NRP1 and NRP2 are mediators of neuronal guidance and angiogenesis. NRPs bind members of the class 3 Sema-phorin family, regulators of neuronal guidance, and members of the VEGF family of angiogenesis factors. Fujisawa and colleagues first identified NRP1 in 1991 as an adhesion molecule in developing nervous tissue; it was shown to be a 130- to 140-kDa highly conserved type 1 transmembrane glycoprotein. A second gene, NRP2, was identified in 1998 that had a 44 percent amino acid homology with NRP1.
A possible role of NRP1 in blood vessel development was first noted when NRP1 was overexpressed in mice. Besides ectopic sprouting and defasciculation of neurons, the mice also exhibited excess blood vessels. Subsequently, it was reported that NRP1 knockout mice exhibited various vascular abnormalities along with neuronal defects. The molecular connection of NRP1 to angiogenesis was noted when Klagsbrun and colleagues reported that VEGF, a major angiogenesis factor, was a ligand for NRP1 and NRP2.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.