CRISPR is a world changing technology that is essentially used to edit genes. The discovery of CRISPR took place in the University of Alicante, Spain. Reported in 1993, Francisco Mojica was the first to characterize CRISPR locus. Throughout the 90s and early 2000s, Mojica realized that what was once reported as unique sets of repeat sequences actually shared common features, which are known to be hallmarks of CRISPR sequences. Through this finding, Mojica was able to correctly hypothesize that CRISPR is an adaptive immune system. In the year 2013, Feng Zhang, was the first scientist to successfully adapt CRISPR-Cas9 for genome editing in Eukaryotic Cells. Zhang was able to engineer two different Cas9 orthologs and he then demonstrated targeted genome cleavage in both human and mouse cells. They discovered that this system could then be used to target multiple genomic loci and could also drive homology directed repair.
How Does it Work?
“Clustered regularly interspaced short palindromic repeats,” also known as CRISPR, are repeats found in bacteria’s DNA. CRISPR-Cas9 was adapted by scientists from a naturally occurring genome editing system in bacteria. This bacteria captures parts of DNA from invading viruses and it uses them to create DNA segments known as CRISPR arrays. This DNA allows the bacteria to recognize and remember the virus’s. If the same virus, or a similar one, attacks again, the bacteria will consequently RNA segments in order to target the viruses DNA. After, the bacteria uses the enzyme Cas9 in order to cut the DNA apart, thus disabling the virus. Scientists in a lab will create small pieces of RNA that attach to a specific target sequence of DNA and also the Cas9 enzyme. In this process, the RNA is used to recognize DNA and the Cas9 will cut the targeted DNA. Once cut, researchers will utilize the cell’s ability to repair DNA in order to add or remove pieces of genetic material. It can also replace existing DNA with custom DNA in order to make changes.
How is it used?
CRISPR is a tool that can be used to fight cancer among other known diseases. The therapy involves making four modifications to T-cells. T-cells are cells that help fight cancer. CRISPR adds a synthetic gene that gives the T-cells a claw-like receptor. This receptor can locate NY-ESO-1 molecules on cancer cells. CRISPR is then used to remove three genes. Two of the removed genes can interfere with the NY-ESO-1 receptor and the third limits a cell’s cancer killing abilities.
Another way CRISPR is used is against Leber’s Congenital Amaurosis(LCA). LCA is a family of congenital retinal dystrophies that results in vision loss. Patients tend to show nystagmus, sluggish pupillary responses, decreased visual acuity and photophobia. The CRISPR trial focuses on one gene mutation that causes a severe form of degeneration. It is said that this mutation creates somewhat of a “stop sign,” and RNAs will target sequences on either part of the stop sign. The Cas9 enzyme will then cut them out, allowing the DNA to then repair itself.