Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

C9orf72-mediated ALS and FTD: multiple pathways to disease

Abstract

The discovery that repeat expansions in the C9orf72 gene are a frequent cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) has revolutionized our understanding of these diseases. Substantial headway has been made in characterizing C9orf72-mediated disease and unravelling its underlying aetiopathogenesis. Three main disease mechanisms have been proposed: loss of function of the C9orf72 protein and toxic gain of function from C9orf72 repeat RNA or from dipeptide repeat proteins produced by repeat-associated non-ATG translation. Several downstream processes across a range of cellular functions have also been implicated. In this article, we review the pathological and mechanistic features of C9orf72-associated FTD and ALS (collectively termed C9FTD/ALS), the model systems used to study these conditions, and the probable initiators of downstream disease mechanisms. We suggest that a combination of upstream mechanisms involving both loss and gain of function and downstream cellular pathways involving both cell-autonomous and non-cell-autonomous effects contributes to disease progression.

Key points

  • Rapid progress has been made in the understanding of how repeat expansions in C9orf72 cause C9orf72-associated frontotemporal dementia and/or amyotrophic lateral sclerosis (C9FTD/ALS).

  • Both loss of function of C9orf72 and gain of toxic function of the repeats are implicated in C9FTD/ALS.

  • A range of new models, including mice, Drosophila and patient neurons, have provided new insights into the disease mechanisms.

  • Several cellular pathways are affected in C9FTD/ALS and could provide new options for treatment.

  • Targeted therapeutic strategies against the repeats themselves are the most advanced and are progressing towards clinical trials.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: C9orf72 structure, transcript variants and protein isoforms.
Fig. 2: Dipeptide repeat proteins.
Fig. 3: C9FTD/ALS neuropathology.
Fig. 4: Cellular processes implicated in C9FTD/ALS.

References

  1. 1.

    DeJesus-Hernandez, M. et al. Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. Neuron 72, 245–256 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  2. 2.

    Renton, A. E. et al. A hexanucleotide repeat expansion in C9ORF72 is the cause of chromosome 9p21-linked ALS–FTD. Neuron 72, 257–268 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  3. 3.

    Majounie, E. et al. Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: a cross-sectional study. Lancet Neurol. 11, 323–330 (2012).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  4. 4.

    Woollacott, I. O. & Mead, S. The C9ORF72 expansion mutation: gene structure, phenotypic and diagnostic issues. Acta Neuropathol. 127, 319–332 (2014).

    PubMed  Article  CAS  Google Scholar 

  5. 5.

    Rutherford, N. J. et al. Length of normal alleles of C9ORF72 GGGGCC repeat do not influence disease phenotype. Neurobiol. Aging 33, 2950.e5–2950.e7 (2012).

    Article  CAS  Google Scholar 

  6. 6.

    Harms, M. B. et al. Lack of C9ORF72 coding mutations supports a gain of function for repeat expansions in amyotrophic lateral sclerosis. Neurobiol. Aging 34, 2234.e13–2234.e19 (2013).

    Article  CAS  Google Scholar 

  7. 7.

    van der Zee, J. et al. A pan-European study of the C9orf72 repeat associated with FTLD: geographic prevalence, genomic instability, and intermediate repeats. Hum. Mutat. 34, 363–373 (2013).

    PubMed  Article  CAS  Google Scholar 

  8. 8.

    Beck, J. et al. Large C9orf72 hexanucleotide repeat expansions are seen in multiple neurodegenerative syndromes and are more frequent than expected in the UK population. Am. J. Hum. Genet. 92, 345–353 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  9. 9.

    Suh, E. et al. Semi-automated quantification of C9orf72 expansion size reveals inverse correlation between hexanucleotide repeat number and disease duration in frontotemporal degeneration hexanucleotide repeat expansions. Acta Neuropathol. 130, 363–372 (2015).

    Article  CAS  Google Scholar 

  10. 10.

    van Blitterswijk, M. et al. Association between repeat sizes and clinical and pathological characteristics in carriers of C9ORF72 repeat expansions (Xpansize-72): a cross-sectional cohort study. Lancet Neurol. 12, 978–988 (2013).

    PubMed  Article  CAS  Google Scholar 

  11. 11.

    Mizielinska, S. et al. C9orf72 frontotemporal lobar degeneration is characterised by frequent neuronal sense and antisense RNA foci. Acta Neuropathol. 126, 845–857 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  12. 12.

    Donnelly, C. J. et al. RNA toxicity from the ALS/FTD C9ORF72 expansion is mitigated by antisense intervention. Neuron 80, 415–428 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  13. 13.

    Lagier-Tourenne, C. et al. Targeted degradation of sense and antisense C9orf72 RNA foci as therapy for ALS and frontotemporal degeneration. Proc. Natl Acad. Sci. USA 110, E4530–E4539 (2013).

    PubMed  Article  CAS  Google Scholar 

  14. 14.

    Zu, T. et al. RAN proteins and RNA foci from antisense transcripts in C9ORF72 ALS and frontotemporal dementia. Proc. Natl Acad. Sci. USA 110, E4968–E4977 (2013).

    PubMed  Article  CAS  Google Scholar 

  15. 15.

    Gendron, T. F. et al. 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 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  16. 16.

    Mori, K. et al. The C9orf72 GGGGCC repeat is translated into aggregating dipeptide-repeat proteins in FTLD/ALS. Science 339, 1335–1338 (2013).

    Google Scholar 

  17. 17.

    Ash, P. E. et al. Unconventional translation of C9ORF72 GGGGCC expansion generates insoluble polypeptides specific to c9FTD/ALS. Neuron 77, 639–646 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  18. 18.

    Mori, K. et al. Bidirectional transcripts of the expanded C9orf72 hexanucleotide repeat are translated into aggregating dipeptide repeat proteins. Acta Neuropathol. 126, 881–893 (2013).

    PubMed  Article  CAS  Google Scholar 

  19. 19.

    Rohrer, J. D. et al. C9orf72 expansions in frontotemporal dementia and amyotrophic lateral sclerosis. Lancet Neurol. 14, 291–301 (2015).

    PubMed  Article  CAS  Google Scholar 

  20. 20.

    Renton, A. E., Chio, A. & Traynor, B. J. State of play in amyotrophic lateral sclerosis genetics. Nat. Neurosci. 17, 17–23 (2014).

