Antonicka Hana, Weraarpachai Woranontee, Szigety Katherine M, Kopajtich Robert, Gibson James B, Van Hove Johan L K, Friederich Marisa W, Lopriore Piervito, Neuhofer Christiane, Van Hove Roxanne A, Cole Michel A, Reisdorph Richard, Peterson James T, Dempsey Katherine J, Ganetzky Rebecca D, Mancuso Michelangelo, Prokisch Holger, Shoubridge Eric A
Department of Human Genetics, McGill University, Montreal, QC H3A 2B4, Canada; The Neuro, Montreal Neurological Institute, Montreal, QC H3A 2B4, Canada.
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
Am J Hum Genet. 2025 Jul 3;112(7):1699-1710. doi: 10.1016/j.ajhg.2025.05.007. Epub 2025 Jun 10.
Using exome sequencing, we identified compound heterozygous variants of unknown significance in FASTKD5, a gene that codes for a mitochondrial protein essential for processing mRNAs at non-canonical cleavage sites in the primary mitochondrial transcript, in three subjects with Leigh syndrome, a progressive neurodegenerative disease characterized by lesions in the brainstem and basal ganglia. Among the three subjects, we identified three missense variants and two frameshift variants leading to a premature stop codon. Analysis of fibroblasts from two subjects showed reduced steady-state levels of FASTKD5 protein by immunoblot, reduced translation of the cytochrome c oxidase subunit 1, impaired assembly of complex IV, and a consequent decrease in cytochrome c oxidase enzymatic activity. The extent of these deficiencies appeared to correlate with the severity of the clinical phenotype. Expression of a wild-type FASTKD5 cDNA, but not cDNAs expressing the missense mutations, rescued all the molecular defects in the subjects' fibroblasts, demonstrating that the alleles are pathogenic. Two of the three identified missense mutations resulted in near complete loss of function, while one was hypomorphic, resulting from impaired protein stability. These cases of mitochondrial disease associated with bi-allelic variants in FASTKD5 add to a growing list of primary genetic mutations causing Leigh syndrome associated with complex IV deficiency.
利用外显子组测序，我们在三名患有 Leigh 综合征的受试者中，鉴定出 FASTKD5 基因中意义不明的复合杂合变异。Leigh 综合征是一种进行性神经退行性疾病，其特征为脑干和基底神经节出现病变。FASTKD5 基因编码一种线粒体蛋白，该蛋白对于在线粒体初级转录本的非经典切割位点加工 mRNA 至关重要。在这三名受试者中，我们鉴定出三个错义变异和两个导致提前终止密码子的移码变异。对两名受试者的成纤维细胞进行分析显示，免疫印迹法检测到 FASTKD5 蛋白的稳态水平降低，细胞色素 c 氧化酶亚基 1 的翻译减少，复合物 IV 的组装受损，进而导致细胞色素 c 氧化酶的酶活性降低。这些缺陷的程度似乎与临床表型的严重程度相关。野生型 FASTKD5 cDNA 的表达可挽救受试者成纤维细胞中的所有分子缺陷，而表达错义突变的 cDNA 则不能，这表明这些等位基因具有致病性。所鉴定出的三个错义突变中有两个导致功能几乎完全丧失，而另一个则是由于蛋白质稳定性受损导致功能减弱。这些与 FASTKD5 双等位基因变异相关的线粒体疾病病例，增加了导致与复合物 IV 缺陷相关的 Leigh 综合征的原发性基因突变的数量。
