Production of poly(GA) in C9ORF72 patient motor neurons derived from induced pluripotent stem cells

GGGGCC (G4C2) repeat expansion in the first intron of C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). A key pathological hallmark of C9ORF72-related ALS/FTD is the accumulation of dipeptide repeat (DPR) proteins synthesized from both sense and antisense repeat RNAs in affected neurons.To investigate how DPR proteins are synthesized in C9ORF72 human neurons, we used CRISPR-Cas9 technology to generate a homozygous deletion in the first intron of C9ORF72, 5′ to the G4C2 repeats to assess the effect of this deletion on DPR production.