The transgene was designed with a cre recombinase (and nuclear-localization signal) sequence on one side and an enhanced green fluorescent protein (EGFP) sequence on the other side of a bi-directional tet-responsive promoter (tetO; also called tetracycline operator, or tetracycline-responsive element (TRE)). This transgene was microinjected into C57BL/6J embryos and mice from founder line 2 were bred to C57BL/6J inbred mice. (J:151755)