背景:遗传性痉挛性截瘫(HSP)是以进行性下肢痉挛为特征的神经系统疾病。尽管鉴定了几个HSP相关基因,许多患者缺乏基因诊断。
目的:目的是证实双等位基因COQ4突变在HSP中的致病作用,遗传,和COQ4相关HSP的功能分子特征。
方法:分析了来自三个不同人群的310名不明原因HSP指标患者的全外显子组序列,以鉴定潜在的HSP致病基因。检查了从具有候选因果突变的患者获得的临床数据。使用生物信息学工具进行COQ4变体的功能表征,单细胞RNA测序,细胞系中的生化检测,原代成纤维细胞,诱导多能干细胞来源的锥体神经元,还有斑马鱼.
结果:COQ4中的复合杂合变体,在家系中与HSP分离,在来自六个不相关家庭的7名患者中发现。来自六个家庭中的四个患者出现纯HSP,而其他两个家庭的先证者表现出复杂的HSP伴癫痫或小脑共济失调。在患者来源的成纤维细胞和COQ4敲除互补系中,这些错义变体的稳定表达产生了功能丧失效应,包括线粒体活性氧的积累,线粒体膜电位降低,和降低泛醌的生物合成。而分化的锥体神经元表达高COQ4水平,coq4敲低斑马鱼表现出严重的运动功能障碍,反映运动神经元失调。
结论:我们的研究证实了功能丧失,复合杂合,致病性COQ4变异是常染色体隐性遗传纯和复杂HSP的原因。此外,可归因于变体的COQ4水平降低与泛醌生物合成降低相对应,线粒体功能受损,和更高的表型疾病严重程度。©2023国际帕金森和运动障碍协会。
BACKGROUND: Hereditary spastic paraplegias (HSP) are neurologic disorders characterized by progressive lower-extremity spasticity. Despite the identification of several HSP-related genes, many patients lack a genetic diagnosis.
OBJECTIVE: The aims were to confirm the pathogenic role of biallelic COQ4 mutations in HSP and elucidate the clinical, genetic, and functional molecular features of COQ4-associated HSP.
METHODS: Whole exome sequences of 310 index patients with HSP of unknown cause from three distinct populations were analyzed to identify potential HSP causal genes. Clinical data obtained from patients harboring candidate causal mutations were examined. Functional characterization of COQ4 variants was performed using bioinformatic tools, single-cell RNA sequencing, biochemical assays in cell lines, primary fibroblasts, induced pluripotent stem cell-derived pyramidal neurons, and zebrafish.
RESULTS: Compound heterozygous variants in COQ4, which cosegregated with HSP in pedigrees, were identified in 7 patients from six unrelated families. Patients from four of the six families presented with pure HSP, whereas probands of the other two families exhibited complicated HSP with epilepsy or with cerebellar ataxia. In patient-derived fibroblasts and COQ4 knockout complementation lines, stable expression of these missense variants exerted loss-of-function effects, including mitochondrial reactive oxygen species accumulation, decreased mitochondrial membrane potential, and lower ubiquinone biosynthesis. Whereas differentiated pyramidal neurons expressed high COQ4 levels, coq4 knockdown zebrafish displayed severe motor dysfunction, reflecting motor neuron dysregulation.
CONCLUSIONS: Our study confirms that loss-of-function, compound heterozygous, pathogenic COQ4 variants are causal for autosomal recessive pure and complicated HSP. Moreover, reduced COQ4 levels attributable to variants correspond with decreased ubiquinone biosynthesis, impaired mitochondrial function, and higher phenotypic disease severity. © 2023 International Parkinson and Movement Disorder Society.