BMPing Up Angiogenesis via BMPER

Over the past 20 years, there has been considerable interest in the elucidation of factors that mediate angiogenesis. Early efforts, including Michaelson's description of “Factor X” in mediating retinal neovascularization and Folkman's attempts at isolating “tumor angiogenesis factor,” have blossomed into a plethora of investigations identifying regulators, both positive and negative, of blood vessel formation.1,2 These efforts led to the identification of factors such as vascular endothelial growth factor, acid- and basic-fibroblast growth factor, angiogenin, and angiopoietins, to name a few.3–5 Subsequent detailed investigations have revealed that finely tuned and precisely coordinated expression of these factors is critical for angiogenesis during both development and adult life. Failure to coordinate expression has significant implications, as excess angiogenesis can contribute to tumor growth and inflammatory disorders, whereas insufficient angiogenesis can contribute to ischemic heart disease and preeclampsia.6See accompanying article on page 2216More recently, additional angiogenic mediators, including Notch, Wnt, and morphogens such as bone morphogenetic proteins (BMPs), have emerged as critical regulators for proper blood vessel formation. BMPs, members of the transforming growth factor-β superfamily of proteins, were initially characterized by their ability to …