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SCIENTIFIC DISCOVERY AND THE FUTURE OF MEDICINE
Biology and clinical medicine are in the midst of a remarkable revolution. Technical advances in DNA sequencing have given scientists access to the molecular code governing each individual’s unique characteristics, including disease susceptibility and drug sensitivity. This remarkable knowledge could only inform researchers and clinicians because tools to act on the data by making targeted changes to the human genome were too expensive and cumbersome for widespread practical use. Nonetheless, the compelling promise of truly personalized medicine spurred the quest for methods to achieve precision genomic manipulation.
In an interesting twist of scientific fate, basic research on an adaptive immune system in bacteria led to the breakthrough genomic engineering technology known as CRISPR-Cas9. Experiments focused on understanding how bacteria acquire resistance to viruses, using genomic loci known as clustered regularly interspaced short palindromic repeats (CRISPR), uncovered the activity of the CRISPR-associated (Cas) RNA-guided DNA-cleaving enzyme called Cas9. Cas9 generates double-stranded DNA breaks at sites matching the sequence of a guide RNA molecule that was designed in the laboratory to include features necessary for both Cas9 binding and DNA recognition (Figure).1 When introduced into animal cell nuclei, the Cas9 protein and RNA-guided complexes trigger site-specific genome editing by generating double-stranded DNA breaks that are repaired by the cell’s natural machinery.