2010 Annual Report 1a.Objectives (from AD-416) Objective 1: Elucidate the role of vitamin A in vascular development and hematopoiesis using mouse embryos, in vitro assays, and complementary techniques. Sub-objective 1.A. Determine the intracellular mechanism(s) by which endothelial cell migration is regulated during vascular remodeling, and quantify the effects of retinoic acid deficiency on this process. Sub-objective 1.B. Investigate the role(s) of retinoic acid in the specification of yolk sac primitive endothelium to hemogenic endothelium and its differentiation to blood cell lineages. Sub-objective 1.C. Identify and characterize hemogenic endothelium within the aorta-gonad-mesonephros (AGM) region of the embryo, and determine whether retinoic acid regulates its fate and function. Objective 2: Identify target genes downstream of retinoic acid signaling that are required for blood and blood vessel development. Sub-objective 2.A. Determine which endoderm-derived soluble factors, downstream of retinoic acid, regulate endothelial cell migration and enable vascular remodeling. Sub-objective 2.B. Test whether genes downregulated in hemogenic endothelial cells in the absence of retinoic acid signaling mediate the specification of hemogenic endothelium. 1b.Approach (from AD-416) Children's Nutrition Research Center scientists will further investigate, on a cellular and molecular level, the role of retinoid signaling in the regulation of blood vessel formation and hemaotpoiesis. These studies will a employ transgenic mouse models to define the contribution of retinoids to these processes in vivo, and well-controlled cell culture systems to aid in elucidating their cellular and molecular roles in vitro. We will also employ RT-PCR and Microarray approaches to discover genes downstream of retinoic acid signaling that directly regulate blood and blood vessel formation. Information gained from these studies will further the understanding of normal development and the role of nutrients, such as retinoids, therein. 3.Progress Report During FY2010, we have determined the role of retinoic acid in regulating endothelial cell migration during blood vessel formation and remodeling, and determined the signaling pathways downstream of retinoic acid that regulate this process. We have also isolated and characterized specialized hemogenic endothelial cells from the embryo and are now trying to determine how retinoic acid regulates its formation and function during embryonic development. The ADODR monitors activities for the project by routine site visits, and review of major purchases of supplies/equipment, use of SCA funds for foreign travel, and submission of grant applications by investigators funded through the SCA. 4.Accomplishments 1. Impact of Vitamin A on blood vessel development. Researchers are interested in understanding how blood vessels form, and what role specific nutrients play in this process. In these studies, we sought to investigate the signals that regulate the development of the inner layer of blood vessels, called endothelial cells. Researchers at the Children's Nutrition Research Center, Houston, Texas, found that Vitamin A (retinoic acid) not only regulates the growth of endothelial cells, but also regulates their ability to move (migrate) and organize into blood vessel structures. We found that Vitamin A is critically important for blood vessels to form and grow, and we also defined the biological pathway that is regulated by Vitamin A to control endothelial cell behavior. From this work, we gained a better understanding of the cellular role of Vitamin A in the process of blood vessel formation, which was previously unknown. This advances the field of vascular development and provides more insight into human defects resulting from Vitamin A deficiency.