A Need for Glia

Abstract

DEVELOPMENT The mammalian cerebral cortex, the seat of higher thought, develops from the inside out, as younger neurons born in the ventricular zone migrate past older neurons to form ever more superficial layers. Radial glial cells serve as guide wires along which the migrating neurons travel, and these same radial glial cells also serve to produce new neurons. As migrating neurons navigate through the glial cell scaffold, they move stepwise by means of transient adhesive contacts mediated by gap junction proteins. Integrins are αβ subunit receptors located in the plasma membrane and link the extracellular matrix to the intracellular cytoskeleton. Belvindrah et al. have taken a closer look at how β1 integrin contributes to the organization of these cortical cell migrations. They used an existing mouse line, in which both radial glia and migrating neurons were deficient in β1 integrin, and compared it with a mouse line they developed for this analysis, with β1 integrin knocked out only in the migrating neurons. When the radial glia lacked β1 integrin, they seemed disorganized in their anchor points, and the cortex developed abnormally, whereas when only the neurons lacked β1 integrin, migration proceeded normally. Tissue culture analysis showed that the normal formation of neurite extensions depended on the expression of β1 integrin in the glia, but not in the neurons. It seems that what matters for how β1 integrin affects the layering of the developing cortex is not its expression in neurons but rather its expression in glial cells. — PJH J. Neurosci. 27 , 13854 (2007).