However, knockdown of Dicer, Argonaute 1 (Ago1) and Argonaute 2 (Ago2), which play a key role in RNAi, did not prevent FMR1 gene silencing in FXS-hESC derived-neurons, ruling out the involvement of RNAi in silencing FM alleles [15]. The gene discussed is FMR1; the disease is fragile X syndrome.