The Nestin-cre/ERT2 transgene was designed with the rat nestin (Nes) promoter driving expression of a CreERT2 fusion gene (cre/ERT2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand-binding domain). The transgene was microinjected into fertilized C57BL/6J oocytes, and line K was established.