Reelin binds α3β1 integrin and inhibits neuronal migration

Mice that are mutant for Reelin or Dab1, or doubly mutant for the VLDL receptor (VLDLR) and ApoE receptor 2 (ApoER2), show disorders of cerebral cortical lamination. How Reelin and its receptors regulate laminar organization of cerebral cortex is unknown. We show that Reelin inhibits migration of cortical neurons and enables detachment of neurons from radial glia. Recombinant and native Reelin associate with alpha 3 beta 1 integrin, which regulates neuron-glia interactions and is required to achieve proper laminar organization. The effect of Reelin on cortical neuronal migration in vitro and in vivo depends on interactions between Reelin and alpha 3 alpha 1 integrin. Absence of alpha 3 beta 1 leads to a reduction of Dab1, a signaling protein acting downstream of Reelin. Thus, Reelin may arrest neuronal migration and promote normal cortical lamination by binding alpha 3 beta 1 integrin and modulating integrin-mediated cellular adhesion.