Figure 2. BAC transgenic Kir4.1-CreER^T2 mice do not exhibit tamoxifen-independent expression.

A, A CreER^T2-polyA construct, together with a Rox-flanked spectinomycin selection cassette, was cloned upstream of the ATG of the Kir4.1-encoding gene KCNJ10 (NCBI reference sequence NP_001034573.1) in the RP24–295K5 BAC by homologous recombination (HR). PiggyBAC inverted terminal repeats (ITRs) were inserted by HR into the BAC backbone flanking the genomic insert of CreER^T2 (gene of interest or GOI) in order to facilitate the transposase-mediated integration of the targeted BAC into the host genome. B, Timeline of tamoxifen (TMX) administration schemes utilized in this study and the correlated stages of Schwann cell development. C, tdTom expression was not observed in L1-labeled sciatic nerve sections (left two panels) or AlexaFluor 488-conjugated α-BTX-labeled diaphragm whole mounts (right tow panels) of adult Kir4.1-CreER^T2, conditional tdTomato mice (Kir4.1-tdTomato) in the absence of TMX treatment. D, Most S100β-labeled SC isolated from the sciatic nerves of P0 Kir4.1-tdTomato mice whose mothers were injected with TMX at E17.5 and E18.5 exhibit tdTom expression (left three panels). Percentage of S100β-labeled SC expressing tdTom after embryonic TMX administration at E17.5 and E18.5 (E17.5) or at E15.5 (right panel); data in text.