Embryonic stem cell-based technology to study gene function in the mouse

Mouse embryonic stem (ES) cells have revolutionized gene function studies in the mouse. Manipulation of the ES cell genome and in vitro screening allow for generation of precisely engineered genomic alterations including control of transgene integration position and copy number. Improvement of ES cell technology is the focus of the following work. A mouse line expressing Cre recombinase in a neuron-specific manner was established by placing Cre under the control of the endogenous tau locus. Characterization of this mouse line revealed that tissue-specific reporter expression is achieved; however, this mouse line should be used with caution. A novel site-specific integrase called &phis;C31 was added to the toolbox of site-specific recombinases. Extensive characterization of the system revealed that high integrase expression level is important for recombination. The results suggest a mechanism for &phis;C31 function and a new approach to make &phis;C31 integrase a useful tool to study gene function in mouse.