Our project goal is to develop and test a tool that will allow the identification of stem cell-specific genes and genes that are unique to cells made by stem cells. We have made progress in applying this technique to cells grown in culture and have made the tools necessary to identify genes expressed in specific cell types using a cell culture model of nervous system development. We have also made mice that prove this technique works in genetically-manipulated mice. These mice provide important proof-of-principle results, laying the foundation for the development of additional mouse strains that can be used to identify gene expression in stem cells and other cells of interest in their normal, in vivo, setting. We have also shown that we can selectively purify the mRNAs of genes expressed in the brain and other tissues of the mouse.