title: Distribution of dipeptide repeat proteins in cellular models and C9orf72 mutation cases suggests link to transcriptional silencing.
abstract: A massive expansion of a GGGGCC repeat upstream of the C9orf72 coding region is the most common known cause of amyotrophic lateral sclerosis and frontotemporal dementia. Despite its intronic localization and lack of a canonical start codon, both strands are translated into aggregating dipeptide repeat (DPR) proteins: poly-GA, poly-GP, poly-GR, poly-PR and poly-PA. To address conflicting findings on the predominant toxicity of the different DPR species in model systems, we compared the expression pattern of the DPR proteins in rat primary neurons and postmortem brain and spinal cord of C9orf72 mutation patients. Only poly-GA overexpression closely mimicked the p62-positive neuronal cytoplasmic inclusions commonly observed for all DPR proteins in patients. In contrast, overexpressed poly-GR and poly-PR formed nucleolar p62-negative inclusions. In patients, most of the less common neuronal intranuclear DPR inclusions were para-nucleolar and p62 positive. Neuronal nucleoli in C9orf72 cases showed normal size and morphology regardless of the presence of poly-GR and poly-PR inclusions arguing against widespread nucleolar stress, reported in cellular models. Colocalization of para-nucleolar DPR inclusions with heterochromatin and a marker of transcriptional repression (H3K9me2) indicates a link to gene transcription. In contrast, we detected numerous intranuclear DPR inclusions not associated with nucleolar structures in ependymal and subependymal cells. In patients, neuronal inclusions of poly-GR, poly-GP and the poly-GA interacting protein Unc119 were less abundant than poly-GA inclusions, but showed similar regional and subcellular distribution. Regardless of neurodegeneration, all inclusions were most abundant in neocortex, hippocampus and thalamus, with few inclusions in brain stem and spinal cord. In the granular cell layer of the cerebellum, poly-GA and Unc119 inclusions were significantly more abundant in cases with FTLD than in cases with MND and FTLD/MND. Poly-PR inclusions were rare throughout the brain but significantly more abundant in the CA3/4 region of FTLD cases than in MND cases. Thus, although DPR distribution is not correlated with neurodegeneration spatially, it correlates with neuropathological subtypes.
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Schludi
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.
authors.forename: Stephanie
authors.initials: S
authors.lastname: May
authors.affiliation: Institute of Virology, Saarland University Medical School, 66421, Homburg, Germany.
authors.forename: Friedrich A
authors.initials: FA
authors.lastname: Grässer
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Rentzsch
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.|Institute of Molecular Immunology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Marchioninistr. 25, 81377, Munich, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.|Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University, 80336, Munich, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Küpper
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany.|Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University, 80336, Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Klopstock
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany. thomas.arzberger@med.uni-muenchen.de.|Center for Neuropathology and Prion Research, Ludwig-Maximilians-University Munich, Feodor-Lynen-Str. 23, 81377, Munich, Germany. thomas.arzberger@med.uni-muenchen.de.|Department of Psychiatry and Psychotherapy, Ludwig-Maximilians University Munich, Nußbaumstraße 7, 80336, Munich, Germany. thomas.arzberger@med.uni-muenchen.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Arzberger
authors.affiliation: German Center for Neurodegenerative Diseases (DZNE), Feodor-Lynen-Str. 17, 81337, Munich, Germany. dieter.edbauer@dzne.de.|Munich Cluster of Systems Neurology (SyNergy), Munich, Germany. dieter.edbauer@dzne.de.|Institute for Metabolic Biochemistry, Ludwig-Maximilians University Munich, 81377, Munich, Germany. dieter.edbauer@dzne.de.
authors.forename: Dieter
authors.initials: D
authors.lastname: Edbauer
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000328:Adult; D000368:Aged; D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology; D000073885:C9orf72 Protein; D002466:Cell Nucleolus / Q000378:metabolism / Q000473:pathology; D015331:Cohort Studies; D042622:DNA Repeat Expansion; D057174:Frontotemporal Lobar Degeneration / Q000150:complications / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020868:Gene Silencing; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000150:complications / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009457:Neuroglia / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D051381:Rats; D013116:Spinal Cord / Q000378:metabolism / Q000473:pathology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins; C098032:UNC119 protein, human
keywords: ALS; C9orf72; DPR inclusions; FTLD; Neurotoxicity; Repeat disorders