BRAIN CAPILLARY ENDOTHELIAL-CELLS EXPRESS MBEC1, A PROTEIN THAT IS RELATED TO THE CLOSTRIDIUM-PERFRINGENS ENTEROTOXIN RECEPTORS

Brain capillary endothelial cells compose the blood-brain barrier, whi ch has a crucial role in maintaining the normal extracellular environm ent of the central nervous system. We have developed a method to isola te endothelial cells from mouse brain and maintain them in a relativel y pure primary culture. Using a subtractive hybridization technique, a novel cDNA, termed MBEC1 (mouse brain endothelial cell 1), has been i solated from the cultured mouse brain capillary endothelial cells. MBE C1 is a 1435-bp cDNA predicted to encode a protein of 218 amino acids. The predicted protein is similar to those of the newly characterized Clostridium perfringens enterotoxin receptors and is the mouse homolog of a recently described human cDNA clone, which is hemizygously delet ed in individuals with velo-cardio-facial syndrome and DiGeorge syndro me. MBEC1 was expressed in our cultured MBEC, in freshly isolated MBEC , in a variety of mouse organs, and in mouse embryos as early as embry onic Day 7. In situ hybridization and immunocytochemical analyses reve aled the presence of the MBEC1 mRNA and its protein product in brain c apillary endothelial cells, as well as in a subset of other endothelia l and epithelial cells. Moreover, developmental regulation of expressi on of MBEC1 was present in respiratory epithelium. Our research thus p rovides a new molecule for further study of the function of normal and abnormal blood-brain barrier as well as of other specialized endothel ia and epithelia.