Acta Neuropathologica

, Volume 128, Issue 4, pp 525–541

C9orf72 hypermethylation protects against repeat expansion-associated pathology in ALS/FTD

  • Elaine Y. Liu
  • Jenny Russ
  • Kathryn Wu
  • Donald Neal
  • Eunran Suh
  • Anna G. McNally
  • David J. Irwin
  • Vivianna M. Van Deerlin
  • Edward B. Lee
Original Paper

DOI: 10.1007/s00401-014-1286-y

Cite this article as:
Liu, E.Y., Russ, J., Wu, K. et al. Acta Neuropathol (2014) 128: 525. doi:10.1007/s00401-014-1286-y

Abstract

Hexanucleotide repeat expansions of C9orf72 are the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal degeneration. The mutation is associated with reduced C9orf72 expression and the accumulation of potentially toxic RNA and protein aggregates. CpG methylation is known to protect the genome against unstable DNA elements and to stably silence inappropriate gene expression. Using bisulfite cloning and restriction enzyme-based methylation assays on DNA from human brain and peripheral blood, we observed CpG hypermethylation involving the C9orf72 promoter in cis to the repeat expansion mutation in approximately one-third of C9orf72 repeat expansion mutation carriers. Promoter hypermethylation of mutant C9orf72 was associated with transcriptional silencing of C9orf72 in patient-derived lymphoblast cell lines, resulting in reduced accumulation of intronic C9orf72 RNA and reduced numbers of RNA foci. Furthermore, demethylation of mutant C9orf72 with 5-aza-deoxycytidine resulted in increased vulnerability of mutant cells to oxidative and autophagic stress. Promoter hypermethylation of repeat expansion carriers was also associated with reduced accumulation of RNA foci and dipeptide repeat protein aggregates in human brains. These results indicate that C9orf72 promoter hypermethylation prevents downstream molecular aberrations associated with the hexanucleotide repeat expansion, suggesting that epigenetic silencing of the mutant C9orf72 allele may represent a protective counter-regulatory response to hexanucleotide repeat expansion.

Keywords

NeurodegenerationAmyotrophic lateral sclerosisDementiaMotor neuron diseaseFrontotemporal lobar degenerationEpigenetics

Supplementary material

401_2014_1286_MOESM1_ESM.pdf (399 kb)
Supplementary material 1 (PDF 399 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Elaine Y. Liu
    • 1
    • 2
  • Jenny Russ
    • 1
    • 2
  • Kathryn Wu
    • 1
    • 2
  • Donald Neal
    • 2
  • Eunran Suh
    • 2
  • Anna G. McNally
    • 1
    • 2
  • David J. Irwin
    • 2
    • 3
  • Vivianna M. Van Deerlin
    • 2
  • Edward B. Lee
    • 1
    • 2
  1. 1.Translational Neuropathology Research LaboratoryPerelman School of Medicine at the University of PennsylvaniaPhiladelphiaUSA
  2. 2.Department of Pathology and Laboratory MedicinePerelman School of Medicine at the University of PennsylvaniaPhiladelphiaUSA
  3. 3.Department of NeurologyPerelman School of Medicine at the University of PennsylvaniaPhiladelphiaUSA