The "loss-of-function" approach to studying gene function in mice has been very successful in recent years. The most commonly used and most informative "loss-of-function" approach is to study the consequence of eliminating a gene in the mouse. This technique, termed gene "knockout", has been well established in the mouse. Analysis of the "knockout" mouse phenotype can allow us to deduce the function of this gene in a biological process. In addition, it offers a genetic toll or model to study complex genetic pathways during development or disease processes.
The most crucial step in creating a knockout mouse is the preparation of the knockout embryonic stem (ES) cell line. This process utilizes homologous recombination to target and replace the endogenous gene with a modified nonfunctional copy. These targeted ES cells are injected into the blastocysts of donor mice. The injected blastocysts are then transferred to the uterus of a pseudopregnant foster mouse. The injected ES cells co-mingle with the ES cells of the inner cell mass of the donor blastocyst. Thus the resulting pup is chimeric, with both the injected and donor cells contributing to the structure of the mouse. Chimeric mice are easily identified by coat color, as the chimeric mouse will have bands of fur displaying the colors of the background donor and ES cells. Please contact Ann Mullin with questions regarding ES cell injections.
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