Differential expression of endothelial beta-catenin and plakoglobin duringdevelopment and maturation of the blood-brain and blood-retina barrier in the chicken

The development of the blood-brain barrier depends upon the formation of a closely regulated system of adherens and tight junctions. A prerequisite fo r a functional junction system is the linkage of transmembrane adhesion rec eptors (cadherins) to the cytoskeleton via catenins, The localization of sp ecific catenins at the adherens junction correlates with the stability of i nterendothelial contacts in vitro, but in vivo data are lacking thus far. I nvestigating brain angiogenesis in the chicken, we demonstrated that beta-c atenin, but not plakoglobin, initially codistributed with N-cadherin at the ablumenal endothelial membrane at contact sites to perivascular cells, fro m where both antigens disappeared during blood-brain barrier maturation. In contrast, plakoglobin was most prominent at the interendothelial junction where only small amounts of beta-catenin were present. Western-blot analysi s revealed a stronger developmental decrease of beta-catenin than plakoglob in, whereas N-cadherin was completely lost. beta-Catenin but not N-cadherin was reinduced in brain endothelial cells during dedifferentiation in vitro and localized to the interendothelial junctions. These first in vivo data support the hypothesis that endothelial beta-catenin and N-cadherin are tra nsiently relevant for the contact of brain endothelial to perivascular cell s. Plakoglobin seems not to interact with N-cadherin but is exclusively loc alized at interendothelial junctions providing evidence for its role in the formation of stable adherens junctions, which may play a role for the init iation, and/or stabilization of tight junctions. (C) 2000 Wiley-Liss, Inc.