Fig. 1. Tie2-Cre conditional v mutants do not develop cerebral vascular defects. (A-F) v integrin is not detected on cerebral endothelial cells or pericytes. Horizontal sections through the diencephalon of an E13.5 v^+/- embryo labeled with pre-absorbed anti-v antiserum (A,D), anti-PECAM (B), or anti-smooth muscle -actin (SMA) (E). v protein localizes to neuroepithelial processes (A,D). (C,F) Merged images: arrows indicate close juxtaposition between v-positive neuroepithelial processes with endothelial cells (C) and pericytes (F). Boxed areas are shown as higher magnification insets. (G) Generation of the conditional v mutant allele in endothelial cells. Tie2-Cre-mediated recombination deletes exon four, resulting in a conditional v-null allele (lower panel). Arrows indicate PCR primers for genotyping. (H) Cre-mediated recombination monitored by PCR using DNA isolated from PECAM/Flk1-positive brain endothelial cells (EC), or PECAM/Flk1-negative cells (C). In brain endothelial cells, there is a reduction in the intensity of the 350 bp band owing to recombination of the v-flox allele. We confirmed deletion of exon four using a primer pair that detects the deleted v-flox cassette (data not shown). (I-L) Brains dissected from P5 neonates. No grossly obvious cerebral vascular defects are present in control (I) or mutant (K). Hematoxylin and Eosin-stained coronal sections from control (J) and mutant (L) brains revealed no obvious microscopic neural or vascular defects.