Embryonic stem (ES) cells have the potential to transform our knowledge of human disease and development and give rise to new classes of therapeutic agents – from novel drugs to cell-based therapies. To ensure Canada is strategically positioned to take full advantage of mouse and human ES cell resources, this proposal seeks to identify several key barriers in the current state of ES cell technology and to develop novel technologies to overcome these barriers. The team will execute: 1) development of “Blue Tag” technology that allows plasmid recombineering, 2) development of a new DreO-rox recombinase system for use in vivo, and 3) development of conditional-ready knockout mutations in genes that show specific expression patterns in the brain. The proposed technologies in this project will be developed using mouse ES cells but can be applied by others to any model cell system. These enabling technologies are expected to significantly impact biomedical disease-focused research programs and biotech companies in Canada and thereby increase the rate at which new medical discoveries are moved into health care delivery.