1. Understanding molecular and cellular mechanisms of angioblast specification
It has been hypothesized that endothelial cells and hematopoietic stem cells share common precursor population, the hemangioblasts. Evidences from the in vitro studies and cell culture experiments suggest the existence of these cells. However, it is still not clear whether hemangioblasts exist during normal development, and if so, how these two lineages separate. Using the combination of single cell labeling and lineage tracing, I have recently shown that the hemangioblasts exist during development. In addition, I've shown that Notch signaling appears to negatively regulate endothelial cell differentiation from hemangioblasts. Inhibition of Notch signaling increases the number of endothelial cells by three folds at the expense of hematopoietic stem cells, suggesting that Notch signaling pathway promote hematopoietic stem cell fate over endothelial cell fate in nascent hemangioblasts. I am planning to continue studying the differentiation of hemangioblasts in several known mutant background to investigate the role of various signaling pathways on the segregation of hemangioblast lineage.
2. Molecular and Genetic Analyses of Vascular Specific Mutations
From recently completed screen, several mutations affecting vascular development have been identified. Using flk1:EGFP transgenic lines which expresses GFP in all endothelial cells, we categorized these mutations into four classes: mutations affecting angioblast specification, mutations affecting vascular tube formation, mutations affecting angiogenesis and remodeling process, and mutations affecting maintenance of vasculature. Among these, I am interested in first two classes of mutations. Currently, all mutations are mapped on the respective linkage groups. I will pursue positional cloning of the aforementioned mutants, and analyze their phenotype with molecular, genetic, and biochemical approaches to understand the functions of the loci affected by these mutations during vascular development.
