Targeted degradation of sense and antisense C9orf72 RNA foci as therapy for ALS and frontotemporal degeneration

Proc Natl Acad Sci U S A. 2013 Nov 19;110(47):E4530-9. doi: 10.1073/pnas.1318835110. Epub 2013 Oct 29.

Abstract

Expanded hexanucleotide repeats in the chromosome 9 open reading frame 72 (C9orf72) gene are the most common genetic cause of ALS and frontotemporal degeneration (FTD). Here, we identify nuclear RNA foci containing the hexanucleotide expansion (GGGGCC) in patient cells, including white blood cells, fibroblasts, glia, and multiple neuronal cell types (spinal motor, cortical, hippocampal, and cerebellar neurons). RNA foci are not present in sporadic ALS, familial ALS/FTD caused by other mutations (SOD1, TDP-43, or tau), Parkinson disease, or nonneurological controls. Antisense oligonucleotides (ASOs) are identified that reduce GGGGCC-containing nuclear foci without altering overall C9orf72 RNA levels. By contrast, siRNAs fail to reduce nuclear RNA foci despite marked reduction in overall C9orf72 RNAs. Sustained ASO-mediated lowering of C9orf72 RNAs throughout the CNS of mice is demonstrated to be well tolerated, producing no behavioral or pathological features characteristic of ALS/FTD and only limited RNA expression alterations. Genome-wide RNA profiling identifies an RNA signature in fibroblasts from patients with C9orf72 expansion. ASOs targeting sense strand repeat-containing RNAs do not correct this signature, a failure that may be explained, at least in part, by discovery of abundant RNA foci with C9orf72 repeats transcribed in the antisense (GGCCCC) direction, which are not affected by sense strand-targeting ASOs. Taken together, these findings support a therapeutic approach by ASO administration to reduce hexanucleotide repeat-containing RNAs and raise the potential importance of targeting expanded RNAs transcribed in both directions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyotrophic Lateral Sclerosis / drug therapy*
  • Amyotrophic Lateral Sclerosis / genetics
  • Animals
  • Blotting, Southern
  • C9orf72 Protein
  • Central Nervous System / cytology
  • Central Nervous System / metabolism
  • DNA Primers / genetics
  • DNA Repeat Expansion / genetics*
  • Fibroblasts / metabolism
  • Frontotemporal Lobar Degeneration / drug therapy*
  • Frontotemporal Lobar Degeneration / genetics
  • Genetic Therapy / methods*
  • Genotype
  • In Situ Hybridization, Fluorescence
  • Mice
  • Oligonucleotides, Antisense / administration & dosage
  • Oligonucleotides, Antisense / genetics
  • Oligonucleotides, Antisense / pharmacology*
  • Oligonucleotides, Antisense / therapeutic use
  • Proteins / genetics*
  • Real-Time Polymerase Chain Reaction
  • Sequence Analysis, RNA

Substances

  • C9orf72 Protein
  • C9orf72 protein, human
  • DNA Primers
  • Oligonucleotides, Antisense
  • Proteins