Ligand-Controlled Site-Specific Recombination in Zebrafish.

Cre-mediated site-specific recombination has emerged as an indispensable tool for the precise manipulation of genomes allowing lineage-tracing studies, temporal and spatial misexpressions, and in particular the generation of conditional knockout alleles. Previously, we and others showed that Cre and its ligand-inducible variant CreERT2 are also highly efficient in the developing and adult zebrafish. The number of Cre driver and effector lines is currently still limited in zebrafish. However, the recent advent of novel genome editing tools such as TALEN and CRISPR/Cas will significantly increase interest in the conditional Cre/lox-technology in this organism. The considerations of basic transgene design and subsequent transgenesis have been addressed elsewhere. Here we outline practical experimental steps for transient functionality tests of CreERT2 driver and effector constructs. In addition, we introduce detailed protocols to elicit CreERT2 -mediated recombination in vivo at embryonic as well as adult stages.