In particular, it is mainly localized in the cortex, hippocampus and striatum [22, 39, 40] suggesting that PDE2A may regulate neuronal cAMP and cGMP levels in brain areas involved in emotions, perception, learning, and memory [41], brain functions often disrupted in patients affected by FXS or other forms of ASD [42]. This evidence concerns the gene PDE2A and fragile X syndrome.