    PubMed  Article  CAS  Google Scholar 

  21. 21.

    Gami, P. et al. A 30-unit hexanucleotide repeat expansion in C9orf72 induces pathological lesions with dipeptide-repeat proteins and RNA foci, but not TDP-43 inclusions and clinical disease. Acta Neuropathol. 130, 599–601 (2015).

    PubMed  Article  Google Scholar 

  22. 22.

    Gijselinck, I. et al. The C9orf72 repeat size correlates with onset age of disease, DNA methylation and transcriptional downregulation of the promoter. Mol. Psychiatry 21, 1112–1124 (2016).

    PubMed  Article  CAS  Google Scholar 

  23. 23.

    Nordin, A. et al. Extensive size variability of the GGGGCC expansion in C9orf72 in both neuronal and non-neuronal tissues in 18 patients with ALS or FTD. Hum. Mol. Genet. 24, 3133–3142 (2015).

    PubMed  Article  CAS  Google Scholar 

  24. 24.

    Fratta, P. et al. Screening a UK amyotrophic lateral sclerosis cohort provides evidence of multiple origins of the C9orf72 expansion. Neurobiol. Aging 36, 546.e1–546.e7 (2015).

    Article  CAS  Google Scholar 

  25. 25.

    Xi, Z. et al. Jump from pre-mutation to pathologic expansion in C9orf72. Am. J. Hum. Genet. 96, 962–970 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  26. 26.

    Neumann, M. et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science 314, 130–133 (2006).

    PubMed  Article  CAS  Google Scholar 

  27. 27.

    Arai, T. et al. TDP-43 is a component of ubiquitin-positive tau-negative inclusions in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Biochem. Biophys. Res. Commun. 351, 602–611 (2006).

    PubMed  Article  CAS  Google Scholar 

  28. 28.

    Ling, S. C., Polymenidou, M. & Cleveland, D. W. Converging mechanisms in ALS and FTD: disrupted RNA and protein homeostasis. Neuron 79, 416–438 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  29. 29.

    Mackenzie, I. R. et al. Dipeptide repeat protein pathology in C9ORF72 mutation cases: clinico-pathological correlations. Acta Neuropathol. 126, 859–879 (2013).

    PubMed  Article  CAS  Google Scholar 

  30. 30.

    Murray, M. E. et al. Clinical and neuropathologic heterogeneity of c9FTD/ALS associated with hexanucleotide repeat expansion in C9ORF72. Acta Neuropathol. 122, 673–690 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  31. 31.

    Hsiung, G. Y. et al. Clinical and pathological features of familial frontotemporal dementia caused by C9ORF72 mutation on chromosome 9p. Brain 135, 709–722 (2012).

    PubMed  PubMed Central  Article  Google Scholar 

  32. 32.

    Mahoney, C. J. et al. Frontotemporal dementia with the C9ORF72 hexanucleotide repeat expansion: clinical, neuroanatomical and neuropathological features. Brain 135, 736–750 (2012).

    PubMed  PubMed Central  Article  Google Scholar 

  33. 33.

    Irwin, D. J. et al. Cognitive decline and reduced survival in C9orf72 expansion frontotemporal degeneration and amyotrophic lateral sclerosis. J. Neurol. Neurosurg. Psychiatry 84, 163–169 (2013).

    PubMed  Article  Google Scholar 

  34. 34.

    DeJesus-Hernandez, M. et al. In-depth clinico-pathological examination of RNA foci in a large cohort of C9ORF72 expansion carriers. Acta Neuropathol. 134, 255–269 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  35. 35.

    Mann, D. M. et al. 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 (2013).

    PubMed  PubMed Central  Article  Google Scholar 

  36. 36.

    Schludi, M. H. et al. Distribution of dipeptide repeat proteins in cellular models and C9orf72 mutation cases suggests link to transcriptional silencing. Acta Neuropathol. 130, 537–555 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  37. 37.

    Davidson, Y. S. et al. Brain distribution of dipeptide repeat proteins in frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9ORF72. Acta Neuropathol. Commun. 2, 70 (2014).

    PubMed  PubMed Central  Article  Google Scholar 

  38. 38.

    Mackenzie, I. R. et al. Quantitative analysis and clinico-pathological correlations of different dipeptide repeat protein pathologies in C9ORF72 mutation carriers. Acta Neuropathol. 130, 845–861 (2015).

    PubMed  Article  CAS  Google Scholar 

  39. 39.

    Davidson, Y. et al. Neurodegeneration in frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9orf72 is linked to TDP-43 pathology and not associated with aggregated forms of dipeptide repeat proteins. Neuropathol. Appl. Neurobiol. 42, 242–254 (2016).

    PubMed  Article  CAS  Google Scholar 

  40. 40.

    Gomez-Deza, J. et al. 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 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  41. 41.

    Liu, E. Y. et al. C9orf72 hypermethylation protects against repeat expansion-associated pathology in ALS/FTD. Acta Neuropathol. 128, 525–541 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  42. 42.

    Wen, X. et al. 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 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  43. 43.

    Gendron, T. F. et al. Cerebellar c9RAN proteins associate with clinical and neuropathological characteristics of C9ORF72 repeat expansion carriers. Acta Neuropathol. 130, 559–573 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  44. 44.

    Saberi, S. et al. Sense-encoded poly-GR dipeptide repeat proteins correlate to neurodegeneration and uniquely co-localize with TDP-43 in dendrites of repeat-expanded C9orf72 amyotrophic lateral sclerosis. Acta Neuropathol. 135, 459–474 (2018).

    PubMed  Article  CAS  Google Scholar 

  45. 45.

    Su, Z. et al. Discovery of a biomarker and lead small molecules to target r(GGGGCC)-associated defects in c9FTD/ALS. Neuron 83, 1043–1050 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  46. 46.

    Gendron, T. F. et al. Poly(GP) proteins are a useful pharmacodynamic marker for C9ORF72-associated amyotrophic lateral sclerosis. Sci. Transl Med. 9, eaai7866 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  47. 47.

    Lehmer, C. et al. Poly-GP in cerebrospinal fluid links C9orf72-associated dipeptide repeat expression to the asymptomatic phase of ALS/FTD. EMBO Mol. Med. 9, 859–868 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  48. 48.

