Skip to Content
MilliporeSigma
  • C9orf72 hypermethylation protects against repeat expansion-associated pathology in ALS/FTD.

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

Acta neuropathologica (2014-05-09)
Elaine Y Liu, Jenny Russ, Kathryn Wu, Donald Neal, Eunran Suh, Anna G McNally, David J Irwin, Vivianna M Van Deerlin, Edward B Lee
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Formamide, ReagentPlus®, ≥99.0% (GC)
Sigma-Aldrich
Formamide, spectrophotometric grade, ≥99%
Sigma-Aldrich
Formamide, BioUltra, for molecular biology, ≥99.5% (T)
Sigma-Aldrich
Formamide, ACS reagent, ≥99.5%
Sigma-Aldrich
Formamide, BioReagent, ≥99.5% (GC), for molecular biology
Sigma-Aldrich
Formamide, JIS special grade, ≥98.5%
Sigma-Aldrich
Formamide, SAJ first grade, ≥98.5%
Sigma-Aldrich
Isopropyl β-D-1-thiogalactopyranoside, ≥99% (TLC)
Sigma-Aldrich
IPTG, ≥99% (TLC), ≤0.1% Dioxane
Sigma-Aldrich
Maltose solution, for molecular biology, BioReagent, ~20% in H2O
Supelco
Formamide solution, NMR reference standard, 90% in DMSO-d6 (99.9 atom % D), NMR tube size 5 mm × 8 in.
Sigma-Aldrich
Formamide solution, NMR reference standard, 90% in DMSO-d6 (99.9 atom % D), NMR tube size 10 mm × 8 in.
Supelco
Formamide solution, NMR reference standard, 90% in DMSO-d6 (99.9 atom % D), NMR tube size 5 mm × 8 in.
Sigma-Aldrich
Isopropyl β-D-thiogalactopyranoside solution, ReadyMade IPTG solution for Blue-white screening
Sigma-Aldrich
DAPI, for nucleic acid staining
SAFC
Isopropyl β-D-1-thiogalactopyranoside