Transgenic expression of Cre recombinase in mouse photoreceptors

Abstract

Abstract: : Purpose: To facilitate photoreceptor–specific gene targeting using the Cre–lox system in mice, we aim to produce transgenic mouse lines that express Cre recombinase only in retinal photoreceptors. Methods: Transgenic founder mice harboring a codon–corrected Cre recombinase cDNA (iCre) whose expression is driven by a 4.0 Kb mouse opsin promoter fragment were generated by pronuclear injections. The expression of the Cre recombinase is examined by immunoblotting and immunocytochemistry. The gross morphology of the retinas is examined by plastic semi–thin sections at various postnatal ages. Results: We obtained 15 founders from 400 injected embryos. Ten founders transmit the transgene to their offspring. Five founder lines expressed varied amounts of Cre recombinase exclusively in the outer nuclear layer. We examined the gross morphology of two founder lines with high level of Cre recombinase and found no signs of photoreceptor degeneration up to two months of age. Conclusions: These iCre transgenic mice are useful for photoreceptor–specific gene targeting experiments and should facilitate functional assessments of many essential genes in the context of photorecetpor biology.

Keywords: gene/expression • genetics • photoreceptors