Figure 1

<p>(A) Targeting strategy for generating mice in which tamoxifen-inducible Cre is expressed from the endogenous Rax locus (<i>Rax-CreER^T2</i>). The targeting vector containing a tamoxifen-inducible Cre (CreER^T2) and pGK-neo cassette flanked with Frt sites was inserted six nucleotides downstream from the start of the initiator codon of the endogenous <i>Rax</i> locus. After homologous recombination, the correct 3′ integration was tested in embryonic stem cells (ES) by PCR using a forward primer (P2) inside the second intron of <i>Rax</i> gene and a reverse primer (P1) in the neo cassette generating a 3 kb fragment. The Rax-CreER^T2-neo mice were later mated with FLPeR mice to remove the neo cassette. Frt, Flp recombinase targets. (B) Correct insertion was confirmed by Southern blot using a 5′ probe which hybridized upstream of the long arm of double digested (AfIII and SexAI) DNA from ES cells. Duplicate samples of heterozygous and wildtype mice are shown. (C) Schema for <i>Rax</i>-regulated Cre-mediated Tdtomato expression induced by 4-OHT.