Poly(GR) and poly(GA) in cerebrospinal fluid as potential biomarkers for C9ORF72-ALS/FTD

Nat Commun. 2022 May 19;13(1):2799. doi: 10.1038/s41467-022-30387-4.


GGGGCC repeat expansion in C9ORF72, which can be translated in both sense and antisense directions into five dipeptide repeat (DPR) proteins, including poly(GP), poly(GR), and poly(GA), is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we developed sensitive assays that can detect poly(GA) and poly(GR) in the cerebrospinal fluid (CSF) of patients with C9ORF72 mutations. CSF poly(GA) and poly(GR) levels did not correlate with age at disease onset, disease duration, or rate of decline of ALS Functional Rating Scale, and the average levels of these DPR proteins were similar in symptomatic and pre-symptomatic patients with C9ORF72 mutations. However, in a patient with C9ORF72-ALS who was treated with antisense oligonucleotide (ASO) targeting the aberrant C9ORF72 transcript, CSF poly(GA) and poly(GR) levels decreased approximately 50% within 6 weeks, indicating they may serve as sensitive fluid-based biomarkers in studies directed against the production of GGGGCC repeat RNAs or DPR proteins.

Trial registration: ClinicalTrials.gov NCT01925196.

Publication types

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

MeSH terms

  • Amyotrophic Lateral Sclerosis* / genetics
  • Amyotrophic Lateral Sclerosis* / metabolism
  • Biomarkers
  • C9orf72 Protein / genetics
  • C9orf72 Protein / metabolism
  • Dipeptides / metabolism
  • Frontotemporal Dementia* / genetics
  • Frontotemporal Dementia* / metabolism
  • Humans
  • Proteins


  • Biomarkers
  • C9orf72 Protein
  • C9orf72 protein, human
  • Dipeptides
  • Proteins
  • poly(glycyl-alanyl)

Associated data

  • ClinicalTrials.gov/NCT01925196