    Balendra, R., Moens, T. G. & Isaacs, A. M. Specific biomarkers for C9orf72 FTD/ALS could expedite the journey towards effective therapies. EMBO Mol. Med. 9, 853–855 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  49. 49.

    Tran, H. et al. Differential toxicity of nuclear RNA foci versus dipeptide repeat proteins in a Drosophila model of C9ORF72 FTD/ALS. Neuron 87, 1207–1214 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  50. 50.

    Rizzu, P. et al. C9orf72 is differentially expressed in the central nervous system and myeloid cells and consistently reduced in C9orf72. MAPT and GRN mutation carriers. Acta Neuropathol. Commun. 4, 37 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  51. 51.

    Ciura, S. et al. Loss of function of C9orf72 causes motor deficits in a zebrafish model of amyotrophic lateral sclerosis. Ann. Neurol. 74, 180–187 (2013).

    PubMed  CAS  Google Scholar 

  52. 52.

    Xi, Z. et al. Hypermethylation of the CpG island near the G4C2 repeat in ALS with a C9orf72 expansion. Am. J. Hum. Genet. 92, 981–989 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  53. 53.

    Almeida, S. et al. Modeling key pathological features of frontotemporal dementia with C9ORF72 repeat expansion in iPSC-derived human neurons. Acta Neuropathol. 126, 385–399 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  54. 54.

    Shi, Y. et al. Haploinsufficiency leads to neurodegeneration in C9ORF72 ALS/FTD human induced motor neurons. Nat. Med. 24, 313–325 (2018).

    PubMed  Article  CAS  PubMed Central  Google Scholar 

  55. 55.

    Gijselinck, I. et al. 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 (2012).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  56. 56.

    Fratta, P. et al. Homozygosity for the C9orf72 GGGGCC repeat expansion in frontotemporal dementia. Acta Neuropathol. 126, 401–409 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  57. 57.

    Belzil, V. V. et al. Reduced C9orf72 gene expression in c9FTD/ALS is caused by histone trimethylation, an epigenetic event detectable in blood. Acta Neuropathol. 126, 895–905 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  58. 58.

    Waite, A. J. et al. Reduced C9orf72 protein levels in frontal cortex of amyotrophic lateral sclerosis and frontotemporal degeneration brain with the C9ORF72 hexanucleotide repeat expansion. Neurobiol. Aging 35, 1779.e5–1779.e13 (2014).

    PubMed  Article  CAS  Google Scholar 

  59. 59.

    van Blitterswijk, M. et al. Novel clinical associations with specific C9ORF72 transcripts in patients with repeat expansions in C9ORF72. Acta Neuropathol. 130, 863–876 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  60. 60.

    Xiao, S. et al. Isoform-specific antibodies reveal distinct subcellular localizations of C9orf72 in amyotrophic lateral sclerosis. Ann. Neurol. 78, 568–583 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  61. 61.

    Haeusler, A. R. et al. C9orf72 nucleotide repeat structures initiate molecular cascades of disease. Nature 507, 195–200 (2014).

    PubMed  Article  CAS  Google Scholar 

  62. 62.

    Niblock, M. et al. Retention of hexanucleotide repeat-containing intron in C9orf72 mRNA: implications for the pathogenesis of ALS/FTD. Acta Neuropathol. Commun. 4, 18 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  63. 63.

    Levine, T. P., Daniels, R. D., Gatta, A. T., Wong, L. H. & Hayes, M. J. The product of C9orf72, a gene strongly implicated in neurodegeneration, is structurally related to DENN Rab-GEFs. Bioinformatics 29, 499–503 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  64. 64.

    Zhang, D., Iyer, L. M., He, F. & Aravind, L. Discovery of novel DENN proteins: implications for the evolution of eukaryotic intracellular membrane structures and human disease. Front. Genet. 3, 283 (2012).

    PubMed  Article  CAS  Google Scholar 

  65. 65.

    Webster, C. P. et al. The C9orf72 protein interacts with Rab1a and the ULK1 complex to regulate initiation of autophagy. EMBO J. 35, 1656–1676 (2016).

    PubMed  Article  CAS  Google Scholar 

  66. 66.

    Sellier, C. et al. Loss of C9ORF72 impairs autophagy and synergizes with polyQ Ataxin-2 to induce motor neuron dysfunction and cell death. EMBO J. 35, 1276–1297 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  67. 67.

    O’Rourke, J. G. et al. C9orf72 is required for proper macrophage and microglial function in mice. Science 351, 1324–1329 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  68. 68.

    Sullivan, P. M. et al. The ALS/FTLD associated protein C9orf72 associates with SMCR8 and WDR41 to regulate the autophagy-lysosome pathway. Acta Neuropathol. Commun. 4, 51 (2016).

    Article  CAS  Google Scholar 

  69. 69.

    Farg, M. A. et al. C9ORF72, implicated in amytrophic lateral sclerosis and frontotemporal dementia, regulates endosomal trafficking. Hum. Mol. Genet. 23, 3579–3595 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  70. 70.

    Yang, M. et al. A C9ORF72/SMCR8-containing complex regulates ULK1 and plays a dual role in autophagy. Sci. Adv. 2, e1601167 (2016).

    PubMed  Article  CAS  Google Scholar 

  71. 71.

    Ugolino, J. et al. Loss of C9orf72 enhances autophagic activity via deregulated mTOR and TFEB signaling. PLoS Genet. 12, e1006443 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  72. 72.

    Amick, J., Roczniak-Ferguson, A. & Ferguson, S. M. C9orf72 binds SMCR8, localizes to lysosomes, and regulates mTORC1 signaling. Mol. Biol. Cell 27, 3040–3051 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  73. 73.

    Blokhuis, A. M. et al. Comparative interactomics analysis of different ALS-associated proteins identifies converging molecular pathways. Acta Neuropathol. 132, 175–196 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  74. 74.

    Jung, J. et al. Multiplex image-based autophagy RNAi screening identifies SMCR8 as ULK1 kinase activity and gene expression regulator. eLife 6, e23063 (2017).

    PubMed  PubMed Central  Google Scholar 

  75. 75.

    Freischmidt, A. et al. Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia. Nat. Neurosci. 18, 631–636 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  76. 76.

