FMR1 and fragile X syndrome: FMRP drives cAMP induction and PKA activation in Fragile X syndrome (FXS) mouse/Drosophila disease models and human FXS patient cell cultures lacking FMRP (Berry-Kravis et al., 1995; Kelley et al., 2007; Sears and Broadie, 2020), and FMRP loss-of-function (LOF) impairs both learning and memory (Bolduc et al., 2008).