Cxcr4^{tm1.1(cre/ERT2)Stum}

The targeting vector consisting of fragments of 2.9 kb, 3.8 kb and 3.3 kb in size containing the distal promoter sequence, the sequence upstream of exon 1, and the sequence downstream of exon 1, respectively, were used to insert a CreER(T2)-IRES-EGFP cassette and an FRT-flanked neomycin cassette in the 5 end of the 3.3-kb fragment. The linearized construct was electroporated into C57BL/6J mouse ES cells. The neomycin cassette was removed by breeding with C57BL/6J mice expressing Flp-recombinase. With CreER inserted into exon 1, Cxcr4CreER does not produce functional Cxcr4 and homozygous mice bearing this allele are fully deficient in Cxcr4, as verified by immunohistochemistry. (J:288822)