    Elden, A. C. et al. Ataxin-2 intermediate-length polyglutamine expansions are associated with increased risk for ALS. Nature 466, 1069–1075 (2010).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  77. 77.

    Aoki, Y. et al. C9orf72 and RAB7L1 regulate vesicle trafficking in amyotrophic lateral sclerosis and frontotemporal dementia. Brain 140, 887–897 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  78. 78.

    Imamura, K. et al. The Src/c–Abl pathway is a potential therapeutic target in amyotrophic lateral sclerosis. Sci. Transl Med. 9, eaaf3962 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  79. 79.

    Selvaraj, B. T. et al. C9ORF72 repeat expansion causes vulnerability of motor neurons to Ca2+-permeable AMPA receptor-mediated excitotoxicity. Nat. Commun. 9, 347 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  80. 80.

    Suzuki, N. et al. The mouse C9ORF72 ortholog is enriched in neurons known to degenerate in ALS and FTD. Nat. Neurosci. 16, 1725–1727 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  81. 81.

    Koppers, M. et al. C9orf72 ablation in mice does not cause motor neuron degeneration or motor deficits. Ann. Neurol. 78, 426–438 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  82. 82.

    Jiang, J. et al. Gain of toxicity from ALS/FTD-linked repeat expansions in C9ORF72 Is alleviated by antisense oligonucleotides targeting GGGGCC-containing RNAs. Neuron 90, 535–550 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  83. 83.

    Atanasio, A. et al. C9orf72 ablation causes immune dysregulation characterized by leukocyte expansion, autoantibody production, and glomerulonephropathy in mice. Sci. Rep. 6, 23204 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  84. 84.

    Ferguson, R., Serafeimidou-Pouliou, E. & Subramanian, V. Dynamic expression of the mouse orthologue of the human amyotropic lateral sclerosis associated gene C9orf72 during central nervous system development and neuronal differentiation. J. Anat. 229, 871–891 (2016).

    PubMed  PubMed Central  Article  Google Scholar 

  85. 85.

    Sudria-Lopez, E. et al. Full ablation of C9orf72 in mice causes immune system-related pathology and neoplastic events but no motor neuron defects. Acta Neuropathol. 132, 145–147 (2016).

    PubMed  Article  CAS  Google Scholar 

  86. 86.

    Burberry, A. et al. Loss-of-function mutations in the C9ORF72 mouse ortholog cause fatal autoimmune disease. Sci. Transl Med. 8, 347ra93 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  87. 87.

    Komatsu, M. et al. Loss of autophagy in the central nervous system causes neurodegeneration in mice. Nature 441, 880–884 (2006).

    PubMed  Article  Google Scholar 

  88. 88.

    Hara, T. et al. Suppression of basal autophagy in neural cells causes neurodegenerative disease in mice. Nature 441, 885–889 (2006).

    PubMed  Article  Google Scholar 

  89. 89.

    Robberecht, W. & Philips, T. The changing scene of amyotrophic lateral sclerosis. Nat. Rev. Neurosci. 14, 248–264 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  90. 90.

    Fratta, P. et al. C9orf72 hexanucleotide repeat associated with amyotrophic lateral sclerosis and frontotemporal dementia forms RNA G-quadruplexes. Sci. Rep. 2, 1016 (2012).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  91. 91.

    Reddy, K., Zamiri, B., Stanley, S. Y., Macgregor, R. B. Jr & Pearson, C. E. The disease-associated r(GGGGCC)n repeat from the C9orf72 gene forms tract length-dependent uni- and multimolecular RNA G-quadruplex structures. J. Biol. Chem. 288, 9860–9866 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  92. 92.

    Zhou, B. et al. Characterizations of distinct parallel and antiparallel G-quadruplexes formed by two-repeat ALS and FTD related GGGGCC sequence. Sci. Rep. 8, 2366 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  93. 93.

    Vatovec, S., Kovanda, A. & Rogelj, B. Unconventional features of C9ORF72 expanded repeat in amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Neurobiol. Aging 35, 2421.e1–2421.e12 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  94. 94.

    Kovanda, A., Zalar, M., Sket, P., Plavec, J. & Rogelj, B. Anti-sense DNA d(GGCCCC)n expansions in C9ORF72 form i-motifs and protonated hairpins. Sci. Rep. 5, 17944 (2015).

    PubMed  Article  CAS  Google Scholar 

  95. 95.

    Zhang, Y., Roland, C. & Sagui, C. Structure and dynamics of DNA and RNA double helices obtained from the GGGGCC and CCCCGG hexanucleotide repeats that are the hallmark of C9FTD/ALS diseases. ACS Chem. Neurosci. 8, 578–591 (2017).

    PubMed  PubMed Central  Article  Google Scholar 

  96. 96.

    Zamiri, B. et al. Stress-induced acidification may contribute to formation of unusual structures in C9orf72-repeats. Biochim. Biophys. Acta 1862, 1482–1491 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  97. 97.

    Haeusler, A. R., Donnelly, C. J. & Rothstein, J. D. The expanding biology of the C9orf72 nucleotide repeat expansion in neurodegenerative disease. Nat. Rev. Neurosci. 17, 383–395 (2016).

    PubMed  Article  CAS  Google Scholar 

  98. 98.

    Mackenzie, I. R. The role of dipeptide-repeat protein pathology in C9orf72 mutation cases. Neuropathol. Appl. Neurobiol. 42, 217–219 (2016).

    PubMed  Article  CAS  Google Scholar 

  99. 99.

    Baborie, A. et al. Accumulation of dipeptide repeat proteins predates that of TDP-43 in frontotemporal lobar degeneration associated with hexanucleotide repeat expansions in C9ORF72 gene. Neuropathol. Appl. Neurobiol. 41, 601–612 (2015).

    PubMed  Article  CAS  Google Scholar 

  100. 100.

    Mann, D. M. Dipeptide repeat protein toxicity in frontotemporal lobar degeneration and in motor neurone disease associated with expansions in C9ORF72 — a cautionary note. Neurobiol. Aging 36, 1224–1226 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  101. 101.

    Mattsson, N., Schott, J. M., Hardy, J., Turner, M. R. & Zetterberg, H. Selective vulnerability in neurodegeneration: insights from clinical variants of Alzheimer’s disease. J. Neurol. Neurosurg. Psychiatry 87, 1000–1004 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  102. 102.

