Development of CRTEIL and CETRIZ, Cre-loxP-Based Systems, Which Allow Change of Expression of Red to Green or Green to Red Fluorescence upon Transfection with a Cre-Expression Vector

Figure 2

Cre-mediated excision in vitro. (a)–(c) NIH3T3 cells transfected with pCRTEIL alone. When cells were inspected for fluorescence 1 day after transfection, HcRed1-derived red fluorescence (but not EGFP-derived green fluorescence) was predominant (indicated by arrows in (b)). (a)–(c) Microphotographs indicate the same cells. (d)–(f) NIH3T3 cells cotransfected with pCRTEIL and pCAG/NCre. Some cells predominantly exhibited green fluorescence (indicated by arrows in (e) and (f)), while other cells exhibited both types of fluorescence (indicated by arrowheads in (e) and (f)). (d)–(f) Microphotographs indicate the same cells. (g)–(j) NIH3T3 cells transfected with pCETRIZ alone. When cells were inspected for fluorescence 1 day after transfection, EGFP-derived green fluorescence (but not HcRed1-derived red fluorescence and lacZ expression) was predominant (indicated by arrows in (h)). (g)–(j) Microphotographs indicate the same cells. (k)–(n) NIH3T3 cells cotransfected with pCETRIZ and pCAG/NCre. Cells exhibited both green and red fluorescence as well as lacZ expression (indicated by arrows in (l), (m), and (n)). (k)–(n) Microphotographs indicate the same cells. (a), (d), (g), and (k) Photographs taken under light (Light); (b), (e), (i), and (m) photographs taken under UV illumination using filters for detection of red fluorescence (HcRed1); (c), (f), (h), and (l) photographs taken under UV illumination using filters for detection of green fluorescence (EGFP); (j) and (n) photographs taken under light after staining with X-Gal (lacZ). Bar: 10 𝜇m.