AUTHOR=Cooper-Knock Johnathan , Robins Henry , Niedermoser Isabell , Wyles Matthew , Heath Paul R. , Higginbottom Adrian , Walsh Theresa , Kazoka Mbombe , Project MinE ALS Sequencing Consortium , Ince Paul G. , Hautbergue Guillaume M. , McDermott Christopher J. , Kirby Janine , Shaw Pamela J. , Kheifat Ahmad Al , Al-Chalabi Ammar , Basak Nazli , Blair Ian , Dekker Annelot , Hardiman Orla , Hide Winston , Iacoangeli Alfredo , Kenna Kevin , Landers John , McLaughlin Russel , Mill Jonathan , Middelkoop Bas , Moisse Mattieu , Mora Pardina Jesus , Morrison Karen , Newhouse Stephen , Pulit Sara , Shatunov Aleksey , Shaw Chris , Sproviero William , Tazelaar Gijs , van Damme Philip , van den Berg Leonard , van der Spek Rick , Eijk Kristelvan , van Es Michael , van Rheenen Wouter , van Vugt Joke , Veldink Jan , Kooyman Maarten , Glass Jonathan , Robberecht Wim , Gotkine Marc , Drory Vivian , Kiernan Matthew , Mitne Neto Miguel , Ztaz Mayana , Couratier Philippe , Corcia Philippe , Silani Vincenzo , Chio Adriano , de Carvalho Mamede , Pinto Susana , Garcia Redondo Alberto , Andersen Peter , Weber Markus , Ticozzi Nicola TITLE=Targeted Genetic Screen in Amyotrophic Lateral Sclerosis Reveals Novel Genetic Variants with Synergistic Effect on Clinical Phenotype JOURNAL=Frontiers in Molecular Neuroscience VOLUME=10 YEAR=2017 URL=https://www.frontiersin.org/journals/molecular-neuroscience/articles/10.3389/fnmol.2017.00370 DOI=10.3389/fnmol.2017.00370 ISSN=1662-5099 ABSTRACT=

Amyotrophic lateral sclerosis (ALS) is underpinned by an oligogenic rare variant architecture. Identified genetic variants of ALS include RNA-binding proteins containing prion-like domains (PrLDs). We hypothesized that screening genes encoding additional similar proteins will yield novel genetic causes of ALS. The most common genetic variant of ALS patients is a G4C2-repeat expansion within C9ORF72. We have shown that G4C2-repeat RNA sequesters RNA-binding proteins. A logical consequence of this is that loss-of-function mutations in G4C2-binding partners might contribute to ALS pathogenesis independently of and/or synergistically with C9ORF72 expansions. Targeted sequencing of genomic DNA encoding either RNA-binding proteins or known ALS genes (n = 274 genes) was performed in ALS patients to identify rare deleterious genetic variants and explore genotype-phenotype relationships. Genomic DNA was extracted from 103 ALS patients including 42 familial ALS patients and 61 young-onset (average age of onset 41 years) sporadic ALS patients; patients were chosen to maximize the probability of identifying genetic causes of ALS. Thirteen patients carried a G4C2-repeat expansion of C9ORF72. We identified 42 patients with rare deleterious variants; 6 patients carried more than one variant. Twelve mutations were discovered in known ALS genes which served as a validation of our strategy. Rare deleterious variants in RNA-binding proteins were significantly enriched in ALS patients compared to control frequencies (p = 5.31E-18). Nineteen patients featured at least one variant in a RNA-binding protein containing a PrLD. The number of variants per patient correlated with rate of disease progression (t-test, p = 0.033). We identified eighteen patients with a single variant in a G4C2-repeat binding protein. Patients with a G4C2-binding protein variant in combination with a C9ORF72 expansion had a significantly faster disease course (t-test, p = 0.025). Our data are consistent with an oligogenic model of ALS. We provide evidence for a number of entirely novel genetic variants of ALS caused by mutations in RNA-binding proteins. Moreover we show that these mutations act synergistically with each other and with C9ORF72 expansions to modify the clinical phenotype of ALS. A key finding is that this synergy is present only between functionally interacting variants. This work has significant implications for ALS therapy development.