C9 and frontotemporal dementia: Together, these findings expand our knowledge of the structures of DNA GQs formed by long C9-HRE sequences, which may serve as therapeutic targets to prevent C9ALS/FTD, and also provide a natural small-molecule ligand that can efficaciously modulate C9-HRE GQs both in DNA and RNA levels, which may have potential implications for altering C9ALS/FTD disease pathogenesis.