title: Quantitative analysis and clinico-pathological correlations of different dipeptide repeat protein pathologies in C9ORF72 mutation carriers.
abstract: Hexanucleotide repeat expansion in C9ORF72 is the most common genetic cause of frontotemporal dementia and motor neuron disease. One consequence of the mutation is the formation of different potentially toxic polypeptides composed of dipeptide repeats (DPR) (poly-GA, -GP, -GR, -PA, -PR) generated by repeat-associated non-ATG (RAN) translation. While previous studies focusing on poly-GA pathology have failed to detect any clinico-pathological correlations in C9ORF72 mutation cases, recent data from animal and cell culture models suggested that it may be only specific DPR species that are toxic and only when accumulated in certain intracellular compartments. Therefore, we performed a systematic clinico-pathological correlative analysis with counting of actual numbers of distinct types of inclusion (neuronal cytoplasmic and intranuclear inclusions, dystrophic neurites) for each DPR protein in relevant brain regions (premotor cortex, lower motor neurons) in a cohort of 35 C9ORF72 mutation cases covering the clinical spectrum from those with pure MND, mixed FTD/MND and pure FTD. While each DPR protein pathology had a similar pattern of anatomical distribution, the total amount of inclusions for each DPR protein varied remarkably (poly-GA > GP > GR > PR/PA), indicating that RAN translation seems to be more effective from sense than from antisense transcripts. Importantly, with the exception of moderate associations for the amount of poly-GA-positive dystrophic neurites with degeneration in the frontal cortex and total burden of poly-GA pathology with disease onset, no relationship was identified for any other DPR protein pathology with degeneration or phenotype. Biochemical analysis revealed a close correlation between insoluble DPR protein species and numbers of visible inclusions, while we did not find any evidence for the presence of soluble DPR protein species. Thus, overall our findings strongly argue against a role of DPR protein aggregation as major and exclusive pathomechanism in C9ORF72 pathogenesis. However, this does not exclude that DPR protein formation might be essential in C9ORF72 pathogenesis in interplay with other consequences associated with the C9ORF72 repeat expansion.
authors.affiliation: Department of Pathology, University of British Columbia and Vancouver General Hospital, Vancouver, Canada.
authors.forename: Ian R A
authors.initials: IR
authors.lastname: Mackenzie
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Otfried-Müllerstr. 23, 72076, Tübingen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Frick
authors.affiliation: Institute of Virology, Saarland University Medical School, Homburg, Germany.
authors.forename: Friedrich A
authors.initials: FA
authors.lastname: Grässer
authors.affiliation: Department of Neuroscience, Mayo Clinic Florida, Jacksonville, USA.
authors.forename: Tania F
authors.initials: TF
authors.lastname: Gendron
authors.affiliation: Department of Neuroscience, Mayo Clinic Florida, Jacksonville, USA.
authors.forename: Leonard
authors.initials: L
authors.lastname: Petrucelli
authors.affiliation: Department of Medicine (Neurology), Brain Research Centre, University of British Columbia, Vancouver, Canada.
authors.forename: Neil R
authors.initials: NR
authors.lastname: Cashman
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.|Institute for Metabolic Biochemistry, Ludwig-Maximilians University Munich, Munich, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Edbauer
authors.affiliation: Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.|Institute of Molecular Immunology, Helmholtz Zentrum München, Munich, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Rostock, Germany.|Department of Neurology, University of Rostock, Rostock, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Prudlo
authors.affiliation: Department of Neuropathology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Dirk
authors.initials: D
authors.lastname: Troost
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Otfried-Müllerstr. 23, 72076, Tübingen, Germany. manuela.neumann@med.uni-tuebingen.de.|Department of Neuropathology, University of Tübingen, Tübingen, Germany. manuela.neumann@med.uni-tuebingen.de.
authors.forename: Manuela
authors.initials: M
authors.lastname: Neumann
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000378:metabolism / Q000473:pathology; D000073885:C9orf72 Protein; D042622:DNA Repeat Expansion; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D057180:Frontotemporal Dementia / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D006579:Heterozygote; D006801:Humans; D007002:Hypoglossal Nerve; D015151:Immunoblotting; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D011506:Proteins / Q000235:genetics*; D012720:Severity of Illness Index; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology; D014015:Tissue Banks
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D004268:DNA-Binding Proteins; D011506:Proteins; C000598624:TARDBP protein, human