title: Co-aggregation of RNA binding proteins in ALS spinal motor neurons: evidence of a common pathogenic mechanism.
abstract: 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 (mtSOD1-ALS; n = 9), FUS/TLS (mtFUS/TLS-ALS; n = 2), or TARDBP (mtTDP-43-ALS; n = 2) and contrasted these to cases of sporadic ALS (sALS; n = 4) and familial ALS without known mutations (fALS; 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 mtSOD1-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.
authors.affiliation: Department of Pathology, Western University, London, ON, Canada.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Keller
authors.forename: Kathryn
authors.initials: K
authors.lastname: Volkening
authors.forename: Cristian A
authors.initials: CA
authors.lastname: Droppelmann
authors.forename: Lee Cyn
authors.initials: LC
authors.lastname: Ang
authors.forename: Rosa
authors.initials: R
authors.lastname: Rademakers
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Strong
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000690:Amyotrophic Lateral Sclerosis / Q000145:classification / Q000235:genetics / Q000473:pathology*; D000073885:C9orf72 Protein; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007381:Intermediate Filament Proteins / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D018613:Microscopy, Confocal; D009046:Motor Neurons / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D009930:Organic Chemicals; D064531:Peripherins; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D034702:RNA-Binding Protein FUS / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D000071456:Sequestosome-1 Protein; D013116:Spinal Cord / Q000473:pathology*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D035582:Transcription Factor TFIIIA / Q000378:metabolism
chemical_list: C551174:ARHGEF28 protein, human; D048868:Adaptor Proteins, Signal Transducing; D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D007381:Intermediate Filament Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; C409460:OPTN protein, human; D009930:Organic Chemicals; C578994:PRPH protein, human; D064531:Peripherins; D011506:Proteins; D034702:RNA-Binding Protein FUS; D016601:RNA-Binding Proteins; C000606290:SOD1 protein, human; C099718:SQSTM1 protein, human; C103533:SYTO 14; D000071456:Sequestosome-1 Protein; D035582:Transcription Factor TFIIIA; C051774:neurofilament protein H; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1