The tumor suppressor protein PTEN is a member of the protein tyrosine phosphatase family that can negatively regulate the serine/threonine kinase Akt to exert its tumor suppressor function.26 The protein phosphatase activity of PTEN can regulate cell migration, spreading and growth.27 PTEN is widely expressed in the mouse CNS and preferentially in neurons such as large pyramidal neurons.28 PTEN localizes to both the nucleus and cytoplasm of neuronal and glial cells.28, 29, 30 Significant progress has been made in investigating the broader role of PTEN in the brain. This evidence concerns the gene MARK2 and neoplasm.