Atomic details of the G4 structure discovered in our work shed light on the structural diversity of G-quadruplexes adopted by d(G4C2) repeats and allow us to design small molecules to modulate aberrant transcription of C9orf72 gene related with ALS and FTD in particular by in silico drug screening studies. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.