Year 2

The goal of our research is to understand the role of Eph/ephrin signaling in the proliferation or differentiation of human embryonic stem cells (hESCs). Ephs and ephrins are cell contact dependent signaling molecules and have been shown to be important for stem cell differentiation decisions during the development of many structures in the mouse, including the brain, pancreas, and intestine. Our hypothesis is that these molecules will also be used in many differentiation decisions in the human. Additionally, because these proteins are on the cell’s surface they can be used to purifiy specific cell types. In the last year we have differentiated hESC into neurons, as assessed by morphological characterization and expression of marker proteins. We have found that multiple members of the Eph/ephrin signaling family change expression patterns during neuronal differentiation. We have made polyclonal antibodies against one of these, and found that it is expressed in subsets of hESCs. Our hypothesis is that this protein is important for cell-cell contact dependent signaling within a stem cell colony that is used to keep cells in the stem fate. We are currently testing this hypothesis by treating hESCs with agonists of ephrin signaling and assaying for changes in differentiation.