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     So what’s all the rage with Clustered Regularly Interspersed Palindromic Repeats A.K.A ‘CRISPR’? Well for starters it cured a man from HIV (the first ever cure for HIV), but it has also opened up innumerable possibilities for both industry, therapeutic use and research.

What is CRISPR?

    Screen Shot 2017-08-21 at 10.27.58 AMCRISPR’s are regions in a bacteria’s genome that play an essential part in that bacteria’s immune system through a process known as adaptive immunity. Discovered in the 1980s, the genetic repeats were a puzzle to biologists until, in 2007, a certain Rodolphe Barrangou and his colleagues figured out the purpose of the strange DNA repeats. While working for Danisco, a food production company (bought out by DuPont in 2011), the researchers were doing genetic sequencing work on the bacteria Streptococcus Thermophilus.2 This bacteria is an essential ingredient in yoghurt and cheese production but was constantly being infected by bacteriophages that were costing the dairy industry billions of dollars. Eventually Barrangou and his team figured out the link between the CRISPR and the bacteria’s immune defense and, according to Barrangou’s words, it was “an eye-opening moment when we first thought of the link between CRISPR sequencing content and phage resistance”.2 What they learned was that the CRISPR sequences are repeats in certain loci in the chromosome called the CRISPR  loci) where copied viral DNA is stored. This copied genetic information allows the bacteria to identify future attacks from the same virus and interfere, thus protecting itself. So CRISPR DNA is really a ‘genetic memory’ for the immune system of a bacteria.3

 

 

How does the immune defense mechanism of CRISPR work?

Screen Shot 2017-08-21 at 10.34.58 AM     In this system, when a virus invades a bacteria it’s viral DNA is copied and incorporated into the bacteria’s own genetic code. This DNA sequence, which is an exact copy of the virus’, is transcribed (transcription is the production of RNA from a DNA blueprint) into CRISPR RNA. The CRISPR RNA (specifically, crRNA) then complexes with an enzyme called Cas9 endonuclease, which will be responsible for cutting up and destroying the viral DNA. The crRNA guides the nuclease enzyme to its complementary genetic sequence on the viral DNA and, using another segment of RNA (tracrRNA) for cleavage of the DNA, destroys the viral DNA. This process can be separated into 3 stages: Adaptation, CRISPR RNA transcription, and interference.3

     Hence, therein lies the appeal of CRISPR gene editing technology. It is far more simple than most gene editing technologies used today, making it a better candidate for single point mutations (insertions and deletions of genes).4

 

Uses of CRISPR gene editing

  1. Industry:

     CRISPR gene editing is already being used in the food industry to maximize profits and minimize wastage. For instance, the Roslin Institute in Scotland conducted a research project on using the editing technology to make pigs resistant to Porcine Reproductive and Respiratory Syndrome (PRRS). This disease costs the swine industry approximately €1.5 billion each year, a major sum that could now be reduced greatly. It was discovered that a certain molecule on the macrophage cells of the pig was responsible for interacting with the virus and causing infection. Therefore, by removing the gene responsible for this molecule they the study found that infection was averted. This advancement is one of many facilitated by CRISPR technology (the above example of Danisco is another example).5

2. Research:

     The amount of research that can now be conducted on gene specificity thanks to CRISPR technology is vast. The University of Rochester’s center for RNA Biology are using the technology to slow the growth of cancer cells. This oncological project is using CRISPR to remove a protein known as Tudor-SN. Tudor-SN plays a key-role in the early phases of the cell cycle, the cycle that is turbo-boosted during the uncontrolled cell growth characteristic of cancer. By removing this protein research has shown that cancerous cells take much longer to reproduce and therefore the development of the cancer in a patient is slowed, allowing for more time during treatment.6

3. Therapeutics:

     Timothy Ray Brown was an HIV-positive patient but thanks to the CRISPR gene editing of stem cells he was given a white blood cell transplant with HIV resistant white blood cells. Some people are born with a mutation that makes them resistant to HIV, thus if their blood cells are transplanted, theoretically, other HIV patients should be cured. The problem arising with this is that it is very rare to find a transplant match who will minimize the risk of rejection and who also has the mutation.8 Therefore, the application of CRISPR into this treatment became a necessity as the technology allows scientists to edit pluripotent stem cells, giving them the HIV-resistant mutation, before they are specialized into white blood cells and transplanted into a patient. This process worked for Mr. Brown who is very lucky to no longer need anti-retroviral medications.7

     The applications of CRISPR gene editing are truly endless and the research using the technology will reveal exciting discoveries year after year. Of course, like any other new technology, the CRISPR editing still needs some refinement to mitigate the off-site genomic targeting that sometimes occurs with it.

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[1] Chan, Keith. Gene Loci and Alleles.png. Digital image. Https://commons.wikimedia.org/wiki/. Wikimedia, 24 July 2015. Web. 12 June 2017.

[2] Grens, Kerry. “There’s CRISPR in Your Yogurt.” Scientist Jan. 2015: n. pag. The Scientist. LabX Media Group, 1 Jan. 2015. Web. 12 June 2017.

[3] Pak, Ekaterina. “CRISPR: A game-changing genetic engineering technique.” Web log post. Http://sitn.hms.harvard.edu. Harvard University Graduate School of Arts and Sciences, 31 July 2014. Web. 12 June 2017.

[4] Reis, Alex, Ph.D., Breton Hornblower, Ph.D., Brett Robb, Ph.D., and George Tzertzinis, Ph.D. “CRISPR/Cas9 and Targeted Genome Editing: A New Era in Molecular Biology.” NEB expressions 1 (2014): n. pag. Web. 12 June 2017.

[5] Middleton, Jen. “Gene-edited pigs show signs of resistance to major viral disease.” The Roslin Institute (University of Edinburgh) – News. University of Edinburgh, 24 Feb. 2017. Web. 11 June 2017.

[6] Weintraub, Arlene. “Using CRISPR gene editing to slow cancer growth.” FierceBiotech. Questex LLC., 25 May 2017. Web. 11 June 2017.

[7] Schafer, Jamie. “The man who was cured of HIV.” Science in the News. Harvard University Graduate School of Arts and Sciences, 15 May 2011. Web. 11 June 2017.

[8] Iniss, Mara. “Gene Editing Technique Allows for HIV Resistance?” Science in the News. Harvard University Graduate School of Arts and Sciences, 13 June 2014. Web. 11 June 2017.