Abstract：
Hepatoencephalopathy due to combined oxidative phosphorylation deficiency type 1 (COXPD1) is a recessive mitochondrial translation disorder caused by mutations in GFM1, a nuclear gene encoding mitochondrial elongation factor G1 (EFG1). Patients with COXPD1 typically present hepatoencephalopathy early after birth with rapid disease progression, and usually die within the first few weeks or years of life. We have generated two different mouse models: a Gfm1 knock-in (KI) harboring the p.R671C missense mutation, found in at least 10 patients who survived more than 1 year, and a Gfm1 knock-out (KO) model. Homozygous KO mice (Gfm1-/- ) were embryonically lethal, whereas homozygous KI (Gfm1R671C / R671C ) mice were viable and showed normal growth. R671C mutation in Gfm1 caused drastic reductions in the mitochondrial EFG1 protein content in different organs. Six- to eight-week-old Gfm1R671C / R671C mice showed partial reductions of in organello mitochondrial translation and respiratory complex IV enzyme activity in the liver. Compound heterozygous Gfm1R671C /- showed a more pronounced decrease of EFG1 protein in liver and brain mitochondria, as compared with Gfm1R671C / R671C mice. At 8 weeks of age, their mitochondrial translation rates were significantly reduced in both tissues. Additionally, Gfm1R671C /- mice showed combined oxidative phosphorylation deficiency (reduced complex I and IV enzyme activities in liver and brain), and blue native polyacrylamide gel electrophoresis analysis revealed lower amounts of both affected complexes. We conclude that the compound heterozygous Gfm1R671C /- mouse presents a clear dysfunctional molecular phenotype, showing impaired mitochondrial translation and combined respiratory chain dysfunction, making it a suitable animal model for the study of COXPD1.
摘要：
由1型联合氧化磷酸化缺陷症（COXPD1）引起的肝性脑病是由GFM1突变引起的隐性线粒体翻译障碍，GFM1是编码线粒体延伸因子G1（EFG1）的核基因。COXPD1患者通常在出生后早期出现肝性脑病，疾病进展迅速，通常在生命的最初几周或几年内死亡。我们已经产生了两种不同的小鼠模型：Gfm1敲入（KI）带有p.R671C错义突变，在至少10名存活超过1年的患者中发现，和Gfm1敲除(KO)模型。纯合KO小鼠（Gfml-/-）是胚胎致死的，而纯合KI(Gfm1R671C/R671C)小鼠是活的并且显示正常生长。Gfm1中的R671C突变导致不同器官中线粒体EFG1蛋白含量急剧下降。6至8周龄的Gfm1R671C/R671C小鼠显示肝脏中器官线粒体翻译和呼吸复合物IV酶活性的部分降低。复合杂合子Gfm1R671C/-显示肝脏和脑线粒体中EFG1蛋白的下降更明显，与Gfm1R671C/R671C小鼠相比。在8周龄时，两种组织的线粒体翻译率均显著降低.此外,Gfm1R671C/-小鼠表现出联合氧化磷酸化缺陷（肝脏和大脑中复合物I和IV酶活性降低），和蓝色天然聚丙烯酰胺凝胶电泳分析显示，两种受影响的复合物的含量较低。我们得出结论，复合杂合子Gfm1R671C/-小鼠表现出明显的功能失调的分子表型，显示线粒体翻译受损和联合呼吸链功能障碍，使其成为研究COXPD1的合适动物模型。
