Expression of Cre recombinase in retinal Muller cells

Purpose: In an effort to generate inducible RPE-specific Cre mice using a 3.0-kb human vitelliform macular dystrophy-2 (VMD2) promoter, we identified a mouse line with unanticipated Cre activity in the neural retina, including Miller glial cells. Miller cells play important roles in the function and maintenance of the retina, and this mouse line would be potentially useful for conditional gene targeting in Muller glia. We therefore characterized the timing, inducibility, and cell specificity of Cre expression, as well as Miller cell-specific efficiency of Cre-mediated recombination in this mouse line. Methods: Transgenic mice carrying cassettes of human P-VMD2-rtTA and TRE-cre were generated. Cre expression was characterized using a Cre-activatable lacZ reporter mouse line (R26R) and a floxed interleukin six signal transducing receptor (gp130) mouse line. Results: p-Galactosidase (p-gal) assay and immunohistochemical analysis of VMD2-cre/R26R double transgenic mice indicated that Cre activity was detected in cells located in the inner nuclear layer, with prominent expression of p-gal in Miller cells. Cre activity was also detected in photoreceptors in the outer nuclear layer. PCR analysis demonstrated that Cre-mediated recombination initiated by embryonic day 15. Immunohistochemical analysis indicated that Cre-mediated deletion of floxed gp130 gene occurred in 52% of the retinal Miller cells. Retinal function and morphology were normal in 10-month-old VMD2-cre mice. Conclusion: We generated a transgenic cre mouse that is useful to study gene activation and inactivation in retinal Miller cells. (C) 2009 Elsevier Ltd. All rights reserved.