MOUSE MULTIDRUG-RESISTANCE 1A 3 GENE IS THE EARLIEST KNOWN ENDOTHELIAL-CELL DIFFERENTIATION MARKER DURING BLOOD-BRAIN-BARRIER DEVELOPMENT/

Molecular mechanisms of endothelial cell differentiation during blood- brain barrier (BBB) development is not well understood due to the lack of specific molecular markers. Here we describe that expression of th e mouse multidrug resistance 1a/3 (mdr1 alpha/3) gene can be detected specifically in subsets of vascular endothelial cells associated with neural tissues at as early as embryonic day 10.5 (E10.5). This onset o f mdr1 alpha/3 gene expression coincides with the previously described first appearance of morphologically distinct endothelial cells in neu ral tissues during BBB development. To our knowledge, the mdr1 alpha/3 gene is the earliest endothelial cell differentiation marker gene dur ing BBB development described thus far. In addition, we have found tha t neither the level nor pattern of mdr1 alpha/3 gene expression in BBB endothelial cells is affected by aberrant cortical neuronal layers in mutant mouse reeler. (C) 1995 Wiley-Liss, Inc.