A Novel Gene Family May Encode Endothelial Cell Specific Adhesion-Like Molecules: An Extracellular Loop-Repeat-Loop (LRL) Motif and Cytoplasmic Tyrosine Kinase Domains

Vascular endothelium separates underlying tissues from the blood circulation. Because of this organization, endothelial cells play pivotal roles for signaling between the blood circulation and tissues. The signaling functions of vascular endothelial cells in the central nervous system (CNS) are especially important because of the existence of the blood-brain barrier (BBB) against diffusion-mediated signal transmission between the CNS and the blood circulation. This indicates that any signals have to be integrated into the endothelial signal transduction machinery before they reach either side of the endothelium. The vascular system in the CNS has another unique organization. It is surrounded by a complex and heterologous cellular organization as opposed to the relatively simple and homogeneous tissue organization in peripheral tissues. The developmental program of the endothelium in the CNS may be more complex than in peripheral tissues because development and differentiation of endothelial cells in the CNS may be affected by heterologous cellular interactions.