Hprt1^{tm335(Ple277-icre/ERT2)Ems}

The transgene consists of a RP11-990.K4 human bacterial artificial chromosome (BAC) retrofitted to contain a human HPRT complementary sequence (containing exon 1, intron 1, exon 2 and part of intron 2), a mouse 3' Hprt homology arm, an I-Sce linearization cut site, and a mouse 5' Hprt homology arm; all inserted into the sacB gene in the BAC vector. Next, an iCre/ERT2 fusion gene, an intron, an SV40 early polyA signal and a 48-bp full Frt (Ffrt) site-flanked kanamycin resistance (Kan) cassette were inserted directly at the ATG of the human HTR1B locus. Transient transfection with FLP recombinase removed the Kan cassette before the modified BAC was used for targeting as a single copy "knock-in" into the upstream region of the Hprt locus. (J:270567)