Advances in the use of hematopoietic stem cells for transplantation and gene therapy have increased the urgency for a better knowledge of the molecular control of their development and proliferation. An understanding of the molecular processes involved in the earliest stages of stem cell development, currently poorly understood, would provide very useful guide to the selection, expansion and ex-vivo manipulation of stem cells. Our long-term objective is to identify, clone and investigate these genes. An in vitro assay is now available which allow totipotent murine embryonic stem (ES) cells to develop into hematopoietic cells. This transition must involve the activatiOn of the earliest genetic program for initiating hematopoiesis. By comparison with mRNA species from ES cells that are not differentiating into hematopoietic cells, these mRNA may be detected and cloned. A new PCR-based technique has made it possible to obtain """"""""differential display"""""""" of mRNA species between two population of cells. We will combine these two technological advances to identify and clone cDNAs of stem cell related genes which could include receptors, transcriptional factors, adhesion molecules and structural protein unique and specific to hematopoietic cells. Together they should have a wide range of potential application technologically and commercially.
