Inactivating mutations of several negative regulators of the ERK and mTOR pathways, such as neurofibromin (neurofibromatosis type 1), harmartin, and tuberin (tuberous sclerosis), and PTEN (phosphatase and tensin homolog) are responsible for genetic disorders with a high prevalence of cognitive impairment and autism (Levitt and Campbell, 2009). Here, PTEN is linked to tuberous sclerosis.