PAK1 and fragile X syndrome: In contrast to these reports, the higher PAK1 S199/S204 phosphorylations are relevant to the seizure susceptibility in fragile X mental retardation 1 (Fmr1) KO mice (a Fragile X syndrome model), since FRAX486 (a PAKs inhibitor) reduces audiogenic seizure activity in this model [63, 64].