Mutations in TENM4, a regulator of axon guidance and central myelination, cause essential tremor. H. Hor1,2,3,4, L. Francescatto5, L. Bartesaghi6, S. Ortega-Cubero7, M. Kousi8, O. Lorenzo- Betancor7, F. J. Jiménez-Jiménez8, A. Gironell9,10, J. Clarimón10,11, O. Drechsel1,2, J. A. G. Agúndez12, D. Kenzelmann Broz13, R. Chiquet-Ehrismann13, A. Lleó10, F. Coria14, E. García-Martin15, H. Alonso-Navarro8, M. J. Martí16, J. Kulisevsky9,11, C. N. Hor1,2,3,4, S. Ossowski1,2, R. Chrast6, N. Katsanis5, P. Pastor7, X. Estivill1,2,3,4,17 1) Bioinformatics and Genomics Program, Centre for Genomic Regulation (CRG), Barcelona, Catalonia, Spain; 2) Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain; 3) Hospital del Mar Medical Research Institute (IMIM), Barcelona, Catalonia, Spain; 4) CIBER de Epidemiología y Salud Pública (CIBERESP), Barcelona, Catalonia, Spain; 5) Center for Human Disease Modeling, Duke University, Duke University Medical Center, Durham, USA; 6) Department of Medical Genetics, University of Lausanne, Lausanne, Switzerland; 7) Neurogenetics Laboratory, Division of Neurosciences, Center for Applied Medical Research (CIMA), and Department of Neurology, Clínica Universidad de Navarra, University of Navarra School of Medicine and Centro de Investigación Biomédica; 8) Section of Neurology, Hospital Universitario del Sureste, Arganda del Rey, Madrid, Spain; 9) Movement Disorders Unit, Neurology Department, Hospital de Sant Pau, Barcelona, Catalonia, Spain; 10) Sant Pau Biomedical Research Institute, Barcelona, Catalonia, Spain; 11) Universitat Autònoma de Barcelona and CIBERNED, Barcelona, Catalonia, Spain; 12) Department of Pharmacology, University of Extremadura, Cáceres, Spain; 13Friedrich Miescher Institute of Biomedical Research, Novartis Research Foundation and University of Basel, Faculty of Sciences and Department of Biomedicine, Basel, Switzerland; 13) Friedrich Miescher Institute of Biomedical Research, Novartis Research Foundation and University of Basel, Faculty of Sciences and Department of Biomedicine, Basel, Switzerland; 14) Clinic for Nervous Disorders, Service of Neurology, Son Espases University Hospital, Palma de Mallorca, Spain; 15) Department of Biochemistry and Molecular Biology, University of Extremadura, Cáceres, Spain; 16) Movement Disorders Unit, Neurology Service, Hospital Clinic, CIBERNED and Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain; 17) Dexeus Womens Health, University Hospital Quiron-Dexeus, Barcelona, Catalonia, Spain.
Introduction: Essential tremor (ET) is the most common movement disorder with an estimated prevalence of 5% in individuals older than 65 years. To date, genetic studies have failed to identify a common genetic cause for this condition. Methods: We performed exome sequencing in an ET family and identified a candidate causal genetic variant in TENM4, which segregated in an autosomal dominant fashion. We then used targeted resequencing in 299 unrelated familial ET cases to identify additional families with segregating mutations in TENM4. We performed in vitro assays in HEK cells and oligodendrocyte precursor cells to elucidate the properties of TENM4, and used a zebrafish model to interrogate the effect of the identified TENM4 mutations. Results: We identified a missense mutation (C4100A) in TENM4 that segregated with ET in a nuclear family. Subsequent targeted resequencing of TENM4 led to the discovery of two novel missense mutations, each of which segregated with ET in two additional families. Consistent with a dominant mode of inheritance, in vitro analysis in either HEK cells or oligodendrocyte precursor cells showed that mutant proteins are both unstable and mislocalize. Finally, expression of human mRNA harboring any of three patient mutations in zebrafish embryos induced defects in axon guidance, confirming a dominant-negative mode of action for these mutations. Conclusion: Our genetic and functional data, which is corroborated by the existence of a Tenm4 knock-out mouse displaying an essential tremor phenotype, implicates TENM4 in ET as a major contributor to the etiopathology of the disorder. Together with previous studies of TENM4 in model organisms, our studies intimate that processes regulating myelination in the central nervous system and axon guidance might be significant contributors to the genetic burden of this disorder.