The construct and its verification. A) The construct consists of a loxP flanked mCherry cassette, which is driven by the chicken β-actin promotor with CMV enhancer, followed by an intron-eGFP cassette, which will only be expressed after Cre-mediated recombination. Black triangles illustrate the loxP sites. B) Expression of mCherry was validated in HEK-293 cells after transient transfection. Scale bar is 100 μm.