Six2-TGCtg mice harbor an ~181 kb BAC transgene with a Tet-off-eGFPCre under control of the Six2 promoter/enhancer regions within the BAC transgene. The Tet-off-eGFPCre contains both the tetracycline-controlled transactivator protein (tTA) as well as the tetracycline operator (tetO; also called tetracycline-responsive element [TRE] or tet-operator) upstream of an EGFPCre fusion protein, however this strain is not useful as a Tet-Off tool (see below). Tet-independent expression of the eGFPCre fusion protein (EGFP immunofluorescence and direct fluorescence/Cre recombinase activity) is directed to nephron progenitor population cap mesenchyme from the onset of metanephric kidney development. When bred with mice containing a loxP-flanked sequence of interest, Cre-mediated recombination will result in deletion of the floxed sequence(s) in such tissues of the offspring. These Six2-TGCtg mice may be useful as fluorescent or Cre-lox tools for lineage-tracing/marking Six2-expressing cells for studying multipotent nephron progenitor cell populations throughout kidney organogenesis. Hemizygous Six2-TGCtg mice are viable and fertile. The donating investigator reports they were unable to produce homozygous mice from hemizygous matings. The Jackson Laboratory 2024, used with permission.