The Latest Guide to Understanding CRISPR-Cas9

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The Latest Guide to Understanding CRISPR-Cas9
Giro Science | Shutterstock.com

The CRISPR Pill made headlines with its implications in the fight against Superbugs.

But CRISPR technology originated from research into gene splicing and genetic editing capabilities. Since DNA is the fundamental building block of existence, what CRISPR claims it can do is bold and a little terrifying.

What are the real-world applications and implications of this biotech?

Your Guide to Gene Editing 101Click To Tweet

What if Humans Had Complete Control Over Their Genes?

image of gene editing biotech from CRISPR and Cas-9 enzyme to potentially kill superbugs and enable genetic alterations with diseases and infections
YouTube | McGovern Institute for Brain Research at MIT

The above image comes from a YouTube video produced by the McGovern Institute for Brain Research at MIT from 2014. You can see that it involves gene splicing. One of the faculty members, Feng Zhang, led a team of researchers at MIT on the project, but many groups have looked into CRISPR-Cas9 biotech.

As early as 1993, researcher Francisco Mojica of the University of Alicante in Spain tinkered with CRISPR. Fun fact: the CRISPR DNA sequence and Cas-9 enzyme are a naturally occurring defense mechanism in various bacteria–most notably the kind that causes strep throat.

You Read Correctly–CRISPR is Strep Throat

Yes–we derived gene editing biotech from that pestering, cold weather (but also any time weather because it’s bacteria based) illness.

But don’t worry: the CRISPR-Cas9 strand operates similarly to bacteriophages.

It repeats a series of the same DNA sequences with unique sequences peppered in. These clusters became known as “clustered regularly interspaced short palindromic repeats.”

Though Ruud Jansen first used the term “CRISPR” in 2002, Mojica adopted the initialization throughout his research in discovering that CRISPR is basically an adaptive immune system.

This led others to tinker with the bacteria-based defense mechanism, as well. In 2005, Alexander Bolotin of the French National Institute for Agricultural Research discovered the unusual Cas-9 protein displaying nuclease activity. He specifically noted it in the Streptococcus thermophilus bacteria as opposed to other bacteria. Bolotin also discovered a PAM (protospacer adjacent motif) which allows for target recognition.

Genetic Editing Decades in the Making

image of David Tenant as Doctor Who explaining how time works for CRISPR and Cas-9 enzyme biotech article about fighting superbugs, diseases, and infections, as well as gene edits and genetic editing
David Tenant as Doctor Who | Giphy

From there, a plethora of scientists and researchers began to experiment with CRISPR and Cas-9 DNA sequences.

  • March 2006Eugene Koonin, US National Center for Biotechnology Information, NIH investigates spacer arrays and homologous phage DNA inserts
  • March 2007Philippe Horvath, Danisco France SAS attempts successful phage integration into CRISPR DNA in experiment with strep bacteria and yogurt production
  • August 2008John van der Oost, University of Wageningen, Netherlands makes headway regarding how CRISPR functions using crRNAs which guide Cas-9 proteins
  • December 2008Luciano Marraffini and Erik Sontheimer, Northwestern University, Illinois discovers that the target molecule is DNA instead of RNA
  • December 2010Sylvain Moineau, University of Laval, Quebec City, Canada found that CRISPR constructs double-stranded breaks at specific locations in target DNA AND that the Cas-9 protein is the only protein needed for cleavage
  • March 2011Emmanuelle Charpentier, Umea University, Sweden and University of Vienna, Austria discovers tracrRNA or trans-activating CRISPR RNA

    image of Tracer from Overwatch for article about CRISPR and Cas-9 enzyme biotech to fight superbugs, diseases, and infections, as well as allow for gene edits and genetic editing
    Tracer in Overwatch | Giphy
  • July 2011 Virginijus Siksnys, Vilnius University, Lithuania finds that CRISPR systems can totally function in other species heterologously (CRISPR units are self-contained)
  • January 2013 – Feng Zhang, Broad Institute of MIT and Harvard, McGovern Institute for Brain Research at MIT, Massachusetts harness the power of gene editing using CRISPR

Enough With the Timeline; Get to the Good Stuff!

Knowing how something came to be is all fine and good, but exactly how does CRISPR work? Simple: it acts similarly to how viruses do when they attack organisms – human or otherwise. Copies of the attacking virus’ DNA are made with temporary RNA. Then, these copies attach themselves to the attacked organism, forcing replication. This is how viruses infect things and it’s also how bacteriophages work, too.

image of how CRISPR and Cas-9 enzyme work to fight superbugs, diseases, and infections, as well as allow for gene edits and genetic editing
Dylan Roach | Business Insider

Since researchers can now harness the power of CRISPR-Cas9 (bacteria’s own natural defense system against infection) many believe they can utilize this against antibiotic resistant strains of bacteria.

How Does the Gene Splicing Function Work?

So, DNA has four amino-acid bases: adenine (A), thymine (T), guanine (G), and cytosine (C).

DNA will target any sequence acting a bit off to forego any potential damage. However, the CRISPR-Cas9 system operates differently since it can read 20 bases in any sequence. This elf-eyes-esque sight allows for better tailoring to a specific gene. There is even an online tool you can use to design a target sequence and how the RNA should interact with it.

image of chart on how CRISPR and Cas-9 enzyme biotech can attack superbugs, diseases, and infections beyond allowing for gene edits and genetic editing
SciVal | Elsevier

While the implications of this are monstrous, the real world applications do meet with a few stumbling blocks. One such block: the fact that the enzymes sometimes cut at the wrong place. Clearly, when it comes to gene editing, you want to be able to hit your mark every time.

A Brief History Leads to a Long Future

While the research into gene editing biotech has come a very long way, genetically engineered babies are still a bit further down the road–or are they? Researchers in Portland, Oregon successfully edited a human embryo in 2017.

However, this falls under the category of germline cells or reproductive cells. While the editing of somatic (or non-reproductive) cells is generally not controversial, editing reproductive cells raises several ethical dilemmas.

image of Transcriptic robotics lab using CRISPR-Cas9 enzyme biotech
Transcriptic

Despite this moral hang-up, use of CRISPR-Cas9 gene editing tech is already underway–even in robotics. Transcriptic’s robotic lab added this biotech to its list of services in 2015 in hopes to save time and money in the gene editing process. China instigated human trials in 2016, and we don’t even need to mention the implications regarding infectious diseases like Malaria.

We may have far to go with genetic editing and the fight against superbugs and viruses. But, we have taken very necessary and BIG first steps. 

TL;DR Fans, Here’s a Recap:

  • CRISPR/Cas-9 enables scientists to edit genomes and genes by removing, altering, or adding sequences to established DNA sections in organisms
  • The system is derived from naturally occurring defense systems in bacteria such as Streptococcus thermophilus
  • It works using RNA as the transportation and binding agent, supplanting old DNA sequences with your new, chosen sequence and Cas-9 enzyme as molecular scissors
  • DNA then recognizes the broken sequence and attempts to repair it
  • The CRISPR-Cas9 system works on almost any organism including animals and humans
  • Issues with mass real-world use include “off-target” effects where the Cas-9 enzyme cuts the wrong DNA sequence
  • Already an active practice with somatic cells
  • Huge implications in germline cell editing (a process illegal in many countries today)
image of molecular scissors CRISPR-Cas9 enzyme biotech
Genome Research Limited

With how far genetics has come in the last 30 years, we have to wonder how advancements in robotics and biotech will propel things even further.

What will be the biggest benefit if scientists can perfect CRISPR biotech: superbug eradication, somatic cell editing, or tackling the ethical implication of germline cell changes?

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