CRBP-III:lacZ expression pattern reveals a novel heterogeneity of vascular endothelial cells.

Vascular endothelial cells are structurally and functionally heterogeneous. However, the molecular basis of this heterogeneity remains poorly defined. We used subtractive and differential screening to identify genes that exhibit heterogeneous expression patterns among vascular endothelial cells. One such gene is cellular retinol binding protein III (CRBP-III/Rbp7). Analysis of the lacZ knockin line for this gene (CRBP-III:lacZ) revealed a novel organ-specific vascular endothelial expression pattern. LacZ was expressed in vascular endothelial cells in heart, skeletal muscle, adipose tissues, thymus, and salivary gland. However, it was not detected in other tissues such as brain, liver, and lung. Furthermore, the expression within each organ was primarily restricted to small capillary endothelial cells, but could not be detected in larger vessels. This organ-specific vascular endothelial expression of CRPB:lacZ is relatively resistant to the changes of organ microenvironment. However, the level of expression can be modified by vitamin A deficiency. Therefore, our results provide novel molecular evidence for the heterogeneity of vascular endothelial cells.