The transgene was made using BAC RP23-353N18 with the improves cre recombinase gene inserted downstream of the Hdnr beta isoform transcriptional start site. The transgene was inserted into a ROSA26R-lacZ reporter harboring mouse embryonic stem cell lines (mESCs). From these mESCs, embryos were generated by tetraploid morula aggregation and
analyzed in three embryos derived.