Quoting from the first reference:
"targeting of Cas9 to specific genomic sites is mediated by a 20 nucleotide guide sequence within an associated CRISPR RNA (crRNA) and requires a trans-activating crRNA (tracrRNA) that recruits the crRNA into the Cas9 complex (3<http://www.biotechniques.com/BiotechniquesJournal/2014/September/Precise-gene-deletion-and-replacement-using-the-CRISPRCas9-system-in-human-cells/biotechniques-353874.html#CIT0003>). "
In English: There is a 20 nucleotide sequence that is recognized by the crRNA allowing targeted gene activation. This means that out of the billions of nucleotides in our genome (of which there are multiple repeats of certain 20 nucleotide sequences) those specific 20 are recognized. That's been possible for a couple of decades and it's really cool but it's not specific enough to avoid unintended insertions.
"It is notable that a single guide RNA (gRNA) that mimics the tracrRNA-crRNA complex can recruit Cas9 to targeted genomic sites and generate double-stranded breaks (DSBs) in DNA (5<http://www.biotechniques.com/BiotechniquesJournal/2014/September/Precise-gene-deletion-and-replacement-using-the-CRISPRCas9-system-in-human-cells/biotechniques-353874.html#CIT0005>)."
In English: This cas9 mechanism is used by bacteria to break foreign DNA, and the authors of the biotechniques paper are using it to cleave our DNA. (Is this good?)
"Our results illustrate that the CRISPR/Cas9 system can be used to precisely and effectively generate targeted deletions or gene replacement in human cells, which will facilitate characterization of functional domains in protein-coding genes as well as noncoding regulatory sequences in animal genomes."
Translation: They haven't done it yet, they just brag about it. In fact, they don't propose its use for GMO AT ALL, instead they say they are ready to use it to identify functional nucleotide sequences, a purpose I applaud as worthy and non-risky.
Conclusion: Not ready for prime time in the field.
Christina
Christina Wahl, Ph.D.
Department of Biomedical Sciences
Cornell College of Veterinary Medicine
Ithaca, NY 14853
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