Patterns of laminins and integrins in the embryonic ventricular zone of the CNS.

The extracellular matrix (ECM) provides both a physical framework and a microenvironment that supplies instructive signals from the earliest stages of multicellular development. As a first step toward understanding the role of the ECM in regulating the behavior of neural stem cells (NSCs), here we show the localization of laminins, a heterotrimeric family of ECM molecules expressed in many different stem cell microenvironments, and their corresponding receptors in the embryonic murine ventricular zone (VZ) within which the NSCs undergo symmetrical and asymmetrical divisions required for cortical development. In addition to the presence of laminins containing both the alpha2 and alpha4 chains, we find distinct patterns of ECM receptor expression in the VZ and in the overlying cortex. Neural stem cells derived from the VZ express high levels of the integrin laminin receptor alpha6beta1. At developmental stages at which NSCs undergo asymmetrical divisions, integrin beta1 was unevenly distributed in some mitotic pairs at the ventricular wall. These results suggest a significant role in the regulation of NSC fate for laminin/integrin signaling within the microenvironment of the VZ and provide a framework for future molecular and cellular analyses of the role of the ECM in neural development.