C9orf72 and amyotrophic lateral sclerosis: The 2020 study identified the CSF presence of the AQEEAEAEER or AQEE-10 (proVGF586-595) by analyzing samples from ALS and frontotemporal dementia (FTD) patients, both with hexanucleotide repeat expansion in the C9orf72 gene, which is the most common mutation associated with ALS (C9-ALS) and frontotemporal dementia (C9-FTD).