A targeting vector was designed to insert a CreERT2 fusion gene (Cre-ERT2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain), an SV40 polyA signal, and an frt-flanked neo cassette into the initiation codon of the neuronal nitric oxide synthase 1 locus (Nos1). This construct was electroporated into C57BL/6;129S-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts and chimeric mice were bred with 129S mice to originate the colony. Mutant mice were bred with Actin-FLPe mice to remove the neo selection cassette and the FLPe transgene was subsequently bred out of the line.
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