Ai3 mice hemizygous for this Rosa-CAG-LSL-EYFP-WPRE conditional allele are viable and fertile. A loxP-flanked STOP cassette prevents transcription of the downstream enhanced yellow fluorescent protein (EYFP). When bred to mice that express Cre recombinase, the resulting offspring will have the STOP cassette deleted in the cre-expressing tissue(s); resulting in expression of EYFP. Because this CAG promoter driven reporter construct was targeted for insertion into the Gt(ROSA)26Sor locus, EYFP expression is determined by which tissue(s) express Cre recombinase. The donating investigator reports that Ai3 mice do not express EYFP prior to introduction of Cre recombinase and EYFP expression following exposure to cre can be detected by fluorescence, mRNA (in situ hybridization) and antibody staining (immunohistochemistry). These Ai3 mice are useful as a Cre reporter strain; expressing enhanced yellow fluorescent protein following Cre-mediated recombination. 
 For characterization information, see images at the Allen Institute for Brain Science website (<a href="http://connectivity.brain-map.org/transgenic/imageseries/list/1.html?gene_term=Ai3">Ai3 images</a>). 
 Of note, the FRT sites flanking the mutation allow for additional targeted replacement of the reporter sequences through Flp-mediated recombination if so desired. 
 Similarly, the attB/attP-flanked selection cassette may be removed by introduction of the site-specific bacteriophage PhiC31 integrase if so desired.

These Ai3 mice harbor a targeted mutation of the Gt(ROSA)26Sor locus with a loxP-flanked STOP cassette preventing transcription of a CAG promoter-driven enhanced yellow fluorescent protein (EYFP), and may be useful as a Cre reporter strain. EYFP is expressed following Cre-mediated recombination.

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