An enhancer trap transgenic approach was used to generate these mice. The hsyn-bgi-cre:ERT2-bGHpA transgene was designed with the human synapsin minimal promoter (hsyn) minimal promoter driving an icre-ERT2 fusion gene (a codon-improved cre recombinase sequence fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain). A beta globin intron separates the promoter from the cre gene and the bovine growth hormone polyadenylation signal follows the cre sequence. This transgene was injected into C57BL/6J embryos. Founder line 10727 was established on a C57BL/6J genetic background.