Expanded GGGGCC repeat RNA associated with amyotrophic lateral sclerosis and frontotemporal dementia causes neurodegeneration

Proc Natl Acad Sci U S A. 2013 May 7;110(19):7778-83. doi: 10.1073/pnas.1219643110. Epub 2013 Apr 3.


Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) share phenotypic and pathologic overlap. Recently, an expansion of GGGGCC repeats in the first intron of C9orf72 was found to be a common cause of both illnesses; however, the molecular pathogenesis of this expanded repeat is unknown. Here we developed both Drosophila and mammalian models of this expanded hexanucleotide repeat and showed that expression of the expanded GGGGCC repeat RNA (rGGGGCC) is sufficient to cause neurodegeneration. We further identified Pur α as the RNA-binding protein of rGGGGCC repeats and discovered that Pur α and rGGGGCC repeats interact in vitro and in vivo in a sequence-specific fashion that is conserved between mammals and Drosophila. Furthermore, overexpression of Pur α in mouse neuronal cells and Drosophila mitigates rGGGGCC repeat-mediated neurodegeneration, and Pur α forms inclusions in the fly eye expressing expanded rGGGGCC repeats, as well as in cerebellum of human carriers of expanded GGGGCC repeats. These data suggest that expanded rGGGGCC repeats could sequester specific RNA-binding protein from their normal functions, ultimately leading to cell death. Taken together, these findings suggest that the expanded rGGGGCC repeats could cause neurodegeneration, and that Pur α may play a role in the pathogenesis of amyotrophic lateral sclerosis and frontotemporal dementia.

Keywords: RNA-mediated neurodegeneration; fly model.

Publication types

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

MeSH terms

  • Amyotrophic Lateral Sclerosis / genetics*
  • Animals
  • Binding Sites
  • Brain / pathology
  • DNA Repeat Expansion*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster
  • Exons
  • Frontotemporal Dementia / genetics*
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Introns
  • Mice
  • Motor Neurons / pathology
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Neurons / metabolism
  • Oligonucleotides / genetics
  • Open Reading Frames
  • Plasmids / metabolism
  • RNA / genetics
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism


  • DNA-Binding Proteins
  • Drosophila Proteins
  • Nerve Tissue Proteins
  • Oligonucleotides
  • PURA protein, human
  • Pur-alpha protein, Drosophila
  • Pura protein, mouse
  • RNA-Binding Proteins
  • Transcription Factors
  • Green Fluorescent Proteins
  • RNA