Co-aggregation of RNA binding proteins in ALS spinal motor neurons: evidence of a common pathogenic mechanism

• Published in: Acta neuropathologica 2012-11, Vol.124 (5), p.733-747
• Main Authors: Keller, Brian A., Volkening, Kathryn, Droppelmann, Cristian A., Ang, Lee Cyn, Rademakers, Rosa, Strong, Michael J.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Amyotrophic lateral sclerosis; Amyotrophic Lateral Sclerosis - classification; Amyotrophic Lateral Sclerosis - genetics; Amyotrophic Lateral Sclerosis - pathology; Antibodies; Binding proteins; C9orf72 Protein; Cell Cycle Proteins; Chemical properties; Colorimetry; Dementia; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Female; FUS protein; Gene Expression Regulation - genetics; Guanine Nucleotide Exchange Factors - metabolism; Humans; Immunohistochemistry; Immunoprecipitation; Inclusion bodies; Intermediate filament proteins; Intermediate Filament Proteins - metabolism; Localization; Male; Medicine; Medicine & Public Health; Membrane Glycoproteins - metabolism; Membrane Transport Proteins; Metabolism; Microscopy, Confocal; Molecular weight; Motor neurons; Motor Neurons - metabolism; Mutation; Mutation - genetics; Nerve Tissue Proteins - metabolism; Neurofilament Proteins - metabolism; Neurofilaments; Neurons; Neurosciences; Nucleotides; Organic Chemicals; Original Paper; Pathology; Peripherin; Peripherins; Protein binding; Proteins; Proteins - genetics; Proteins - metabolism; RNA; RNA-binding protein; RNA-Binding Protein FUS - genetics; RNA-Binding Protein FUS - metabolism; RNA-Binding Proteins - metabolism; Sequestosome-1 Protein; Spinal cord; Spinal Cord - pathology; Superoxide dismutase; Superoxide Dismutase - genetics; Superoxide Dismutase - metabolism; Superoxide Dismutase-1; Transcription Factor TFIIIA - metabolism; Ubiquitin
• ISSN: 0001-6322; 1432-0533
• DOI: 10.1007/s00401-012-1035-z

While the pathogenesis of amyotrophic lateral sclerosis (ALS) remains to be clearly delineated, there is mounting evidence that altered RNA metabolism is a commonality amongst several of the known genetic variants of the disease. In this study, we evaluated the expression of 10 ALS-associated proteins in spinal motor neurons (MNs) in ALS patients with mutations in C9orf72 (C9orf72 GGGGCC -ALS; n  = 5), SOD1 ( mt SOD1-ALS; n  = 9), FUS/TLS ( mt FUS/TLS-ALS; n  = 2), or TARDBP ( mt TDP-43-ALS; n  = 2) and contrasted these to cases of sporadic ALS ( s ALS; n  = 4) and familial ALS without known mutations ( f ALS; n  = 2). We performed colorimetric immunohistochemistry (IHC) using antibodies against TDP-43, FUS/TLS, SOD1, C9orf72, ubiquitin, sequestosome 1 (p62), optineurin, phosphorylated high molecular weight neurofilament, peripherin, and Rho-guanine nucleotide exchange factor (RGNEF). We observed that RGNEF-immunoreactive neuronal cytoplasmic inclusions (NCIs) can co-localize with TDP-43, FUS/TLS and p62 within spinal MNs. We confirmed their capacity to interact by co-immunoprecipitations. We also found that mt SOD1-ALS cases possess a unique IHC signature, including the presence of C9orf72-immunoreactive diffuse NCIs, which allows them to be distinguished from other variants of ALS at the level of light microscopy. These findings support the hypothesis that alterations in RNA metabolism are a core pathogenic pathway in ALS. We also conclude that routine IHC-based analysis of spinal MNs may aid in the identification of families not previously suspected to harbor SOD1 mutations.