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Original Investigation
July 2018

Selective Genetic Overlap Between Amyotrophic Lateral Sclerosis and Diseases of the Frontotemporal Dementia Spectrum

Author Affiliations
  • 1Department of Psychiatry, Washington University in St Louis, St Louis, Missouri
  • 2Department of Cognitive Sciences, University of California, San Diego, La Jolla
  • 3Memory and Aging Center, Department of Neurology, University of California, San Francisco
  • 4Department of Neuroscience, Mayo Clinic College of Medicine, Jacksonville, Florida
  • 5Department of Translational Neurodegeneration, German Center for Neurodegenerative Diseases, Munich, Germany
  • 6Department of Neurology, Technical University of Munich, Munich Cluster for Systems Neurology SyNergy, Munich, Germany
  • 7Institut for Humangenetik, Justus-Liebig-Universität, Giessen, Germany
  • 8Department of Molecular Neuroscience, Institute of Neurology, University College London, London, United Kingdom
  • 9Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia
  • 10Center for Applied Genomics, Abramson Research Center, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
  • 11Division of Human Genetics, Abramson Research Center, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
  • 12Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia
  • 13Laboratory of Neurogenetics, Department of Internal Medicine, Texas Tech University Health Sciences Center, Lubbock
  • 14Neuroradiology Section, Department of Radiology and Biomedical Imaging, University of California, San Francisco
  • 15Department for Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
  • 16Institute for Clinical Epidemiology and Applied Biometry, University of Tübingen, Tübingen, Germany
  • 17Norwegian Centre for Mental Disorders Research, Institute of Clinical Medicine, University of Oslo, Oslo, Norway
  • 18Division of Mental Health and Addiction, Oslo University Hospital, Oslo, Norway
  • 19Department of Neurosciences, University of California, San Diego, La Jolla
  • 20Department of Neurosciences and Radiology, University of California, San Diego, La Jolla
JAMA Neurol. 2018;75(7):860-875. doi:10.1001/jamaneurol.2018.0372
Key Points

Question  Are there genome-wide genetic risk factors for amyotrophic lateral sclerosis that are shared with other neurodegenerative diseases?

Findings  This study of combined genome-wide association data identified selective genetic overlap between amyotrophic lateral sclerosis and neurodegenerative diseases within the frontotemporal dementia spectrum.

Meaning  These findings identify common genetic pathways between amyotrophic lateral sclerosis and frontotemporal dementia and suggest that MAPT and BNIP1 influence the pathogenesis of amyotrophic lateral sclerosis.

Abstract

Importance  Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by loss of upper and lower motor neurons. Although novel ALS genetic variants have been identified, the shared genetic risk between ALS and other neurodegenerative disorders remains poorly understood.

Objectives  To examine whether there are common genetic variants that determine the risk for ALS and other neurodegenerative diseases and to identify their functional pathways.

Design, Setting, and Participants  In this study conducted from December 1, 2016, to August 1, 2017, the genetic overlap between ALS, sporadic frontotemporal dementia (FTD), FTD with TDP-43 inclusions, Parkinson disease (PD), Alzheimer disease (AD), corticobasal degeneration (CBD), and progressive supranuclear palsy (PSP) were systematically investigated in 124 876 cases and controls. No participants were excluded from this study. Diagnoses were established using consensus criteria.

Main Outcomes and Measures  The primary outcomes were a list of novel loci and their functional pathways in ALS, FTD, PSP, and ALS mouse models.

Results  Among 124 876 cases and controls, genome-wide conjunction analyses of ALS, FTD, PD, AD, CBD, and PSP revealed significant genetic overlap between ALS and FTD at known ALS loci: rs13302855 and rs3849942 (nearest gene, C9orf72; P = .03 for rs13302855 and P = .005 for rs3849942) and rs4239633 (nearest gene, UNC13A; P = .03). Significant genetic overlap was also found between ALS and PSP at rs7224296, which tags the MAPT H1 haplotype (nearest gene, NSF; P = .045). Shared risk genes were enriched for pathways involving neuronal function and development. At a conditional FDR P < .05, 22 novel ALS polymorphisms were found, including rs538622 (nearest gene, ERGIC1; P = .03 for ALS and FTD), which modifies BNIP1 expression in human brains (35 of 137 females; mean age, 59 years; P = .001). BNIP1 expression was significantly reduced in spinal cord motor neurons from patients with ALS (4 controls: mean age, 60.5 years, mean [SE] value, 3984 [760.8] arbitrary units [AU]; 7 patients with ALS: mean age, 56 years, mean [SE] value, 1999 [274.1] AU; P = .02), in an ALS mouse model (mean [SE] value, 13.75 [0.09] AU for 2 SOD1 WT mice and 11.45 [0.03] AU for 2 SOD1 G93A mice; P = .002) and in brains of patients with PSP (80 controls: 39 females; mean age, 82 years, mean [SE] value, 6.8 [0.2] AU; 84 patients with PSP: 33 females, mean age 74 years, mean [SE] value, 6.8 [0.1] AU; β = –0.19; P = .009) or FTD (11 controls: 4 females; mean age, 67 years; mean [SE] value, 6.74 [0.05] AU; 17 patients with FTD: 10 females; mean age, 69 years; mean [SE] value, 6.53 [0.04] AU; P = .005).

Conclusions and Relevance  This study found novel genetic overlap between ALS and diseases of the FTD spectrum, that the MAPT H1 haplotype confers risk for ALS, and identified the mitophagy-associated, proapoptotic protein BNIP1 as an ALS risk gene. Together, these findings suggest that sporadic ALS may represent a selectively pleiotropic, polygenic disorder.

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