CRISPR facts: from bacterial defense to gene editing

CRISPR facts start with a bacterial defense system that ended up changing gene editing. What began as a way for microbes to remember past infections became one of biotechnology’s most important tools.

What is CRISPR?

CRISPR is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. Each CRISPR sequence comes from a DNA fragment of a bacteriophage that had previously infected the prokaryote or one of its ancestors.

Those sequences help detect and destroy DNA from similar bacteriophages during later infections. In that way, CRISPR provides a form of heritable, acquired immunity in prokaryotes.

CRISPR is widespread in microbial genomes. It is found in approximately 50% of sequenced bacterial genomes and nearly 90% of sequenced archaea.

How did scientists realize CRISPR was an immune system?

The first experimental evidence that CRISPR was part of the adaptive immune system was published in 2007. That result helped shift CRISPR from an odd genetic pattern to a clear biological defense mechanism.

In 2012, Jinek et al. fused crRNA and tracrRNA into a single-guide RNA, simplifying Cas9 targeting. That step made the system easier to direct at a chosen DNA sequence.

CRISPR gene editing is based on a simplified version of the bacterial CRISPR-Cas9 antiviral defense system. By delivering the Cas9 nuclease complexed with a synthetic guide RNA into a cell, the cell’s genome can be cut at a desired location.

How did CRISPR become a gene-editing tool?

In 2013, Cong et al. and Mali et al. applied CRISPR-Cas9 to edit human cell cultures. Those experiments showed that the system could be turned into a practical editing method for human cells.

The technique is considered highly significant in biotechnology and medicine because it enables in vivo genome editing and is exceptionally precise, cost-effective, and efficient. CRISPR-Cas9 is a technology that can be used to edit genes within living organisms.

The Nobel Prize in Chemistry recognized the development of the CRISPR-Cas9 genome editing technique in 2020. That award marked the scientific importance of the method after its rapid rise from basic biology to a usable tool.

What happened in 2023 with CRISPR-based treatments?

In 2023, the first drug making use of CRISPR gene editing, Exagamglogene autotemcel, sold under the brand name Casgevy, was officially approved for use in the United Kingdom.

On 2 December 2023, the Kingdom of Bahrain became the second country in the world to approve the use of Casgevy. In December 2023, the FDA approved the first gene therapy in the United States to treat patients with sickle cell disease.

Those approvals placed CRISPR in medicine as well as in the laboratory, with gene editing moving into officially approved treatments.

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