β1 integrins in radial glia but not in migrating neurons are essential for the formation of cell layers in the cerebral cortex

Radial glial cells in the cerebral cortex serve as progenitors for neurons and glia and guide the migration of cortical neurons. The integrin α3β1 is thought to mediate interactions of migrating neurons with radial glial cells and to function as a receptor for the reelin signaling molecule. Here, we challenge this view and demonstrate that β1 integrins in migrating neurons are not essential for the formation of cell layers in the cerebral cortex. Cortical cell layers also form normally in mice deficient in the integrin α3β1. However, we provide evidence that β1 integrins in radial glia control the morphological differentiation of both glia and neurons. We conclude that β1 integrins in radial glia are required for the proper development of the cerebral cortex, whereas β1 integrins in migrating neurons are not essential for glial-guided migration and reelin signaling.