AAV with eSYN promoter driven Cre Inducible hChR2(C128S/D156A)-mCherry

This AAV expresses DIO-hChR2(C128S/D156A)-mCherry 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.

hChR2 is a humanized version of ChR2 for mammalian expression. Wild-type ChR2, as well as a few of its mutations, provides the fastest excitation of the channelrhodopsins offered, and is widely used in in optogenetics techniques in neuroscience. hChR2(D156) mutant is another SFO mutation with a 6.9-minute open-state lifetime, and hChR2(C128S/D156A) double mutation creates a Stabilized Step Function Opsin (SSFO) with a stability of the active state up to 30 minutes.

In the DIO scenario, the transgene of interest is inserted in reverse orientation relative to the 5' promoter and is flanked by oppositely oriented loxP and lox2272 sites. In the absence of Cre expression, the transgene will not be produced. In the presence of Cre expression, the transgene will be "FLip-EXchanged" or FLEXed, leading to expression of the transgene. This is due to a permanent Cre-mediated recombination/inversion of the flanked transgene. This arrangement is called DIO (double-floxed inverse ORF), Cre-ON, Flex-rev (reverse), Flex-ON/FlexON, or DIO-AAV/AAV-DIO (double-floxed inverse ORF in AAV).