CRISPR gene editing
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| CRISPR gene editing | |
|---|---|
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| Name | CRISPR gene editing |
| Inventor | Emmanuelle Charpentier, Jennifer Doudna |
| Institution | University of California, Berkeley, Max Planck Institute |
| Year | 2012 |
CRISPR gene editing is a powerful technology derived from a natural bacterial immune system that allows for precise modification of DNA within living organisms. The system's core components are a guide RNA molecule and a Cas9 enzyme, which together can be programmed to target specific genetic sequences. This programmability has revolutionized genetic engineering, enabling applications from basic research to potential therapies for genetic disorders. The foundational work on this system earned Emmanuelle Charpentier and Jennifer Doudna the Nobel Prize in Chemistry in 2020.
Overview
The technology is adapted from the CRISPR-Cas immune defense found in bacteria and archaea, which records snippets of viral DNA to fight future infections. Researchers including Feng Zhang at the Broad Institute and George Church at Harvard University were instrumental in demonstrating its function in eukaryotic cells. Its simplicity and efficiency compared to earlier tools like zinc finger nucleases and TALENs have made it a ubiquitous tool in molecular biology laboratories worldwide. The ability to easily design guide RNA sequences has democratized access to precise genome manipulation.
Mechanism of action
The process begins with the design of a single guide RNA that is complementary to a target DNA sequence within the genome. This RNA forms a complex with the Cas9 nuclease, most commonly derived from Streptococcus pyogenes. The complex scans the genome until it locates a match adjacent to a short protospacer adjacent motif. Upon binding, Cas9 creates a precise double-strand break in the DNA helix. The cell's natural repair machinery, primarily non-homologous end joining or homology-directed repair, then fixes the break, often introducing targeted changes or insertions.
Applications
In biomedical research, the technology is used to create animal models of human diseases in organisms like mice and zebrafish for studies at institutions like the Jackson Laboratory. Agricultural applications include engineering crops for improved yield, drought resistance, or nutritional content, with companies like Bayer and Syngenta investing heavily. Clinical trials are underway for treating conditions such as sickle cell disease, beta-thalassemia, and Leber congenital amaurosis, led by firms like CRISPR Therapeutics and Editas Medicine. It also holds promise for strategies like gene drive to control vector-borne diseases such as malaria.
Ethical and safety considerations
A major controversy arose following the 2018 announcement by He Jiankui of the first gene-edited babies, which was widely condemned by the international scientific community and led to his prosecution under Chinese law. Concerns about off-target effects and unintended mutations drive ongoing research to improve specificity, supported by organizations like the National Institutes of Health. The potential for germline editing raises profound questions about heritability and human enhancement, debated in forums like the International Summit on Human Gene Editing. Regulatory bodies, including the U.S. Food and Drug Administration and the European Medicines Agency, are developing frameworks to govern clinical use.
History and development
The foundational discovery of clustered repeats in bacterial DNA was made by Yoshizumi Ishino and colleagues in 1987. The function of these sequences as an adaptive immune system was elucidated later by researchers like Philippe Horvath at Danisco and Rodolphe Barrangou. The pivotal adaptation into a programmable editing tool was published in 2012 by the teams of Emmanuelle Charpentier and Jennifer Doudna in the journal Science. Subsequent patent disputes, notably between the Broad Institute and the University of California, Berkeley, have shaped the commercial landscape. The field continues to advance with the discovery of novel enzymes like Cas12 and Cas13 for different applications.