Inactivating mutation in Tsc2 (Tsc2+/− mice) showed defects in axon guidance [11] and cognitive deficits such as impaired water maze performance [12], and mice with Fmr1-knockout (KO) presented impairments in long-term depression, hyperactivity, anxiety-like, and unusual social behaviors [13]. Here, TSC2 is linked to major depressive disorder.