B-LYMPHOCYTE-SPECIFIC, CRE-MEDIATED MUTAGENESIS IN MICE

Adaptation of the P1 phage-derived Cre/loxP site-specific recombinatio n system to the gene targeting technique allows for the conditional de letion of genes in mice. To selectively modify genes in B lymphocytes, we have generated mice (designated CD19-Cre) which express cre under the transcriptional control of the B lineage-restricted CD19 gene. In a model system involving the cross of CD19-Cre mice with mice bearing a loxP-flanked substrate, we find a deletion efficiency of 75-80% in b one marrow-derived pre-B cells that increases to 90-95% in splenic B c ells.