Mostly, CRISPR/Cas9 reduces the cost of getting a custom endonuclease (molecular scissors that cut DNA at particular sequences). It is several orders of magnitude cheaper than alternatives, and it is also incredibly quick to set up! This makes it much easier to try more experiments. Also dCas9 (partly or wholly disabled Cas9) can be used to make the system the basis for multiplex gene targeting experiments that can be used to induce entirely new regulatory networks in one step! Wow!
So there is a lot of good but don't forget your question: haven't we had this for a long time? Yes, the techniques are fundamentally the same as others which have been used for a long time. Endonuclease and homologous repair are standard tools in genome engineering. It just costs much less to design custom endonuclease now. It seems like there is a bit too much hype about CRISPR/Cas9 techniques as genome engineering tools--- we are engineering genomes in exactly the same way as before. The scissors have changed but the glue is still endogenous to the organisms that we are engineering.
To my knowledge there has only been one case in which DNA was shipped as code to be the genome of a dead cell. Maybe someday we will be able to write large genomes. Until then nearly all the editing we do will be in living organisms, as it has been forever (even before CRISPR/Cas9).
Well said. I'll add some scientific esoterica, because it parallels software a little: we've even had custom endonuclease services for a while (TALENS[1]), which serve a very similar function. But they were hard to generate and difficult to work with. Companies like Invitrogen even sold a TALEN-making service, costing in the dozens-of-thousands of dollars to generate a TALEN for preclinical drug discovery use.
Then CRISPR came along. It was like the open-sourced, better-performing alternative to the cumbersome, proprietary software. Switching was a no-brainer, and it has handily become the future, if not the mainstream already.
Right. My own PhD work was on designing custom transcription factors to bind to specific sequences (not even with TALENs- it tried to do full molecular dynamics to predict the binding constant for multiple different DNA sequences, which was absurdly expensive). It would have to be re-engineered once for each sequence; with CRISPR, you just provide a matching template sequence.
But CRISPR/Cas9 is not open source. It is proprietary! A half billion year old natural system has been slightly tweaked and is now owned by the discovering groups. It is free for research use and for commercial purposes might still be quite expensive.
So there is a lot of good but don't forget your question: haven't we had this for a long time? Yes, the techniques are fundamentally the same as others which have been used for a long time. Endonuclease and homologous repair are standard tools in genome engineering. It just costs much less to design custom endonuclease now. It seems like there is a bit too much hype about CRISPR/Cas9 techniques as genome engineering tools--- we are engineering genomes in exactly the same way as before. The scissors have changed but the glue is still endogenous to the organisms that we are engineering.
To my knowledge there has only been one case in which DNA was shipped as code to be the genome of a dead cell. Maybe someday we will be able to write large genomes. Until then nearly all the editing we do will be in living organisms, as it has been forever (even before CRISPR/Cas9).