What Is CRISPR and Why Is Everyone Excited About It?

25 de marzo de 2020

3 min de lectura

What is CRISPR?

While the term CRISPR sounds like it's associated with a head of lettuce, more and more people recognize the acronym as a buzz word floating around the biomedical community. So what does it mean? The words of the acronym themselves are not very helpful (Clustered Regularly Interspaced Short Palindromic Repeats), which actually describe a natural process that bacteria use to fight off viral infection. The CRISPR process is the equivalent of an immune system for a single-celled organism, allowing individual bacteria the ability to remember virus types it has encountered before.

While this was an interesting finding coming out of basic science research, the real excitement lies with adopting the CRISPR process to edit DNA in any type of cell. This tool (termed CRISPR-Cas9, where Cas9 is the enzyme driving the DNA change), was discovered in 2012 by Jennifer Doudna and Emmanuelle Charpentier. In their groundbreaking study, they showed that the CRISPR-Cas9 tool could be targeted to cut any piece of DNA with high precision with the inclusion of a guide RNA piece to direct the complex. Subsequent studies have also demonstrated that CRISPR-Cas9 can be used to insert DNA pieces into a gene. This means that we now have the ability to permanently change the underlying genetic sequence of a cell - and that is really powerful.

Jennifer Doudna gave a TED Talk in 2015 explaining CRISPR-Cas9 and the implications for the biology and medical fields. Importantly, genetic changes using CRISPR-Cas9 only happen in one cell at a time. One of the limits of the technology currently is you could never, say, change the DNA of every cell in an adult human. The tool is limited for use on a small number of cells, like cells growing in a lab petri dish. Nevertheless, the technology has come an amazing distance in a few short years, being widely adapted as a tool in research labs around the world to speed our understanding of different genes, to engineer malaria resistant mosquitoes, and to make precise modifications in plant species.

Isn't using CRISPR on humans unethical?

Because of the potential to substantially modify a person's DNA, CRISPR medical technology in humans has moved forward cautiously and with heavy ethical considerations in the United States. CRISPR use on human embryos, a much easier target because early embryo stages only contain a few hundred cells, is the biggest area of concern. Termed human germline gene editing (GGE), the ethical argument was abstract until 2018 when a Chinese researcher announced at a conference that he had CRISPR engineered two HIV-resistant embryos that we subsequently implanted and birthed as outwardly healthy children. The world was outraged at his unethical behavior (and he didn't even do it well, as one of the embryos still contained the gene he was trying to remove) and He Jianku and his colleagues were fined and sentenced to prison.

While He Jianku's example serves as a warning for researchers thinking about going rogue, there is still interest in using CRISPR to cure untreatable genetic conditions, like cystic fibrosis and Huntington's Disease. With ethical regulatory oversight and transparency of its use, there is hope that CRISPR technology can be used to end the passage of genetically inherited diseases.

Are any CRISPR therapies available now?

While GGE CRISPR technology is off limits, other uses for CRISPR that only target a small group of cells in adults and children are making its way into treatment sectors. Since these are only changing the genetic sequence of a few cells of the body, ethical concerns are minimal. Clinicaltrials.gov currently lists over twenty CRISPR studies, with more planned in coming years. One of the first clinical trials has started using CRISPR to reprogram immune cells to fight cancer. While initials trial results did not produce drastic results, every test result is being used to hone clinical adaptations of this new biotechnology.

Another CRISPR clinical trial went underway in early 2020 to treat a rare genetic blindness called Leber congenital amaurosis. The approach uses surgery to insert CRISPR-Cas9 enzyme and genetic material for targeting and editing directly into the eyeball. The hope is that these materials work their way into enough cells of the eye to repair the disfunctioning gene for that patient, restoring vision.

As more uses for CRISPR-Cas 9 technology are being imagined and developed every day, expect to hear more exciting news on the genetic engineering front in the future.

Source

www.ncbi.nlm.nih.gov/pmc/articles/PMC6286148/

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What is CRISPR?

Isn't using CRISPR on humans unethical?

Are any CRISPR therapies available now?

Source

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