Gene Transfer into Murine Stem Cells and Mice Using Retroviral Vectors

Biological processes such as stem cell differentiation and embryonic development are believed to be con-trolled by differential gene expression. The control of gene expression during differentiation and develop-ment is poorly understood, thus the ultimate aim of developmental biology is to study the role of individual genes in these processes in vitro and in vivo. We have decided to study gene regulation in the con-text of embryonal stem cell lines, hematopoietic pre-cursor cells, and in early mouse embryos. All of these systems exhibit a distinct developmental program that can be followed in vitro and in vivo in the whole organ-ism. Because of the lack of developmental mutants available to the mammalian embryologist, gene trans-fer is used to analyze gene regulation. The various ways