title: Reduced C9orf72 protein levels in frontal cortex of amyotrophic lateral sclerosis and frontotemporal degeneration brain with the C9ORF72 hexanucleotide repeat expansion.
abstract: An intronic G(4)C(2) hexanucleotide repeat expansion in C9ORF72 is a major cause of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Several mechanisms including RNA toxicity, repeat-associated non-AUG translation mediated dipeptide protein aggregates, and haploinsufficiency of C9orf72 have been implicated in the molecular pathogenesis of this disorder. The aims of this study were to compare the use of two different Southern blot probes for detection of repeat expansions in an amyotrophic lateral sclerosis and frontotemporal lobar degeneration pathological cohort and to determine the levels of C9orf72 transcript variants and protein isoforms in patients versus control subjects. Our Southern blot studies identified smaller repeat expansions (250-1800 bp) that were only detectable with the flanking probe highlighting the potential for divergent results using different Southern blotting protocols that could complicate genotype-phenotype correlation studies. Further, we characterize a new C9orf72 antibody and show for the first time decreased C9orf72 protein levels in the frontal cortex from patients with a pathological hexanucleotide repeat expansion. These data suggest that a reduction in C9orf72 protein may be a consequence of the disease.
authors.affiliation: Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cathays, Cardiff, UK. Electronic address: waitea@cf.ac.uk.
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Waite
authors.affiliation: Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Dirk
authors.initials: D
authors.lastname: Bäumer
authors.affiliation: Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Simon
authors.initials: S
authors.lastname: East
authors.affiliation: Department of Pathology, School of Medicine, Cardiff University, Cardiff, UK.
authors.forename: James
authors.initials: J
authors.lastname: Neal
authors.affiliation: Department of Clinical Neuroscience, UCL Institute of Neurology, Royal Free Hospital, London, UK.
authors.forename: Huw R
authors.initials: HR
authors.lastname: Morris
authors.affiliation: Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Olaf
authors.initials: O
authors.lastname: Ansorge
authors.affiliation: Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, Cathays, Cardiff, UK.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Blake
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics*; D000073885:C9orf72 Protein; D015331:Cohort Studies; D042622:DNA Repeat Expansion / Q000235:genetics*; D005625:Frontal Lobe / Q000378:metabolism; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics*; D056726:Genetic Association Studies / Q000379:methods; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D010641:Phenotype; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins
keywords: Amyotrophic lateral sclerosis; C9orf72; Frontotemporal dementia; Frontotemporal lobar degeneration; Repeat expansion; Southern blotting