FMR1 and fragile X syndrome: The Fmr1 gene is thought to be bound and therefore regulated by CREB (Kanellopoulos et al., 2012; Rani and Prasad, 2015), however the relationship of CREB signaling to FXS synaptic plasticity requires further investigation, especially considering the role that FMRP has in the modulation of cAMP and cGMP levels, two molecules upstream the CREB expression (Delhaye and Bardoni, 2021).