|Photo by: Autorecessive.svg: en:User:Cburnett via Wikimedia Commons|
Researchers have been using CRISPR for the past two months to edit DNA and genetic sequence.
Clustered regularly interspaced short palindromic repeats (CRISPR, /ˈkrɪspər/) are segments of prokaryotic DNA containing short, repetitive base sequences. These play a key role in a bacterial defense system, and form the basis of a genome editing technology known as CRISPR/Cas9 that allows permanent modification of genes within organisms. In a palindromic repeat, the sequence of nucleotides is the same in both directions. Each repetition is followed by short segments of spacer DNA from previous exposures to foreign DNA (e.g., a virus or plasmid). Small clusters of cas (CRISPR-associated system) genes are located next to CRISPR sequences.
Or another way to put it is CRISPR-Cas9 is a genome editing tool that’s able to “cut” DNA in a targeted fashion, allowing scientists to accurately edit the building blocks of life. You'll likely see it mentioned alongside the lesser known tandem of CRISPR-Cas1 and CRISPR-Cas2 – both of which splice "cut" pieces of DNA into a bacteria's own genome (more on that later).
A Harvard Medical school team earlier this month figured a way to GIF into the DNA of a living cell, splicing data from a short film into the genome of some E.Coli bacteria. The fallout from this could be extraordinary, and earth shattering. This can could turn DNA into something like organic storage devices and possibly completely eliminate genetic disease.
Originally discovered in the 1980’s Cas9 was found as a single-celled bacteria’s defense mechanism’s, this makes certain that cells have the ability to remove unwanted intruders. According to scientists if you adapt the technology, you are able to zero in on genome sequences with blistering speed and precision.
The holy grail for many scientists is finding a way to factually change DNA. So the possibilities of this are gigantic. CRISPR may be used to eliminate hereditary diseases such as sickle-cell anemia, Huntington’s and cystic fibrosis.
CRISPR-Cas9 can act like a sort of “find and replace” mechanism, like on a smart phone or computer document.
CRISPR is an acronym for the less catchy “clustered regularly interspaced short palindromic repeats”. The “Cas” part refers to “CRISPR associated.”
CRISPR, part of certain bacteria’s natural defenses, works its magic by detecting and incoming virus, copying it, blending segments of the unknown DNA to form its very own genome. Then it uses teamwork while Cas9 does the cutting, while Cas1 and Cas2 insert the exterior DNA into the cell's genome. Then when the virus is detected again CRISPR has an identical copy a cheat sheet so to speak of the genome sequence it needs to watch for. After it's spotted the Cas protein then swoops in slices and disarms the undesirable genes with pinpoint accuracy.
Carl Zimmer Yale Grad and popular science writer explains it this way “As the CRISPR region fills with virus DNA, it becomes a molecular most-wanted gallery, representing the enemies the microbe has encountered. The microbe can then use this viral DNA to turn Cas enzymes into precision-guided weapons. The microbe copies the genetic material in each spacer into an RNA molecule. Cas enzymes then take up one of the RNA molecules and cradle it. Together, the viral RNA and the Cas enzymes drift through the cell. If they encounter genetic material from a virus that matches the CRISPR RNA, the RNA latches on tightly. The Cas enzymes then chop the DNA in two, preventing the virus from replicating.”
Basically, CRISPR records the DNA sequences to destroy, and Cas 9 does the dirty work so to speak, like the hit-man.
CRISPR has so far only been used on humans in China. Embryos were received from a fertility clinic and scientists there attempted to use CRISPR-Cas9 for editing a gene that causes beta thalassemia in every cell. For the record, the embryos used in the experiment were “non-viable”, not able to give birth.
The results of the experiment were not good. One could say it failed miserably since 86 embryos were injected, 8 cells grew, 71 survived, and 51 were genetically tested 48 hours later. Jungiu Huang the lead researcher on that project told Nature “If you want to do it in normal embryos, you need to be close to 100%.” also saying “That’s why we stopped. We still think it’s too immature.”
The Chinese experiment caused quite a controversy as the New York Times explained: “The Chinese researchers point out that in their experiment gene editing almost certainly caused more extensive damage than they documented; they did not examine the entire genomes of the embryo cells.”
A different group of Chinese scientists became the first research group to use CRISPR-Cas9 on a human. The scientists injected a lung cancer sufferer with the patient's immune cells modified by CRISPR to disable the PD-1 protein, theoretically making the patient's body fight back against the cancer. However, results have yet to be reported.
The University of Pennsylvania will hold the first human trials in America later in the year, which will also involve cancerous genes.
|Photo by: Eric Ward via Wikimedia Commons|