    Zhang, K. et al. The C9orf72 repeat expansion disrupts nucleocytoplasmic transport. Nature 525, 56–61 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  103. 103.

    Mori, K. et al. Reduced hnRNPA3 increases C9orf72 repeat RNA levels and dipeptide-repeat protein deposition. EMBO Rep. 17, 1314–1325 (2016).

    Article  CAS  Google Scholar 

  104. 104.

    Yamakawa, M. et al. Characterization of the dipeptide repeat protein in the molecular pathogenesis of c9FTD/ALS. Hum. Mol. Genet. 24, 1630–1645 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  105. 105.

    Proudfoot, M. et al. Early dipeptide repeat pathology in a frontotemporal dementia kindred with C9ORF72 mutation and intellectual disability. Acta Neuropathol. 127, 451–458 (2014).

    PubMed  Article  CAS  Google Scholar 

  106. 106.

    Vatsavayai, S. C. et al. Timing and significance of pathological features in C9orf72 expansion-associated frontotemporal dementia. Brain 139, 3202–3216 (2016).

    PubMed  Article  CAS  Google Scholar 

  107. 107.

    Xu, Z. et al. Expanded GGGGCC repeat RNA associated with amyotrophic lateral sclerosis and frontotemporal dementia causes neurodegeneration. Proc. Natl Acad. Sci. USA 110, 7778–7783 (2013).

    PubMed  Article  CAS  Google Scholar 

  108. 108.

    Swinnen, B. et al. A zebrafish model for C9orf72 ALS reveals RNA toxicity as a pathogenic mechanism. Acta Neuropathol. 135, 427–443 (2018).

    PubMed  Article  CAS  Google Scholar 

  109. 109.

    Moens, T. G. et al. Sense and antisense RNA are not toxic in Drosophila models of C9orf72-associated ALS/FTD. Acta Neuropathol. 135, 445–457 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  110. 110.

    Mizielinska, S. et al. C9orf72 repeat expansions cause neurodegeneration in Drosophila through arginine-rich proteins. Science 345, 1192–1194 (2014).

    PubMed  Article  CAS  Google Scholar 

  111. 111.

    Tao, Z. et al. Nucleolar stress and impaired stress granule formation contribute to C9orf72 RAN translation-induced cytotoxicity. Hum. Mol. Genet. 24, 2426–2441 (2015).

    PubMed  Article  Google Scholar 

  112. 112.

    Kanekura, K. et al. Poly-dipeptides encoded by the C9ORF72 repeats block global protein translation. Hum. Mol. Genet. 25, 1803–1813 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  113. 113.

    Zhang, Y. J. et al. Aggregation-prone c9FTD/ALS poly(GA) RAN-translated proteins cause neurotoxicity by inducing ER stress. Acta Neuropathol. 128, 505–524 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  114. 114.

    May, S. et al. C9orf72 FTLD/ALS-associated Gly–Ala dipeptide repeat proteins cause neuronal toxicity and Unc119 sequestration. Acta Neuropathol. 128, 485–503 (2014).

    PubMed  Article  CAS  Google Scholar 

  115. 115.

    Chang, Y. J., Jeng, U. S., Chiang, Y. L., Hwang, I. S. & Chen, Y. R. The glycine–alanine dipeptide repeat from C9orf72 hexanucleotide expansions forms toxic amyloids possessing cell-to-cell transmission properties. J. Biol. Chem. 291, 4903–4911 (2016).

    PubMed  Article  CAS  Google Scholar 

  116. 116.

    Lee, K. H. et al. C9orf72 dipeptide repeats impair the assembly, dynamics, and function of membrane-less organelles. Cell 167, 774–788.e17 (2016).

    PubMed  PubMed Central  Article  Google Scholar 

  117. 117.

    Freibaum, B. D. et al. GGGGCC repeat expansion in C9orf72 compromises nucleocytoplasmic transport. Nature 525, 129–133 (2015).

    PubMed  Article  Google Scholar 

  118. 118.

    Boeynaems, S. et al. Drosophila screen connects nuclear transport genes to DPR pathology in c9ALS/FTD. Sci. Rep. 6, 20877 (2016).

    PubMed  Article  CAS  Google Scholar 

  119. 119.

    Yang, D. et al. FTD/ALS-associated poly(GR) protein impairs the Notch pathway and is recruited by poly(GA) into cytoplasmic inclusions. Acta Neuropathol. 130, 525–535 (2015).

    PubMed  Article  CAS  Google Scholar 

  120. 120.

    Swaminathan, A. et al. Expression of C9orf72-related dipeptides impairs motor function in a vertebrate model. Hum. Mol. Genet. 27, 1754–1762 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  121. 121.

    Ohki, Y. et al. Glycine–alanine dipeptide repeat protein contributes to toxicity in a zebrafish model of C9orf72 associated neurodegeneration. Mol. Neurodegener. 12, 6 (2017).

    PubMed  Article  CAS  Google Scholar 

  122. 122.

    Zhang, Y. J. et al. C9ORF72 poly(GA) aggregates sequester and impair HR23 and nucleocytoplasmic transport proteins. Nat. Neurosci. 19, 668–677 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  123. 123.

    Schludi, M. H. et al. Spinal poly-GA inclusions in a C9orf72 mouse model trigger motor deficits and inflammation without neuron loss. Acta Neuropathol. 134, 241–254 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  124. 124.

    Moens, T. G., Partridge, L. & Isaacs, A. M. Genetic models of C9orf72: what is toxic? Curr. Opin. Genet. Dev. 44, 92–101 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  125. 125.

    Jovicic, A. et al. Modifiers of C9orf72 dipeptide repeat toxicity connect nucleocytoplasmic transport defects to FTD/ALS. Nat. Neurosci. 18, 1226–1229 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  126. 126.

    Kwon, I. et al. Poly-dipeptides encoded by the C9orf72 repeats bind nucleoli, impede RNA biogenesis, and kill cells. Science 345, 1139–1145 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  127. 127.

    Flores, B. N. et al. Distinct C9orf72-associated dipeptide repeat structures correlate with neuronal toxicity. PLoS ONE 11, e0165084 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  128. 128.

    Baldwin, K. R., Godena, V. K., Hewitt, V. L. & Whitworth, A. J. Axonal transport defects are a common phenotype in Drosophila models of ALS. Hum. Mol. Genet. 25, 2378–2392 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  129. 129.

