Highly B lymphocyte‐specific tamoxifen inducible transgene expression of CreERT2 by using the LC‐1 locus BAC vector

The generation of cell type specific inducible Cre transgenic mice is the most challenging and limiting part in the development of spatio-temporally controlled knockout mouse models. Here we report the generation and characterization of a B lymphocyte-specific tamoxifen-inducible Cre transgenic mouse strain, LC-1-hCD19-CreERT2. We utilized the human CD19 promoter for expression of the tamoxifen-inducible Cre recombinase (CreERT2) gene, embedded in genomic sequences previously reported to give minimal position effects after transgenesis. Cre recombinase activity was evaluated by cross-breeding the LC-1-hCD19-CreERT2 strain with a strain containing a floxed gene widely expressed in the hematopoietic system. Cre activity was only detected in the presence of tamoxifen and was restricted to B lymphocytes. The efficacy of recombination ranged from 27 to 61% in the hemizygous and homozygous mice, respectively. In conclusion, the LC-1-hCD19-CreERT2 strain is a powerful tool to study gene function specifically in B lymphocytes at any chosen time point in the lifecycle of the mouse. genesis 47:729–735, 2009. © 2009 Wiley-Liss, Inc.