Classic gene targeting and transgenic approaches have been used in this lab to produce new lines of genetically modified mice (see 1996 and 2000 references). One limitation of traditional transgenesis for ectopic expression of genes in airways of mice is that cell/tissue-specific promoters commonly used are highly susceptible to position effects that impact specificity and level of expression. To overcome these problems we have validated an innovative strategy that involves targeting transgenes into the HPRT locus (see “Single-copy transgenic mice with chosen-site integration”, PNAS 93:9067-9072, 1996 from the lab of Dr. Oliver Smithies). Targeting one or more transgenes to this locus is accomplished through use of an HPRT replacement vector, developed by Dr. Smithies. For an example of a new line, bred to inducibly express GFP-tagged proteins specifically in the nuclei of the airway epithelial cells, see the photo of the dissected lung lobe on our homepage!

We are in the process of using this method to achieve consistent levels of drug-regulated transgene expression for a variety of mutant forms of beta-catenin and other genes of interest. These models will allow us to elaborate on exciting results in which potentiation of canonical Wnt signaling leads to stabilization of the bronchiolar stem cell phenotype (see Reynolds et al., 2008 in references).