The transgene was constructed from a modification of BAC RP24-149-K18 such that a cassette containing an improved cre gene fused to the modified human ESR1 receptor (ERT2) and an IRES-EGFP followed by an frt-flanked neo cassette was inserted at the start of the Slc16a8 open reading frame. Transient flp expression in removed the neo cassette in bacterial cells. Cre activity is detected in the retinal pigment epithelium.