A transgenic construct containing the MCM sequence (cre recombinase fused to two mutated mouse estrogen receptors) with a 3xFLAG (3F) epitope tag at the N-terminus was inserted after the initial ATG in exon 2 of Dppa3 by BAC recombineering. The construct also included the SV40 polyadenylation signal. 2 further rounds of Red/ET recombination resulted in the deletion of genes upstream (Gdf3, Apobec1, Aicda, and Mfap5) and genes downstream (Gm8460, Gm10224, Nanog, and Slc2a3) of Dppa3 in the BAC clone. The final construct contained 16 kp upstream sequence and 18 kb downstream sequence of the Dppa locus and was injected into pronuclei of B6DBA F2 zygotes. Two lines with copy numbers of 4 were analyzed and produced similar results. Line 4 was established. Lines with low copy numbers did not demonstrate efficient recombination.