Formation of the blood-brain barrier: Wnt signaling seals the deal

Capillaries in the brain are especially selective in determining which blood-borne components gain access to neurons. The structural elements of this blood–brain barrier (BBB) reside at the tight junction, an intercellular protein complex that welds together adjacent endothelial cell membranes in the microvasculature. In this issue, Liebner et al. (Liebner, S., M. Corada, T. Bangsow, J. Babbage, A. Taddei, C.J. Czupalla, M. Reis, A. Felici, H. Wolburg, M. Fruttiger, et al. 2008. J. Cell Biol. 183: 409–417) report that Wnt signaling plays an active role in the development of the BBB by regulating expression of key protein constituents of the tight junction. Such mechanistic insight has implications for a variety of neuropathological states in which the BBB is breached.