β1 integrins control the formation of cell chains in the adult rostral migratory stream

The subventricular zone ( SVZ) of the lateral ventricle is the major site of neurogenesis in the adult brain. Neuroblasts that are born in the SVZ migrate as chains along the rostral migratory stream ( RMS) to the olfactory bulb. Little is known about the mechanisms that control interactions between neuroblasts during their migration. Here we show that migrating neuroblasts express beta 1integrins and that the integrin ligand laminin is localized to cell chains. Using genetically modified mice and time- lapse video recordings of SVZ explants, we demonstrate that beta 1 integrins and laminin promote the formation of cell chains. Laminin also induces the aggregation of purified neuroblasts. We conclude that the formation of cell chains in the RMS is controlled in part by beta 1 integrins via binding to laminin. In addition, we provide evidence that beta 1 class integrins are required for the maintenance of the glial tubes and that defects in the glial tubes lead to the ectopic migration of neuroblasts into the surrounding tissue.