Msi1^{tm1.1(cre/ERT2)Njen}

Sequences of the first exon downstream of the initial ATG of Msi1 in a BAC clone (RP23-268H8) were replaced with a cre/ERT2 cassette, poly A signal and Frt-flanked PGK-neo, by recombineering in bacterial cells. The targeting construct was transfected into B6/129 F1 ES cells. Targeted ES clones were injected into C57BL/6 blastocysts to generate chimeras. Germline mutants were bred to FLPe mice to remove the neo selection cassette. RT-PCR demonstrated that no transcript containing exon 1 is produced from the mutated allele. (J:194120)