title: Temporal-specific roles of Rac1 during vascular development and retinal angiogenesis.
abstract: Angiogenesis, the formation of new blood vessels by remodeling and growth of pre-existing vessels, is a highly orchestrated process that requires a tight balance between pro-angiogenic and anti-angiogenic factors and the integration of their corresponding signaling networks. The family of Rho GTPases, including RhoA, Rac1, and Cdc42, play a central role in many cell biological processes that involve cytoskeletal changes and cell movement. Specifically for Rac1, we have shown that excision of Rac1 using a Tie2-Cre animal line results in embryonic lethality in midgestation (embryonic day (E) 9.5), with multiple vascular defects. However, Tie2-Cre can be also expressed during vasculogenesis, prior to angiogenesis, and is active in some hematopoietic precursors that can affect vessel formation. To circumvent these limitations, we have now conditionally deleted Rac1 in a temporally controlled and endothelial-restricted fashion using Cdh5(PAC)-iCreERT2 transgenic mice. In this highly controlled experimental in vivo system, we now show that Rac1 is required for embryonic vascular integrity and angiogenesis, and for the formation of superficial and deep vascular networks in the post-natal developing retina, the latter involving a novel specific function for Rac1 in vertical blood vessel sprouting. Aligned with these findings, we show that RAC1 is spatially involved in endothelial cell migration, invasion, and radial sprouting activities in 3D collagen matrix in vitro models. Hence, Rac1 and its downstream molecules may represent potential anti-angiogeneic therapeutic targets for the treatment of many human diseases that involve aberrant neovascularization and blood vessel overgrowth.
authors.affiliation: Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, United States.
authors.forename: Nijiro
authors.initials: N
authors.lastname: Nohata
authors.affiliation: Laboratory of Stem Cell and Neuro-Vascular Biology, Genetics and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, United States.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Section on Vertebrate Development, Program in the Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States.
authors.forename: Amber N
authors.initials: AN
authors.lastname: Stratman
authors.affiliation: Department of Tissue Morphogenesis, Max Planck Institute for Molecular Biomedicine and Faculty of Medicine, University of Münster, D-48149 Münster, Germany.
authors.forename: Ralf H
authors.initials: RH
authors.lastname: Adams
authors.affiliation: Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, University of Cincinnati College of Medicine, Cincinnati, OH 45229, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Section on Vertebrate Development, Program in the Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States.
authors.forename: Brant M
authors.initials: BM
authors.lastname: Weinstein
authors.affiliation: Laboratory of Stem Cell and Neuro-Vascular Biology, Genetics and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, United States.
authors.forename: Yoh-Suke
authors.initials: YS
authors.lastname: Mukouyama
authors.affiliation: Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, United States; Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, United States. Electronic address: sgutkind@ucsd.edu.
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
mesh_terms: D000483:Alleles; D000818:Animals; D002465:Cell Movement; D042783:Endothelial Cells / Q000166:cytology*; D004730:Endothelium, Vascular / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D005838:Genotype; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic; D009479:Neuropeptides / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D012160:Retina / Q000196:embryology*; D012171:Retinal Vessels / Q000196:embryology / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
chemical_list: D009479:Neuropeptides; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; C484602:Rac1 protein, mouse; D020830:rac1 GTP-Binding Protein
keywords: Angiogenesis; Conditional gene knockout mouse; In vitro three dimensional collagen matrix model; Rac1