MAPK3 and fragile X syndrome: Importantly, genetic reduction of Adcy1 normalized the elevated level of p-ERK1/2, pAkt and pS6K1 (at the ERK1/2 target site Thr421/Ser424 and the PI3K target site Thr389) (Fig. 2a–c) in DKO mice, suggesting that the loss of FMRP-dependent translation suppression of Adcy1 is a prevailing cause for aberrant neuronal signalling in FXS.