I was recording a new BioChat (you should subscribe) recently with a professor at Harvard. We discussed gene therapy in passing for the disease he was studying, and one of the things that he brought up was the need to ensure that whatever therapy is designed has to be safe and effective. This of course is the promise and also the challenge of CRISPR-based research, in which the model is known but the targeting efficiency isn't where it needs to be in order to be of practical use in therapeutics. This is a big reason why the biomedical research world was abuzz with the recent announcement (and preprint) of a major discovery by scientists at the Broad Institute, where they characterized the mechanisms and the potential utility of a system similar to CRISPR in eukaryotes.