AAV with eSYN promoter driven FLPo

This AAV expresses FLPo driven by a neuron eSYN promoter.

The eSYN is a hybrid promoter consisting of a 0.4Kb CMV enhancer (E) and the 0.45Kb human Synapsin I promoter fragment (hSYN1). eSYN hybrid promoter gives about 2-4 fold higher expression than that of the parental hSYN1 promoter. However, the neuronal specificity of eSYN is slightly decreased, compared to that of the parental hSYN1 promoter.

FLPo is a codon-optimized version of FLPe that greatly increases the protein expression and the FRT recombination efficiency in mouse cells. FLP is a site-specific recombinase (SSR) from the _ integrase family which recognizes distinct 34 bp FRT sites. Like Cre/LoxP system, the FLP/FRT system has been widely used for gene expression and generating conditional knockout mice, mediated by the FLP/FRT system. Initial use of FLP in mammalian cells revealed inefficient recombinase activity due to thermal instability of the FLP protein. Subsequent screening for thermostable mutants resulted in the identification of FLPe which has a 4-fold higher recombination efficiency at 37oC than original FLP. However, the recombination efficiency of FLPe in cells remains very low relative to other recombinases because of its non-mammalian origin. FLPo is engineered by codon optimization of FLPe, and gives much higher expression and activity than FLPe.