To investigate this, Gendron et al. (2017) evaluated the effects of a ribonuclease H-active antisense oligonucleotide (ASO) that targets G4C2 repeat RNA on lymphoblastoid cell lines from C9orf72 ALS cases and in (G4C2)66 mice, and an ASO that targets intron 1 of C9orf72 on iPSC-derived neurons from C9orf72 ALS patients, and found that poly-GP levels were significantly decreased over time with treatment. Here, C9orf72 is linked to amyotrophic lateral sclerosis.