Figure 1. Inducible GFP-TeTxLC expression in SLICK; RC::Ptox mice (A,B).

Schematic representation of the SLICK and RC::Ptox transgenes in SLICK; RC::Ptox compound heterozygous mice before (A) and after (B) induction of Cre-mediated recombination. In SLICK lines, yellow fluorescent protein (YFP) and the tamoxifen-inducible form of cre recombinase (CreER^T2) are co-expressed in populations of projection neurons under control of the Thy1 promoter [5, 23]. The RC::Ptox construct comprises the CAG promoter, a transcriptional “STOP cassette” flanked by loxP sites (triangles), followed by a sequence coding for GFP-TeTxLC and is targeted to the ROSA26 locus [8]. Following Cre-mediated recombination GFP-TeTxLC is expressed in YFP-labeled neurons. Neuronal labeling and recombination is sparse in the SLICK-V line and widespread in SLICK-H. (C) Inducible expression of GFP-TeTxLC assessed by in situ hybridization in SLICK-V; RC::Ptox mice. Sparse expression of TeTxLC mRNA was detected in pyramidal neurons of the subiculum and CA1 regions of the hippocampus in tamoxifen-treated but not untreated SLICK-V; RC::Ptox mice (arrows). (D) Inducible expression of GFP-TeTxLC protein in SLICK-H; RC::Ptox mice detected bywestern blotting for GFP following immunoprecipitation from brain lysates with an anti-tetanus toxin antibody. While not directly detected in cell lysates, GFP-TeTxLC fusion protein (~75 kDa) could be immunoprecipitated from tamoxifen-treated but not untreated control mice (arrow). (E) GFP-TeTxLC protein detected by immunohistochemical staining for GFP in the hippocampus of CaMKII-Cre; RC:Ptox mice. GFP-TeTxLC (brown stain) is visible in cell bodies and dendrites of CA1 pyramidal cells.