From the Institute of Neurogenetics (M.G., V.D., V.T., K.L., N.B.), Institute of Human Genetics (C.Z., Y.H.), Institute of Systems Motor Science (A.M.), and Center of Brain, Behavior and Metabolism (N.B.), University of Lübeck; Department of Neurology (V.T., C.H., N.B.), University Medical Center Schleswig-Holstein, Campus Lübeck; Department of Neurology (K.I.), Klinikum Aschaffenburg; Department of Neurology (K.B.), Kliniken Schmieder, Stuttgart, Germany; Population Health and Immunity Division (M.B.), The Walter and Eliza Hall Institute of Medical Research; Department of Medical Biology (M.B.), University of Melbourne; Bruce Lefroy Centre (P.J.L.), Murdoch Children's Research Institute; and Department of Pediatrics (P.J.L.), University of Melbourne, Royal Children's Hospital, Parkville, Victoria, Australia.
Neurology. 2020 Nov 24;95(21):e2912-e2923. doi: 10.1212/WNL.0000000000010744. Epub 2020 Sep 1.
To determine the clinical significance of an intronic biallelic pentanucleotide repeat expansion in the gene encoding replication factor C subunit 1 () in patients with late-onset cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS), in patients with other ataxias, and in healthy controls by comprehensive genetic analyses.
In this case-control study, we included 457 individuals comprising 26 patients with complete or incomplete CANVAS, 70 patients with late-onset cerebellar ataxia, 208 healthy controls, and 153 individuals from 39 multigenerational families without ataxia to determine repeat stability. All 96 patients were screened for the repeat expansion by duplex PCR. To further characterize the repeat type and lengths, we used fragment length analysis, repeat-primed PCR, Sanger sequencing, and Southern blotting. Expression of and the neighboring gene were determined by quantitative PCR.
Massive biallelic pentanucleotide expansions were found in 15/17 patients with complete CANVAS (88%), in 2/9 patients with incomplete CANVAS (22%), in 4/70 patients with unspecified, late-onset cerebellar ataxia (6%), but not in controls. In patients, the expansion comprised 800-1,000 mostly AAGGG repeats. Nonmassively expanded repeat numbers were in the range of 7-137 repeats and relatively stable during transmission. Expression of and were unchanged and intron retention was not found.
A biallelic pentanucleotide repeat expansion is a frequent cause of CANVAS and found in a considerable number of patients with an incomplete clinical presentation or other forms of cerebellar ataxia. The mechanism by which the repeat expansions are causing disease remains unclear and warrants further investigations.
通过全面的遗传分析，确定编码复制因子 C 亚基 1 () 基因中内含子双等位基因五核苷酸重复扩增在迟发性小脑共济失调、神经病和前庭反射消失综合征 (CANVAS) 患者、其他共济失调患者和健康对照者中的临床意义。
在这项病例对照研究中，我们纳入了 457 人，包括 26 例完全或不完全 CANVAS 患者、70 例迟发性小脑共济失调患者、208 例健康对照者和 153 名来自 39 个无共济失调的多代家族的个体，以确定重复的稳定性。所有 96 例患者均通过双 PCR 进行重复扩增筛查。为了进一步描述重复类型和长度，我们使用片段长度分析、重复引物 PCR、Sanger 测序和 Southern 印迹。通过定量 PCR 确定 和邻近基因 的表达。
在 17 例完全 CANVAS 患者中（88%）发现大量双等位基因五核苷酸重复扩增，9 例不完全 CANVAS 患者中（22%）发现 2 例，70 例未特指的迟发性小脑共济失调患者中（6%）发现 4 例，但在对照组中未发现。在患者中，该扩增包含 800-1000 个主要为 AAGGG 的重复。非大量扩增的重复数在 7-137 个重复之间，在传递过程中相对稳定。 和 的表达没有改变，也没有发现 内含子保留。
双等位基因五核苷酸重复扩增是 CANVAS 的常见原因，在具有不完全临床表现或其他形式小脑共济失调的患者中发现了相当数量的患者。重复扩增导致疾病的机制尚不清楚，需要进一步研究。