    Guo, Q. et al. In situ structure of neuronal C9orf72 poly-GA aggregates reveals proteasome recruitment. Cell 172, 696–705.e12 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  130. 130.

    Chew, J. et al. C9ORF72 repeat expansions in mice cause TDP-43 pathology, neuronal loss, and behavioral deficits. Science 348, 1151–1154 (2015).

    PubMed  Article  Google Scholar 

  131. 131.

    Peters, O. M. et al. Human C9ORF72 hexanucleotide expansion reproduces RNA foci and dipeptide repeat proteins but not neurodegeneration in BAC transgenic mice. Neuron 88, 902–909 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  132. 132.

    O’Rourke, J. G. et al. C9orf72 BAC transgenic mice display typical pathologic features of ALS/FTD. Neuron 88, 892–901 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  133. 133.

    Liu, Y. et al. C9orf72 BAC mouse model with motor deficits and neurodegenerative features of ALS/FTD. Neuron 90, 521–534 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  134. 134.

    Kramer, N. J. et al. CRISPR–Cas9 screens in human cells and primary neurons identify modifiers of C9ORF72 dipeptide-repeat-protein toxicity. Nat. Genet. 50, 603–612 (2018).

    PubMed  Article  CAS  Google Scholar 

  135. 135.

    Prpar Mihevc, S. et al. Nuclear trafficking in amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Brain 140, 13–26 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  136. 136.

    Lin, Y. et al. Toxic PR poly-dipeptides encoded by the C9orf72 repeat expansion target LC domain polymers. Cell 167, 789–802.e12 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  137. 137.

    Lagier-Tourenne, C., Polymenidou, M. & Cleveland, D. W. TDP-43 and FUS/TLS: emerging roles in RNA processing and neurodegeneration. Hum. Mol. Genet. 19, R46–R64 (2010).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  138. 138.

    Molliex, A. et al. Phase separation by low complexity domains promotes stress granule assembly and drives pathological fibrillization. Cell 163, 123–133 (2015).

    PubMed  PubMed Central  CAS  Google Scholar 

  139. 139.

    Patel, A. et al. A liquid-to-solid phase transition of the ALS protein FUS accelerated by disease mutation. Cell 162, 1066–1077 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  140. 140.

    Murakami, T. et al. ALS/FTD mutation-induced phase transition of FUS liquid droplets and reversible hydrogels into irreversible hydrogels impairs RNP granule function. Neuron 88, 678–690 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  141. 141.

    Boeynaems, S. et al. Phase separation of C9orf72 dipeptide repeats perturbs stress granule dynamics. Mol. Cell 65, 1044–1055.e5 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  142. 142.

    Zhang, K. et al. Stress granule assembly disrupts nucleocytoplasmic transport. Cell 173, 958–971.e17 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  143. 143.

    Fay, M. M., Anderson, P. J. & Ivanov, P. ALS/FTD-associated C9ORF72 repeat RNA promotes phase transitions in vitro and in cells. Cell Rep. 21, 3573–3584 (2017).

    PubMed  Article  CAS  Google Scholar 

  144. 144.

    Jain, A. & Vale, R. D. RNA phase transitions in repeat expansion disorders. Nature 546, 243–247 (2017).

    PubMed  Article  CAS  PubMed Central  Google Scholar 

  145. 145.

    Rossi, S. et al. Nuclear accumulation of mRNAs underlies G4C2-repeat-induced translational repression in a cellular model of C9orf72 ALS. J. Cell Sci. 128, 1787–1799 (2015).

    PubMed  Article  Google Scholar 

  146. 146.

    Green, K. M. et al. RAN translation at C9orf72-associated repeat expansions is selectively enhanced by the integrated stress response. Nat. Commun. 8, 2005 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  147. 147.

    Bowden, H. A. & Dormann, D. Altered mRNP granule dynamics in FTLD pathogenesis. J. Neurochem. 138 (Suppl. 1), 112–133 (2016).

    PubMed  Article  CAS  Google Scholar 

  148. 148.

    Cheng, W. et al. C9ORF72 GGGGCC repeat-associated non-AUG translation is upregulated by stress through eIF2α phosphorylation. Nat. Commun. 9, 51 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  149. 149.

    Tabet, R. et al. CUG initiation and frameshifting enable production of dipeptide repeat proteins from ALS/FTD C9ORF72 transcripts. Nat. Commun. 9, 152 (2018).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  150. 150.

    Mizielinska, S. et al. Bidirectional nucleolar dysfunction in C9orf72 frontotemporal lobar degeneration. Acta Neuropathol. Commun. 5, 29 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  151. 151.

    Bennion Callister, J., Ryan, S., Sim, J., Rollinson, S. & Pickering-Brown, S. M. Modelling C9orf72 dipeptide repeat proteins of a physiologically relevant size. Hum. Mol. Genet. 25, 5069–5082 (2016).

    PubMed  PubMed Central  Google Scholar 

  152. 152.

    Yin, S. et al. Evidence that C9ORF72 dipeptide repeat proteins associate with U2 snRNP to cause mis-splicing in ALS/FTD patients. Cell Rep. 19, 2244–2256 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  153. 153.

    Lopez-Gonzalez, R. et al. Poly(GR) in C9ORF72-related ALS/FTD compromises mitochondrial function and increases oxidative stress and DNA damage in iPSC-derived motor neurons. Neuron 92, 383–391 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  154. 154.

    Dafinca, R. et al. C9orf72 hexanucleotide expansions are associated with altered ER calcium homeostasis and stress granule formation in iPSC-derived neurons from patients with amyotrophic lateral sclerosis and frontotemporal dementia. Stem Cells 34, 2063–2078 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  155. 155.

    Walker, C. et al. C9orf72 expansion disrupts ATM-mediated chromosomal break repair. Nat. Neurosci. 20, 1225–1235 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  156. 156.

    Farg, M. A., Konopka, A., Ying Soo, K., Ito, D. & Atkin, J. D. The DNA damage response (DDR) is induced by the C9orf72 repeat expansion in amyotrophic lateral sclerosis. Hum. Mol. Genet. 26, 2882–2896 (2017).

    PubMed  Article  CAS  Google Scholar 

  157. 157.

