Oligogenic basis of sporadic ALS: The example of SOD1 p.Ala90Val mutation

Liina Kuuluvainen; Karri Kaivola; Saana Mönkäre; Hannu Laaksovirta; Manu Jokela; Bjarne Udd; Miko Valori; Petra Pasanen; Anders Paetau; Bryan J Traynor; David J Stone; Johanna Schleutker; Minna Pöyhönen; Pentti J Tienari; Liisa Myllykangas

doi:10.1212/NXG.0000000000000335

Oligogenic basis of sporadic ALS: The example of SOD1 p.Ala90Val mutation

Neurol Genet. 2019 Apr 23;5(3):e335. doi: 10.1212/NXG.0000000000000335. eCollection 2019 Jun.

Authors

Affiliation

¹ Department of Clinical Genetics (L.K.), Helsinki University Hospital; Department of Medical Genetics (L.K.), University of Helsinki, Helsinki, Finland; Molecular Neurology (K.K., M.V., P.J.T.), Research Programs Unit, Biomedicum, University of Helsinki, Helsinki, Finland; Department of Medical Genetics (S.M.), University of Helsinki, Helsinki, Finland and Turku; University Hospital (S.M.), Laboratory Division, Genetics and Saske, Department of Medical Genetics, Turku, Finland; Department of Neurology (H.L.), Helsinki University Hospital, and Molecular Neurology, Research Programs Unit, Biomedicum, University of Helsinki, Helsinki, Finland; Neuromuscular Research Center (M.J., B.U.), Tampere University Hospital and University of Tampere, Tampere, Finland; Division of Clinical Neurosciences (M.J.), Turku University Hospital and University of Turku, Turku, Finland; Folkhälsan Research Center (B.U.), Biomedicum, University of Helsinki, Helsinki, Finland; Institute of Biomedicine (P.P., J.S.), University of Turku; Turku University Hospital (P.P., J.S.), Laboratory Division, Genetics and Saske, Department of Medical Genetics, Turku, Finland; Department of Pathology (A.P.), University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Laboratory of Neurogenetics (B.J.T.), National Institute on Aging, National Institutes of Health, Bethesda, MD; Merck & Co. (D.J.S.), Inc., West Point, PA; Department of Clinical Genetics (M.P.), Helsinki University Hospital; Department of Medical Genetics (M.P.), University of Helsinki, Helsinki, Finland; Department of Neurology (P.J.T.), Helsinki University Hospital; and Department of Pathology (L.M.), University of Helsinki and Helsinki University Hospital, Helsinki, Finland.

Abstract

Objective: To characterize the clinical and neuropathologic features of patients with amyotrophic lateral sclerosis (ALS) with the superoxide dismutase 1 (SOD1) p.Ala90Val mutation, as well as the mutation frequency and the role of oligogenic mechanisms in disease penetrance.

Methods: An index patient with autopsy-proven ALS was discovered to have the SOD1 p.Ala90Val mutation, which was screened in 2 Finnish ALS cohorts (n = 453). Additional contributing variants were analyzed from whole-genome or whole-exome sequencing data.

Results: Seven screened patients (1.5%) were found to carry the SOD1 heterozygous mutation. Allele-sharing analysis suggested a common founder haplotype. Common clinical features included limb-onset, long disease course, and sensory symptoms. No TDP43 pathology was observed. All cases were apparently sporadic, and pedigree analysis demonstrated that the mutation has reduced penetrance. Analysis of other contributing genes revealed a unique set of additional variants in each patient. These included previously described rare ANG and SPG11 mutations. One patient was compound heterozygous for SOD1 p.Ala90Val and p.Asp91Ala.

Conclusions: Our data suggest that the penetrance of SOD1 p.Ala90Val is modulated by other genes and indicates highly individual oligogenic basis of apparently sporadic ALS. Additional genetic variants likely contributing to disease penetrance were very heterogeneous, even among Finnish patients carrying the SOD1 founder mutation.

Grants and funding

Z01 AG000949/ImNIH/Intramural NIH HHS/United States