Figure 1

Conditional expression systems in the rat brain. (A) Tet regulatory system. Schematic outline of the constructs used to generate the transgenic rat lines CaMKIIa-tTA and EGF-Ptetbi-luc rats. The CaMKIIa promoter fragment is used to drive expression of the transcriptional activator tTA, which binds in the absence of doxycycline (Dox) - but not in its presence - to the tetO containing bidirectional minimal promoter Ptetbi. tTA binding activates Ptetbi and leads to the simultaneous expression of the reporter genes EGFP and luciferase (luc). (B) CreERT2 inducible gene expression system. Schematic outline of the transcription units incorporated in the CaMKIIa-CreERT2 and CAG.loxP.EGFP rat lines. In double transgenic CaMKIIa-CreERT2/CAG.loxP.EGFP rats, the CaMKIIa promoter fragment controls expression of the tamoxifen-inducible Cre recombinase CreERT2. The Cre reporter transgene is based on a CAG promoter controlled transcriptional unit, in which the lacZ gene (nlacZ, with nuclear localization signal) serves as a STOP fragment to prevent transcription of the posterior gene EGFP. In the non-recombined configuration, lacZ is broadly expressed but replaced by EGFP when Cre-mediated recombination deletes the loxP-flanked STOP fragment. Dox: doxycycline hydrochloride; EGFP: enhanced green fluorescent protein; luc: luciferase; tTA: tetracycline-controlled transactivator.