    Sareen, D. et al. Targeting RNA foci in iPSC-derived motor neurons from ALS patients with a C9ORF72 repeat expansion. Sci. Transl Med. 5, 208ra149 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  158. 158.

    Miller, T. M. et al. An antisense oligonucleotide against SOD1 delivered intrathecally for patients with SOD1 familial amyotrophic lateral sclerosis: a phase 1, randomised, first-in-man study. Lancet Neurol. 12, 435–442 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  159. 159.

    Zamiri, B., Reddy, K., Macgregor Jr, R. B. & Pearson, C. E. TMPyP4 porphyrin distorts RNA G-quadruplex structures of the disease-associated r(GGGGCC)n repeat of the C9orf72 gene and blocks interaction of RNA-binding proteins. J. Biol. Chem. 289, 4653–4659 (2014).

    PubMed  Article  CAS  Google Scholar 

  160. 160.

    Simone, R. et al. G-Quadruplex-binding small molecules ameliorate C9orf72 FTD/ALS pathology in vitro and in vivo. EMBO Mol. Med 10, 22–31 (2018).

    PubMed  Article  CAS  Google Scholar 

  161. 161.

    Alniss, H., Zamiri, B., Khalaj, M., Pearson, C. E. & Macgregor, R. B. Jr. Thermodynamic and spectroscopic investigations of TMPyP4 association with guanine- and cytosine-rich DNA and RNA repeats of C9orf72. Biochem. Biophys. Res. Commun. 495, 2410–2417 (2018).

    PubMed  Article  CAS  Google Scholar 

  162. 162.

    Kramer, N. J. et al. Spt4 selectively regulates the expression of C9orf72 sense and antisense mutant transcripts. Science 353, 708–712 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  163. 163.

    Hu, J., Rigo, F., Prakash, T. P. & Corey, D. R. Recognition of c9orf72 mutant RNA by single-stranded silencing RNAs. Nucleic Acid Ther. 27, 87–94 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  164. 164.

    Pinto, B. S. et al. Impeding transcription of expanded microsatellite repeats by deactivated Cas9. Mol. Cell 68, 479–490.e5 (2017).

    PubMed  Article  CAS  Google Scholar 

  165. 165.

    Batra, R. et al. Elimination of toxic microsatellite repeat expansion RNA by RNA-targeting Cas9. Cell 170, 899–912.e10 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  166. 166.

    Schenk, D. et al. Immunization with amyloid-beta attenuates Alzheimer-disease-like pathology in the PDAPP mouse. Nature 400, 173–177 (1999).

    PubMed  Article  CAS  Google Scholar 

  167. 167.

    Asuni, A. A., Boutajangout, A., Quartermain, D. & Sigurdsson, E. M. Immunotherapy targeting pathological tau conformers in a tangle mouse model reduces brain pathology with associated functional improvements. J. Neurosci. 27, 9115–9129 (2007).

    PubMed  Article  CAS  Google Scholar 

  168. 168.

    Boutajangout, A., Ingadottir, J., Davies, P. & Sigurdsson, E. M. Passive immunization targeting pathological phospho-tau protein in a mouse model reduces functional decline and clears tau aggregates from the brain. J. Neurochem. 118, 658–667 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  169. 169.

    Masliah, E. et al. Effects of α-synuclein immunization in a mouse model of Parkinson’s disease. Neuron 46, 857–868 (2005).

    PubMed  Article  CAS  Google Scholar 

  170. 170.

    Masliah, E. et al. Passive immunization reduces behavioral and neuropathological deficits in an alpha-synuclein transgenic model of Lewy body disease. PLoS ONE 6, e19338 (2011).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  171. 171.

    Zhou, Q. et al. Antibodies inhibit transmission and aggregation of C9orf72 poly-GA dipeptide repeat proteins. EMBO Mol. Med. 9, 687–702 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  172. 172.

    Cristofani, R. et al. The small heat shock protein B8 (HSPB8) efficiently removes aggregating species of dipeptides produced in C9ORF72-related neurodegenerative diseases. Cell Stress Chaperones 23, 1–12 (2018).

    PubMed  Article  CAS  Google Scholar 

  173. 173.

    Hautbergue, G. M. et al. SRSF1-dependent nuclear export inhibition of C9ORF72 repeat transcripts prevents neurodegeneration and associated motor deficits. Nat. Commun. 8, 16063 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  174. 174.

    Becker, L. A. et al. Therapeutic reduction of ataxin-2 extends lifespan and reduces pathology in TDP-43 mice. Nature 544, 367–371 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  175. 175.

    Yang, Y. M. et al. A small molecule screen in stem-cell-derived motor neurons identifies a kinase inhibitor as a candidate therapeutic for ALS. Cell Stem Cell 12, 713–726 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  176. 176.

    Belzil, V. V. et al. Characterization of DNA hypermethylation in the cerebellum of c9FTD/ALS patients. Brain Res. 1584, 15–21 (2014).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  177. 177.

    Xi, Z. et al. The C9orf72 repeat expansion itself is methylated in ALS and FTLD patients. Acta Neuropathol. 129, 715–727 (2015).

    PubMed  Article  CAS  Google Scholar 

  178. 178.

    Esanov, R. et al. A C9ORF72 BAC mouse model recapitulates key epigenetic perturbations of ALS/FTD. Mol. Neurodegener. 12, 46 (2017).

    PubMed  PubMed Central  Article  Google Scholar 

  179. 179.

    Zeier, Z. et al. Bromodomain inhibitors regulate the C9ORF72 locus in ALS. Exp. Neurol. 271, 241–250 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  180. 180.

    Bauer, P. O. Methylation of C9orf72 expansion reduces RNA foci formation and dipeptide-repeat proteins expression in cells. Neurosci. Lett. 612, 204–209 (2016).

    PubMed  Article  CAS  Google Scholar 

  181. 181.

    McMillan, C. T. et al. C9orf72 promoter hypermethylation is neuroprotective: neuroimaging and neuropathologic evidence. Neurology 84, 1622–1630 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  182. 182.

    Russ, J. et al. Hypermethylation of repeat expanded C9orf72 is a clinical and molecular disease modifier. Acta Neuropathol. 129, 39–52 (2015).

    PubMed  Article  CAS  Google Scholar 

  183. 183.

