CRISPR gene editing technique

The use of the CRISPR gene editing technique on human embryos used in research has been given approval for the first time by authorities in the UK.

In the late 1980s and mid-1990s, genomes of diverse lineages of bacteria and archaea (the latter representing a domain of single-celled prokaryotic microorganisms) revealed clusters of regularly interspaced short palindromic repeats, known today under the abbreviation CRISPR.

Later it was found that these repeat sequences (previously considered disparate) share a common set of features. In 2005, a link between CRISPR arrays and protection of the host against invading genetic elements has been established, which boosted a myriad of genetic and biochemical studies exploring the intricate details of this complex genetic barrier.

This in turn led to the discovery of CRISPR-associated (Cas) proteins, which are (alongside repeats, spacers and partially conserved leader regions) essential functional components of this astonishing type of adaptive immune system.

Today, CRISPR/Cas9 is successfully adapted for genome editing of various organisms, offering a revolutionary technique for researchers around the world. It offers a number of advantages over other genome editing approaches (such as transcription activator-like effectors and zinc fingers), thus writes Dr Tomislav Meštrović in an article at http://www.news-medical.net.

CRISPRs were first discovered in archaea (and later in bacteria), by Francisco Mojica, a scientists at the University of Alicante in Spain. He proposed that CRISPRs serve as part of the bacterial immune system, defending against invading viruses.

Mojica’s theory was experimentally demonstrated in 2007 by a team of scientists led by Philippe Horvath. In January 2013, Feng Zhang at the Broad Institute and MIT published the first method to engineer CRISPR to edit the genome in mouse and human cells.

How does the system work? www.broadinstitute.org explains that CRISPR “spacer” sequences are transcribed into short RNA sequences (“CRISPR RNAs” or “crRNA”) capable of guiding the system to matching sequences of DNA.

When the target DNA is found, Cas9 – one of the enzymes produced by the CRISPR system – binds to the DNA and cuts it, shutting the targeted gene off. Using modified versions of Cas9, researchers can activate gene expression instead of cutting the DNA.

These techniques allow researchers to study the gene’s function. Research also suggests that CRISPR-Cas9 can be used to target and modify “typos” in the three-billion-letter sequence of the human genome in an effort to treat genetic disease.