Our work will focus on understanding the changes that cells undergo during regeneration of a damaged organ. We have chosen the freshwater planaria, Schmidtea mediterranea as our model system, because these flatworms exhibit remarkable regenerative ability due to their pluripotent adult stem cells (neoblasts) that can give rise to all cell types in the body. This work is being undertaken in close collaboration with Dr. Alejandro Sanchez (U. Utah). We are developing a series of assays using planaria to dissect the cell biological processes involved in the repair of organs. Our test organ is planarian photoreceptors. We have worked out an assay that involves laser ablation to specifically destroy photoreceptors, and have shown that these cells regenerate and recover their function. We will further determine the roles of stem cells in photoreceptor repair. Most importantly, we are developing methods to make transgenic planaria that express fluorescent proteins in their stem cell population. We hope to visualize the repair dynamics of photoreceptors and track the cellular behavior of adult stem cells with time lapse microscopy. In the long term, live cell imaging and in combination with RNAi and planarian sequenced genome will allow us to understand the cellular and molecular controls of photoreceptor regeneration at a molecular level. We expect that our studies on planarians will shed light on human stem cells and how to promote regeneration of damaged human organs.