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Steel, Dora; Zech, Michael; Zhao, Chen; Barwick, Katy E. S.; Burke, Derek; Demailly, Diane; Kumar, Kishore R.; Zorzi, Giovanna; Nardocci, Nardo; Kaiyrzhanov, Rauan; Wagner, Matias; Iuso, Arcangela; Berutti, Riccardo; Skorvanek, Matej; Necpal, Jan; Davis, Ryan; Wiethoff, Sarah; Mankad, Kshitij; Sudhakar, Sniya; Ferrini, Arianna; Sharma, Suvasini; Kamsteeg, Erik-Jan; Tijssen, Marina A.; Verschuuren, Corien; Egmond, Martje E. van; Flowers, Joanna M.; McEntagart, Meriel; Tucci, Arianna; Coubes, Philippe; Bustos, Bernabe I.; Gonzalez-Latapi, Paulina; Tisch, Stephen; Darveniza, Paul; Gorman, Kathleen M.; Peall, Kathryn J.; Bötzel, Kai; Koch, Jan C.; Kmiec, Tomasz; Plecko, Barbara; Boesch, Sylvia; Haslinger, Bernhard; Jech, Robert; Garavaglia, Barbara; Wood, Nick; Houlden, Henry; Gissen, Paul; Lubbe, Steven J.; Sue, Carolyn M.; Cif, Laura; Mencacci, Niccolo E.; Anderson, Glenn; Kurian, Manju A. and Winkelmann, Juliane (2020): Loss-of-Function Variants in HOPS Complex Genes VPS16 and VPS41 Cause Early Onset Dystonia Associated with Lysosomal Abnormalities. In: Annals of Neurology, Vol. 88, No. 5: pp. 867-877 [PDF, 20MB]

Abstract

Objectives: The majority of people with suspected genetic dystonia remain undiagnosed after maximal investigation, implying that a number of causative genes have not yet been recognized. We aimed to investigate this paucity of diagnoses. Methods We undertook weighted burden analysis of whole-exome sequencing (WES) data from 138 individuals with unresolved generalized dystonia of suspected genetic etiology, followed by additional case-finding from international databases, first for the gene implicated by the burden analysis (VPS16), and then for other functionally related genes. Electron microscopy was performed on patient-derived cells. Results Analysis revealed a significant burden forVPS16(Fisher's exact testpvalue, 6.9 x 10(9)).VPS16encodes a subunit of the homotypic fusion and vacuole protein sorting (HOPS) complex, which plays a key role in autophagosome-lysosome fusion. A total of 18 individuals harboring heterozygous loss-of-functionVPS16variants, and one with a microdeletion, were identified. These individuals experienced early onset progressive dystonia with predominant cervical, bulbar, orofacial, and upper limb involvement. Some patients had a more complex phenotype with additional neuropsychiatric and/or developmental comorbidities. We also identified biallelic loss-of-function variants inVPS41, another HOPS-complex encoding gene, in an individual with infantile-onset generalized dystonia. Electron microscopy of patient-derived lymphocytes and fibroblasts from both patients withVPS16andVPS41showed vacuolar abnormalities suggestive of impaired lysosomal function. Interpretation Our study strongly supports a role for HOPS complex dysfunction in the pathogenesis of dystonia, although variants in different subunits display different phenotypic and inheritance characteristics. ANN NEUROL 2020

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