“Efficient Genome Editing in Zebrafish Using a CRISPR-Cas System”, Woong Y. Hwang, Yanfang Fu, Deepak Reyon, Morgan L. Maeder, Shengdar Q. Tsai, Jeffry D. Sander, Randall T. Peterson, J-R Joanna Yeh, J. Keith Joung2013 (; backlinks; similar)⁠:

In bacteria, foreign nucleic acids are silenced by clustered, regularly interspaced, short palindromic repeats (CRISPR)-CRISPR-associated (Cas) systems.

Bacterial type II CRISPR systems have been adapted to create guide RNAs that direct site-specific DNA cleavage by the Cas9 endonuclease in cultured cells.

Here we show that the CRISPR-Cas system functions in vivo to induce targeted genetic modifications in zebrafish embryos with efficiencies similar to those obtained using zinc finger nucleases and transcription activator-like effector nucleases.