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. Author manuscript; available in PMC: 2012 Sep 5.
Published in final edited form as: Prog Brain Res. 2012;196:193–213. doi: 10.1016/B978-0-444-59426-6.00010-0

Figure 1.

Figure 1

Single transgenic approaches to expressing optogenetic tools (using ChR2 as an example). (A) Conventional transgenic approach, in which an expression cassette contains a promoter and the transgene and is randomly integrated into the genome. GS Pr, gene-specific promoter. pA, polyA signal. (B) Gene trap approach, in which a promoterless cassette containing the transgene is randomly integrated into the genome, and the transgene expression is determined by a “trapped” nearby endogenous promoter. SA, splice acceptor. Black boxes indicate endogenous gene exons. (C) BAC transgenic approach, in which the transgene is inserted into the locus of the gene-of-interest contained within a BAC clone, and this BAC clone is randomly integrated into the genome. (D) Knock-in approach, in which the transgene is targeted to the endogenous locus of the gene-of-interest by homologous recombination. The targeting site can be either at the ATG start codon (upper panel), or at the STOP codon (lower panel).