    Lee, Y. B. et al. Hexanucleotide repeats in ALS/FTD form length-dependent RNA foci, sequester RNA binding proteins, and are neurotoxic. Cell Rep. 5, 1178–1186 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  184. 184.

    Cooper-Knock, J. et al. Sequestration of multiple RNA recognition motif-containing proteins by C9orf72 repeat expansions. Brain 137, 2040–2051 (2014).

    PubMed  PubMed Central  Article  Google Scholar 

  185. 185.

    Cooper-Knock, J. et al. Antisense RNA foci in the motor neurons of C9ORF72-ALS patients are associated with TDP-43 proteinopathy. Acta Neuropathol. 130, 63–75 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  186. 186.

    Davidson, Y. S. et al. Heterogeneous ribonuclear protein A3 (hnRNP A3) is present in dipeptide repeat protein containing inclusions in frontotemporal lobar degeneration and motor neurone disease associated with expansions in C9orf72 gene. Acta Neuropathol. Commun. 5, 31 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  187. 187.

    Conlon, E. G. et al. The C9ORF72 GGGGCC expansion forms RNA G-quadruplex inclusions and sequesters hnRNP H to disrupt splicing in ALS brains. eLife 5, e17820 (2016).

    PubMed  PubMed Central  Article  Google Scholar 

  188. 188.

    Stopford, M. J. et al. C9ORF72 hexanucleotide repeat exerts toxicity in a stable, inducible motor neuronal cell model, which is rescued by partial depletion of Pten. Hum. Mol. Genet. 26, 1133–1145 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  189. 189.

    Mori, K. et al. hnRNP A3 binds to GGGGCC repeats and is a constituent of p62-positive/TDP-43-negative inclusions in the hippocampus of patients with C9orf72 mutations. Acta Neuropathol. 125, 413–423 (2013).

    PubMed  Article  CAS  Google Scholar 

  190. 190.

    Haas, S. et al. A 39-kD DNA-binding protein from mouse brain stimulates transcription of myelin basic protein gene in oligodendrocytic cells. J. Cell Biol. 130, 1171–1179 (1995).

    PubMed  Article  CAS  Google Scholar 

  191. 191.

    Gallia, G. L., Johnson, E. M. & Khalili, K. Puralpha: a multifunctional single-stranded DNA- and RNA-binding protein. Nucleic Acids Res. 28, 3197–3205 (2000).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  192. 192.

    Ohashi, S. et al. The single-stranded DNA- and RNA-binding proteins pur alpha and pur beta link BC1 RNA to microtubules through binding to the dendrite-targeting RNA motifs. J. Neurochem. 75, 1781–1790 (2000).

    PubMed  Article  CAS  Google Scholar 

  193. 193.

    Kanai, Y., Dohmae, N. & Hirokawa, N. Kinesin transports RNA: isolation and characterization of an RNA-transporting granule. Neuron 43, 513–525 (2004).

    PubMed  Article  CAS  Google Scholar 

  194. 194.

    Daigle, J. G. et al. Pur-alpha regulates cytoplasmic stress granule dynamics and ameliorates FUS toxicity. Acta Neuropathol. 131, 605–620 (2016).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  195. 195.

    Celona, B. et al. Suppression of C9orf72 RNA repeat-induced neurotoxicity by the ALS-associated RNA-binding protein Zfp106. eLife 6, e19032 (2017).

    PubMed  PubMed Central  Article  Google Scholar 

  196. 196.

    Prudencio, M. et al. Distinct brain transcriptome profiles in C9orf72-associated and sporadic ALS. Nat. Neurosci. 18, 1175–1182 (2015).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  197. 197.

    Panda, S. K. et al. Highly efficient targeted mutagenesis in mice using TALENs. Genetics 195, 703–713 (2013).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  198. 198.

    Herranz-Martin, S. et al. Viral delivery of C9orf72 hexanucleotide repeat expansions in mice leads to repeat-length-dependent neuropathology and behavioural deficits. Dis. Model. Mech. 10, 859–868 (2017).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

Download references

Acknowledgements

R.B. is a Leonard Wolfson Clinical Research Training Fellow and is funded by a Wellcome Trust Research Training Fellowship (107196/Z/14/Z). A.M.I. is funded by the Motor Neuron Disease Association, Alzheimer’s Research UK, the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (648716 — C9ND) and the UK Dementia Research Institute. The authors thank S. Mizielinska for reviewing the manuscript and assistance with figures and M. Guadalupi and R. Saccon for assistance with and design of figures.

Reviewer information

Nature Reviews Neurology thanks P. Shaw and the other anonymous reviewers for their contribution to the peer review of this work.

Author information

Affiliations

Authors

Contributions

Both authors researched data for the article, discussed the content, wrote the article and reviewed and edited the manuscript before submission.

Corresponding author

Correspondence to Adrian M. Isaacs.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Glossary

Repeat-associated non-ATG (RAN) translation

Translation is canonically dependent on an ATG start codon for initiation. RAN translation is a non-canonical form of translation that, in the presence of repetitive sequences, can start without the need for an ATG codon.

Hairpins

Secondary structures in which an RNA or DNA molecule folds back onto itself to resemble a hairpin.

G-quadruplexes

Secondary structures formed by guanine-rich RNA or DNA molecules consisting of a stack of G-quartets (four guanine residues aligned in a square planar configuration).

i-motifs

Four-stranded secondary structures formed by cytosine-rich DNA or RNA molecules.

Frontotemporal lobar degeneration

(FTLD). A term describing the pathological findings observed in patients with frontotemporal dementia (FTD); however, FTLD and FTD are also often used interchangeably to describe the clinical syndrome.

Cryo-electron tomography

A high-resolution technique that involves collecting a series of tilted images of frozen hydrated samples using an electron microscope to produce a 3D reconstruction of the sample.

Bacterial artificial chromosome

(BAC). A vector for maintaining large pieces of DNA, often 50–200 kb in size.

P-bodies

Processing bodies, or P-bodies, are membrane-less organelles within the cytoplasm that are involved in translational repression of mRNAs and in mRNA silencing and degradation.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Balendra, R., Isaacs, A.M. C9orf72-mediated ALS and FTD: multiple pathways to disease. Nat Rev Neurol 14, 544–558 (2018). https://doi.org/10.1038/s41582-018-0047-2

Download citation

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing