title: The Gs-linked receptor GPR3 inhibits the proliferation of cerebellar granule cells during postnatal development.
abstract: BACKGROUND
  During postnatal murine and rodent cerebellar development, cerebellar granule precursors (CGP) gradually stop proliferating as they differentiate after migration to the internal granule layer (IGL). Molecular events that govern this program remain to be fully elucidated. GPR3 belongs to a family of Gs-linked receptors that activate cyclic AMP and are abundantly expressed in the adult brain.
  
  
  RESULTS
  To investigate the role of this orphan receptor in CGP differentiation, we determined that exogenous GPR3 expression in rat cerebellar granule neurons partially antagonized the proliferative effect of Sonic hedgehog (Shh), while endogenous GPR3 inhibition by siRNA stimulated Shh-induced CGP proliferation. In addition, exogenous GPR3 expression in CGPs correlated with increased p27/kip expression, while GPR3 knock-down led to a decrease in p27/kip expression. In wild-type mice, GPR3 expression increased postnatally and its expression was concentrated in the internal granular layer (IGL). In GPR3 -/- mice, the IGL was widened with increased proliferation of CGPs, as measured by bromodeoxyuridine incorporation. Cell cycle kinetics of GPR3-transfected medulloblastoma cells revealed a G0/G1 block, consistent with cell cycle exit.
  
  
  CONCLUSIONS
  These results thus indicate that GPR3 is a novel antiproliferative mediator of CGPs in the postnatal development of murine cerebellum.
authors.affiliation: Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery, The Ohio State University, Columbus, OH, USA.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tanaka
authors.forename: Imran Mohammed
authors.initials: IM
authors.lastname: Shaikh
authors.forename: E Antonio
authors.initials: EA
authors.lastname: Chiocca
authors.forename: Yoshinaga
authors.initials: Y
authors.lastname: Saeki
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D049109:Cell Proliferation; D002531:Cerebellum / Q000166:cytology*; D000242:Cyclic AMP / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis* / Q000502:physiology*
chemical_list: C494613:GPR3 protein, mouse; D053823:Hedgehog Proteins; D043562:Receptors, G-Protein-Coupled; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000242:Cyclic AMP