APP and fragile X syndrome: In addition to those described here, other therapeutic targets for future treatment of FXS can be considered, for example, Amyloid Precursor Protein (APP), Brain-Derived Neurotrophic Factor (BDNF), cAMP and N-methyl-D-aspartate (NMDA) receptor as illustrated in several recent reviews (Wei et al., 2012; Castrén and Castrén, 2014; Androschuk et al., 2015; Tian et al., 2015; Westmark et al., 2016).