Applications & Implications
CRISPR is used to induce changes including insertions, deletions, point mutations and rearrangements in the genomes of organisms. It can be utilized to “Knock-out” target genes in various cells/organisms by co-expressing the unique gRNA and Cas9; it is critical that the target is present immediately upstream of the PAM or Protospacer Adjacent Motif sequence, which is specific to the species of Cas9 used. The Cas9 enzyme can be modified to use the system to:
- Selectively activate/repress target genes
- Purify specific regions of DNA
- Image live cells and
- For genome-wide screening
- CRISPR-modified mushrooms resistant to browning were the 1st CRISPR-edited products to be marketed; these are not USDA regulated.
- The pig genome has been edited in 62 places at once (eGenesis, Boston, MA)
- Transgenic pigs have been generated for lung transplants (United Therapeutics, Silver Springs, Maryland). However, there is a concern of potential transmission of pig diseases in immunocompromised persons.
- The NIH is currently reviewing its 1st HGT protocol utilizing the CRISPR technology for T-cell therapy.
- The gene editing technology has elicited a furious debate about whether and how it might be used to modify the genomes of human embryos, breaching an ethical line that has typically been considered not crossable. No one has so far showed an interest in producing live babies with edited genomes; initial experiments suggest that it is not yet safe but it is simply a matter of time. There are concerns with human germline modification:
- Sun Yat-sen University, China, April 15, 2015 first used the CRISPR system in non-viable tripronuclear human embryos to modify the beta-thalassemia gene. High rate of off-target mutations was noted.
- UK, Feb. 1, 2016: human embryos and Cas9 technology first used for early developmental study. Experiments were required to stop after 7 days of embryonal development and the embryos had to be destroyed.
- China, April 6, 2016: human tripronuclear- embryos were used to edit the CCR5 gene in HIV research. No off-target mutations were seen though there may have been other unknown mutations.
Scientific, medical, legal, and ethical implications
- Though many of the ethical concerns are not new, they are now more urgent than ever as potentially greater impacts on humans and environment become more feasible.
- In January, 2015 scientists met to discuss these issues
- In March, 2015, scientists called for a worldwide moratorium on the use of this technology to alter human DNA and cause germ-line modification
- In April 2015, a statement came from the NIH Director: “NIH will not fund any use of gene-editing technologies in human embryos”.
- There may be challenges with CRISPR activity over time. Do-It-Yourself (DIY) CRISPR kits can be purchased-people can ‘do experiments with it in their garage’.