This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. These studies focus on conditioning therapy (busulfan) for transplant of autologous transduced hematopoietic stem cells. Busulfan produces a specific loss of early stem cells and has been used as a stem cell cytotoxic conditioning agent prior to bone marrow transplantation in humans.