"Blood and marrow transplantation (BMT) has been used successfully to treat malignant blood disorders and genetic diseases. Although BMT has been effective, problems remain, for example lack of suitable donors and engraftment failure. Cord blood (CB) contains hematopoietic stem cells (HSC) that can be used to transplant children. However, there are too few HSC in most CB samples to reliably engraft adult patients following BMT. Development of HSC expansion prior to transplantation would allow successful engraftment in patients that cannot be transplanted today due to a lack of a suitable donor. While some classical cytokines can maintain the number of HSC in culture, expansion of HSC in vitro will require discovery of novel factors that can increase more symmetrical divisions of HSC. In this project we will identify new factors that can expand HSCs by increasing the proliferation of immature HSC, using recent findings from embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. ES/iPS cells are cell lines that have strong proliferation ability and are pluripotent in the presence of defined factors. Several genes expressed in ES/iPS cells have been identified as stem cell regulators, but a comprehensive analysis of all possible genes is essential to find additional factors that may be important for expansion of HSC. The screening will be done by using microarray analysis, subtraction assay, and over expression using cDNA libraries. Genes that are differentially expressed in immature ES cells and differentiated cells will be inserted into lentiviral vectors and transduced to HSC. The transduced HSCs will be analyzed with respect to inceased stem cell function using a transplantation assay in vivo. Findings from the project are expected to discover several novel regulatory molecules that will allow HSC expansion prior to transplantation. Successful HSC expansion will make most CB donor samples useful for adults requiring HSC transplantation therapy."