Quantitative analysis and clinico-pathological correlations of different dipeptide repeat protein pathologies in C9ORF72 mutation carriers
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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.
KeywordsAntisense Transcript Motor Neuron Disease Lower Motor Neuron Dystrophic Neurites Neuronal Cytoplasmic Inclusion
We would like to thank Margaret Luk, Katrin Trautmann and Manuel Gödan for their excellent technical assistance. This work was supported by the German Helmholtz Association (VH-VI-510 and W2/W3-036, MN), the Canadian Institutes of Health Research (74580, IRM), the Pacific Alzheimer’s Research Foundation (C06-01, IRM), and the European Unions’s Seventh Framework Program (FP7/2014-2019 Grant 617198, DE).
- 2.Boeve BF, Boylan KB, Graff-Radford NR, DeJesus-Hernandez M, Knopman DS, Pedraza O et al (2012) Characterization of frontotemporal dementia and/or amyotrophic lateral sclerosis associated with the GGGGCC repeat expansion in C9ORF72. Brain 135:765–783. doi: 10.1093/brain/aws004 PubMedCentralCrossRefPubMedGoogle Scholar
- 6.Davidson YS, Barker H, Robinson AC, Thompson JC, Harris J, Troakes C et al (2014) Brain distribution of dipeptide repeat proteins in frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9ORF72. Acta Neuropathol Commun 2:70. doi: 10.1186/2051-5960-2-70 PubMedCentralCrossRefPubMedGoogle Scholar
- 8.Gendron TF, Bieniek KF, Zhang YJ, Jansen-West K, Ash PE, Caulfield T et al (2013) Antisense transcripts of the expanded C9ORF72 hexanucleotide repeat form nuclear RNA foci and undergo repeat-associated non-ATG translation in c9FTD/ALS. Acta Neuropathol 126:829–844. doi: 10.1007/s00401-013-1192-8 PubMedCentralCrossRefPubMedGoogle Scholar
- 10.Gijselinck I, Van Langenhove T, van der Zee J, Sleegers K, Philtjens S, Kleinberger G et al (2012) A C9orf72 promoter repeat expansion in a Flanders–Belgian cohort with disorders of the frontotemporal lobar degeneration–amyotrophic lateral sclerosis spectrum: a gene identification study. Lancet Neurol 11:54–65. doi: 10.1016/S1474-4422(11)70261-7 CrossRefPubMedGoogle Scholar
- 11.Gomez-Deza J, Lee YB, Troakes C, Nolan M, Al-Sarraj S, Gallo JM et al (2015) Dipeptide repeat protein inclusions are rare in the spinal cord and almost absent from motor neurons in C9ORF72 mutant amyotrophic lateral sclerosis and are unlikely to cause their degeneration. Acta Neuropathol Commun 3:38. doi: 10.1186/s40478-015-0218-y PubMedCentralCrossRefPubMedGoogle Scholar
- 22.Mann DM, Rollinson S, Robinson A, Bennion Callister J, Thompson JC, Snowden JS et al (2013) Dipeptide repeat proteins are present in the p62 positive inclusions in patients with frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9ORF72. Acta Neuropathol Commun 1:68. doi: 10.1186/2051-5960-1-68 PubMedCentralCrossRefPubMedGoogle Scholar
- 29.Murray ME, Dejesus-Hernandez M, Rutherford NJ, Baker M, Duara R, Graff-Radford NR et al (2011) Clinical and neuropathologic heterogeneity of c9FTD/ALS associated with hexanucleotide repeat expansion in C9ORF72. Acta Neuropathol 122:673–690. doi: 10.1007/s00401-011-0907-y PubMedCentralCrossRefPubMedGoogle Scholar
- 37.Stewart H, Rutherford NJ, Briemberg H, Krieger C, Cashman N, Fabros M et al (2012) Clinical and pathological features of amyotrophic lateral sclerosis caused by mutation in the C9ORF72 gene on chromosome 9p. Acta Neuropathol 123:409–417. doi: 10.1007/s00401-011-0937-5 PubMedCentralCrossRefPubMedGoogle Scholar
- 41.Troakes C, Maekawa S, Wijesekera L, Rogelj B, Siklos L, Bell C et al (2012) An MND/ALS phenotype associated with C9orf72 repeat expansion: abundant p62-positive, TDP-43-negative inclusions in cerebral cortex, hippocampus and cerebellum but without associated cognitive decline. Neuropathology 32:505–514. doi: 10.1111/j.1440-1789.2011.01286.x CrossRefPubMedGoogle Scholar
- 42.Wen X, Tan W, Westergard T, Krishnamurthy K, Markandaiah SS, Shi Y et al (2014) Antisense proline-arginine RAN dipeptides linked to C9ORF72-ALS/FTD form toxic nuclear aggregates that initiate in vitro and in vivo neuronal death. Neuron 84:1213–1225. doi: 10.1016/j.neuron.2014.12.010 CrossRefPubMedGoogle Scholar