Analyzing the Endothelial Cell-Expressed Prion Gene Prnd in Vascular Development

Abstract The central nervous system (CNS), comprised of the brain, spinal cord and retina, is the most vascularized organ system in the human body. Neurons and glial cells closely contact blood vessels and communicate with vascular endothelial cells and pericytes to control normal CNS development and physiology. Blood vessel dysfunction occurs in multiple CNS diseases, including developmental brain disorders, retinal deficits, and age-related neurodegeneration. We understand surprisingly little about mechanisms that regulate normal CNS vascular development and physiology or how these events go awry during disease pathogenesis. To characterize new and potentially targetable factors that control blood vessel morphogenesis in the developing CNS, we queried open-source databases to identify genes with putative roles in vascular endothelial cell growth, differentiation and sprouting. These efforts have led to the current project focused on Prnd, a member of the prion gene family that is expressed in the CNS vascular endothelium. We present a substantial amount of data that bolster our working hypothesis that glycophosphatidylinositol (GPI)-linked Prnd activates endothelial cell signaling pathways to regulate angiogenesis and blood vessel permeability in the brain and retina. Furthermore, we propose that abnormal Prnd expression and function contributes to brain and retinal blood vessel pathologies. To test our hypotheses, we will (1) utilize biochemical strategies and high-resolution cell imaging methods to analyze Prnd-dependent signaling pathways that promote endothelial cell differentiation, growth and migration; (2) analyze roles for Prnd in developmental and pathological CNS angiogenesis; and (3) identify and characterize cues in the CNS microenvironment that promote Prnd expression and functions in angiogenic endothelial cells. In summary, these experiments will reveal novel functions for Prnd in regulating CNS blood vessel morphogenesis and may identify new targets for therapeutically inhibiting pathological angiogenesis in the CNS.