AAV with hRPE(0.8) promoter driven iCre

This AAV expresses iCre driven by a retina hRPE(0.8) promoter.

The RPE65 gene encodes a protein of the retinal pigment epithelium (RPE) with a key role in the cycling of retinoids. It was shown that a RPE promoter of about 0.8 Kb was sufficient to direct high RPE-specific expression in transgenic mice. The 1.5Kb version of the promoter hRPE(1.5), also gives RPE-specific expression, but the expression level is not as high as the 0.8Kb promoter. This is probably due to a negative regulatory element(s) present in the 1.5Kb promoter.

Cre is a recombinase from the P1 bacteriophage. This enzyme carries out site-specific recombination between two DNA recognition sites (LoxP sites) through a topoisomerase I-like mechanism. The Cre recombinase here has been codon-optimized leading to a higher level of Cre protein expression (iCre). The 34base pair (bp) loxP recognition site, ATAACTTCGTATA ATGTATGC TATACGAAGTTAT, consists of two 13 bp palindromic sequence which flank an 8 bp spacer region. The products of Cre-mediated recombination at loxP sites are dependent upon the location and relative orientation of the loxP sites. For example, two separate DNA species both containing loxP sites can undergo fusion as the result of Cre-mediated recombination. DNA sequences found between two loxP sites on the same DNA molecule are said to be floxed. In this case, the products of Cre-mediated recombination depend upon the orientation of the loxP sites: DNA found between two loxP sites oriented in the same direction will be excised as a circular loop of DNA, whereas DNA between two loxP sites that are oriented oppositely will be inverted. Besides LoxP sites, other Lox sites have been designed and tested, such as Lox272 and LoxN etc. These Lox elements have been widely used for genetic studies.