[Identification and functional analysis of combined oxidative phosphorylation deficiency 28 gene mutation].

Objective: To report a case of combined oxidative phosphorylation deficiency 28 (COXPD28) in China, identified the pathogenic mutation and explored the pathogenic mechanism preliminarily. Methods: The clinical characteristics of a patient with COXPD28 were retrospectively analyzed and the pathogenic mutations were identified by mitochondrial gene sequencing and whole exome sequencing. The wild-type and mutant plasmids of pathogenic genes were constructed, and effect of mutation on protein expression by quantitative real-time PCR (qPCR) and Western blot were evaluated. Statistical methods mainly used one-way ANOVA and LSD test. Results: A 21 year old female patient presented with lactic acid poisoning due to repeated chest distress and wheezing since childhood. The sequencing of the whole exon group gene found that solute carrier family 25 member 26 (SLC25A26) gene had a compound heterozygous mutation (c.34G>C, p.A12P; c.197C>A, p.A66E), which was the first report in China. In vitro function test showed that the expression levels of SLC25A26 mRNA and S-adenosylmethionine carrier (SAMC) protein in cells transfected with SLC25A26 mutant plasmid were significantly lower than those transfected with wild type plasmid. The p.A66E mutant plasmid reduced the expression level of SLC25A26 mRNA and SAMC protein to 6% and 26% of wild type plasmids respectively (both P<0.001), while p.A12P mutant plasmid decreased to 62% and 82% of wild type plasmids respectively (P<0.001, P=0.044). When the double mutant (p.A66E+p.A12P) plasmids were co-transfected, the expression levels of SLC25A26 mRNA and SAMC protein decreased to 47% and 57% of the wild type plasmids, respectively (P<0.001, P=0.001). Conclusion: The pathogenic mutation gene of this patient with COXPD28 is SLC25A26 gene mutation (p.A66E, p.A12P), which causes the decrease of SLC25A26 expression level, mitochondrial oxidative phosphorylation dysfunction, and induces COXPD28.目的： 明确1例联合氧化磷酸化缺乏症28型（COXPD28）患者的致病基因突变，初步探索其致病机制。 方法： 回顾性分析2019年8月就诊于山东省立医院集团东营市人民医院1例COXPD28患者的临床特征。通过线粒体基因测序与全外显子组测序明确其致病基因突变，构建致病基因野生型及突变型质粒，通过实时荧光定量PCR与免疫印迹实验评估突变基因对蛋白表达的影响。统计学方法主要采用单因素方差分析及LSD检验。 结果： 患者女性，21岁，因自幼反复胸闷、憋喘就诊，主要表现为乳酸酸中毒。全外显子组基因测序发现溶质载体家族25成员26（SLC25A26）基因存在复合杂合突变（c.34G>C，p.A12P；c.197C>A，p.A66E），查询HGMD数据库，为国内首次报道。体外功能试验证实：与转染野生型质粒相比，细胞转染SLC25A26基因突变质粒后SLC25A26 mRNA及S-腺苷甲硫氨酸载体（SAMC）蛋白表达水平均显著降低，其中p.A66E突变质粒可使SLC25A26 mRNA及SAMC蛋白表达水平分别降为野生型质粒的6%与26%（P值均<0.001），而p.A12P突变质粒则分别降为野生型质粒的62%与82%（P<0.001，P=0.044）；双突变（p.A66E+p.A12P）质粒共转染时，SLC25A26 mRNA与SAMC蛋白表达水平分别降低为野生型质粒的47%与57%（P<0.001，P=0.001）。 结论： 本例COXPD28患者的致病突变基因为SLC25A26基因突变（p.A66E、p.A12P），该突变导致SLC25A26表达水平降低，造成线粒体氧化磷酸化功能障碍，诱发COXPD28。.