Maria Gisatulin1, Valerija Dobricic1, Christine Zühlke1, Yorck Hellenbroich1, Vera Tadic1, Alexander Münchau1, Klaus Isenhardt1, Katrin Bürk1, Melanie Bahlo1, Paul J Lockhart1, Katja Lohmann1, Christoph Helmchen1, Norbert Brüggemann2. 1. 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. 2. 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. norbert.brueggemann@neuro.uni-luebeck.de.
Abstract
OBJECTIVE: To determine the clinical significance of an intronic biallelic pentanucleotide repeat expansion in the gene encoding replication factor C subunit 1 (RFC1) 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. METHODS: 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 RFC1 and the neighboring gene WDR19 were determined by quantitative PCR. RESULTS: 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 RFC1 and WDR19 were unchanged and RFC1 intron retention was not found. CONCLUSIONS: 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.
OBJECTIVE: To determine the clinical significance of an intronic biallelic pentanucleotide repeat expansion in the gene encoding replication factor C subunit 1 (RFC1) 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. METHODS: 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 RFC1 and the neighboring gene WDR19 were determined by quantitative PCR. RESULTS: 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 RFC1 and WDR19 were unchanged and RFC1 intron retention was not found. CONCLUSIONS: 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.
Authors: Marie Beaudin; Mario Manto; Jeremy D Schmahmann; Massimo Pandolfo; Nicolas Dupre Journal: Nat Rev Neurol Date: 2022-03-24 Impact factor: 42.937