Isolation of Novel CreER(T2)-Driver Lines in Zebrafish Using an Unbiased Gene Trap Approach

Gene manipulation using the Cre/loxP-recombinase system has been successfully employed in zebrafish to study gene functions and lineage relationships. Recently, gene trapping approaches have been applied to produce large collections of transgenic fish expressing conditional alleles in various tissues. However, the limited number of available cell- and tissue-specific Cre/CreER(T2)-driver lines still constrains widespread application in this model organism. To enlarge the pool of existing CreER(T2)-driver lines, we performed a genome-wide gene trap screen using a Tol2-based mCherry-T2a-CreER(T2) (mCT2aC) gene trap vector. This cassette consists of a splice acceptor and a mCherry-tagged variant of CreER(T2) which enables simultaneous labeling of the trapping event, as well as CreER(T2) expression from the endogenous promoter. Using this strategy, we generated 27 novel functional CreER(T2)-driver lines expressing in a cell- and tissue-specific manner during development and adulthood. This study summarizes the analysis of the generated CreER(T2)-driver lines with respect to functionality, expression, integration, as well as associated phenotypes. Our results significantly enlarge the existing pool of CreER(T2)-driver lines in zebrafish and combined with Cre–dependent effector lines, the new CreER(T2)-driver lines will be important tools to manipulate the zebrafish genome.