title: Hedgehog and PI-3 kinase signaling converge on Nmyc1 to promote cell cycle progression in cerebellar neuronal precursors.
abstract: Neuronal precursor cells in the developing cerebellum require activity of the sonic hedgehog (Shh) and phosphoinositide-3-kinase (PI3K) pathways for growth and survival. Synergy between the Shh and PI3K signaling pathways are implicated in the cerebellar tumor medulloblastoma. Here, we describe a mechanism through which these disparate signaling pathways cooperate to promote proliferation of cerebellar granule neuron precursors. Shh signaling drives expression of mRNA encoding the Nmyc1 oncoprotein (previously N-myc), which is essential for expansion of cerebellar granule neuron precursors. The PI3K pathway stabilizes Nmyc1 protein via inhibition of GSK3-dependent Nmyc1 phosphorylation and degradation. The effects of PI3K activity on Nmyc1 stabilization are mimicked by insulin-like growth factor, a PI3K agonist with roles in central nervous system precursor growth and tumorigenesis. These findings indicate that Shh and PI3K signaling pathways converge on N-Myc to regulate neuronal precursor cell cycle progression. Furthermore, they provide a rationale for therapeutic targeting of PI3K signaling in medulloblastoma.
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Kenney
authors.forename: Hans R
authors.initials: HR
authors.lastname: Widlund
authors.forename: David H
authors.initials: DH
authors.lastname: Rowitch
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002453:Cell Cycle / Q000502:physiology*; D002454:Cell Differentiation; D002531:Cerebellum / Q000166:cytology / Q000502:physiology*; D053823:Hedgehog Proteins; D051379:Mice; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D015534:Trans-Activators; D019869:Phosphatidylinositol 3-Kinases