Cheng, Z. et al. Nat. Biotechnol. 10.1038/nbt.2674 (18 August 2013).

Transcription activator–like effector (TALE) proteins fused to the Fok1 endonuclease have been used to make targeted mutations in the genomes of several species. Cheng et al. now demonstrate conditional gene editing with these TALE nucleases (TALENs) in Caenorhabditis elegans. They generate transgenic worms in which TALENs designed to target genes of interest are under the control of cell type–specific promoters. They thereby determine the focus of action of specific genes (that is, the cells in which the gene product must be mutant to confer a phenotype), and they study the function of essential, embryonic lethal genes in post-embryonic processes. This approach should prove useful for dissecting gene function in the worm.