较低的蛋白水平。果蝇Ogdh（dOgdh）的缺失导致早期发育致死，通过表达野生型dOgdh（dOgdh）或人OGDH（OGDH）cDNA可挽救。相比之下，表达突变型OGDH（OGDH）或携带与人OGDH p.N320S变体同源突变的dOgdh（dOgdh）未能挽救dOgdh无效突变体的致死性。在神经系统中敲低dOgdh会导致运动缺陷，通过dOgdh表达可挽救，但dOgdh表达不能挽救。总体而言，结果表明OGDH中的c.959A>G变体导致氨基酸变化（p.N320S），从而导致OGDH蛋白功能严重丧失。我们的研究首次建立了OGDH基因突变与OGDH缺乏之间的遗传联系。
