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Principal Investigator: Xu Peng
Contact Information: Email: xp23@cornell.edu - Phone: 607-253-3884
Sponsor: American Heart Association-Northeast Affiliate
Grant Number: 0735543T
Title: Role & Mechanisms of Cdc42 in Vasculogenesis & Angiogenesis
Annual Direct Cost: $60,000
Project Period: 07/01/07-06/30/10
DESCRIPTION (provided by applicant): Cdc42 is a Ras-related GTPase that plays an important role in the regulation of actin cytoskeletal architecture. Blocking the ability of Cdc42 to activate its effectors has been shown to inhibit a range of cellular functions including cell polarization, migration and proliferation. Consistent with its critical roles in vitro, the total deletion of Cdc42 in mice resulted in embryonic lethality before E6.5. This early embryonic lethal phenotype of Cdc42-null mice has made it unusable to determine the role of Cdc42 in vascular development. To overcome this problem, we have generated Cdc42/flox mice with the Cdc42 gene flanked by two loxP sites. Crossing of the Cdc42/flox mice with vascular endothelial cells (ECs) specific Cre expression mice resulted in the inactivation of Cdc42 in ECs. Our preliminary results have demonstrated that the inactivation of Cdc42 in ECs resulted in embryonic lethality at E9.5 with brain and intersomitic angiogenesis defects, suggesting that Cdc42 plays an indispensable role in the development of the vascular system. In this proposal, we will investigate the role and mechanisms of Cdc42 in vasculogenesis and organ-specific angiogenesis in Cdc42 conditional knockout embryos. The TUNEL, Brdu incorporation and immunohistochemical staining will be carried out to determine whether Cdc42 is important for EC survival and proliferation. To compien3ent our in vivo studies, Cdc42-null ECs will be isolated and used in the following studies. We will define whether Cdc42 is important for the establishment of cell polarity and directional migration in response to fibronectin gradients. Once a physiological function of Cdc42 in ECs has been determined, then identifying and characterizing the specific downstream effectors of Cdc42 that mediated these effects will be performed. Vascular endothelial growth factor (VEGF) and its receptors, such as VEGF receptor2 (VEGFR2), are crucial for vascular development in vivo, and several lines of evidence indicate that Cdc42 may be involved in the regulation of VEGFR2 homeostasis. To elucidate the molecular mechanisms of angiogenesis defects in Cdc42 EC conditional knockout embryos, we will examine the role and mechanisms of Cdc42 in the regulation of VEGFR2 ubiquitination and endocytosis. These studies will generate not only significant insights into the physiological functions of Cdc42 in vivo, but also critical information for potential new therapies for pathological angiogenesis in the future.
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