CRISPR: The new tool in the gene editing revolution explained
ABC Science
ByBernie Hobbs
A powerful new gene-editing technology called CRISPR has enormous potential to treat human diseases but the ability to tinker with genes can also be controversial. Here we explain what CRISPR is and how it works.
Key points:
- CRISPR is a faster, cheaper and more accurate way of editing genes
- It should allow replacing faulty genes with healthy ones
- CRISPR is not yet accurate enough to use on people
- Scientists have called for a moratorium on using CRISPR on sperm and egg cells
But that's nothing compared to the genetic revolution that we're at the beginning of right now, thanks to a technique adapted from bacteria called CRISPR (the catchy acronym for clustered regularly interspaced short palindromic repeats).
Researchers learn what genes do by switching them on or off, or cutting them out of the DNA in a cell entirely.
Since it appeared in 2012, CRISPR has completely transformed the process that researchers use to edit genes this way.
It's not the first method devised for this kind of genome editing, but CRISPR is a lot cheaper, faster, and more accurate than any of the alternatives. In technology jargon, it's a capital D disruptor.
And with applications in gene therapy (replacing faulty genes with healthy ones), drug research and agriculture for starters it's no wonder the method has taken off like a rocket.
What is CRISPR? And how does it work?
Editing genes can mean removing or replacing an existing gene, switching a gene on or off, or inserting a new gene altogether.
Whatever the aim, the first step is always to find the stretch of DNA that codes for the gene and grab hold of it, so a cut or tweak can be made.
CRISPR not only finds the target gene and locks on, it also delivers an enzyme that cuts the DNA. And it does all this with unprecedented accuracy.
The reason it's able to manage this precision double act is because CRISPR is made of ribonucleic acid (RNA) — a molecule that can be tailor-made to perfectly match a sequence of DNA or to bind to a protein.
CRISPR RNA does both jobs — one end is custom-made to match the target gene's DNA sequence, and the other end binds to a DNA-cutting enzyme, or nuclease.
It's a brilliant system, and it wasn't cooked up in a lab — scientists pinched it from bacteria.
Simple beings that they are, bacteria have a version of an immune system, and CRISPR is at the heart of it.
When a virus invades a bacterial cell, it leaves traces of its DNA in the bacterial genome. If the bacterium encounters that virus again, CRISPR RNA uses the viral DNA remnants and a nuclease called Cas9 to attack the virus.
An improved version of this CRISPR-Cas9 combination is now being used in laboratories around the world.
Cas9 is not the only nuclease in the game — there are a number of Cas (CRISPR-associated) proteins, each with a slightly different capability.
Researchers simply order the sequence of guide RNA to include a part of the gene they're interested in, plus the Cas binding sequence, mix it with the Cas protein to suit the job and they're ready to go.
Why is CRISPR controversial?
As with all methods that let us directly change genes, CRISPR has raised alarm bells on a few fronts. And its rapid uptake across the board in biotech research has some scientists understandably concerned that we're racing ahead with experiments before knowing the full implications of the technology.
Nowhere is this more evident than in work involving human embryos.
The announcement in 2015 thatChinese scientists had edited the genome of an embryodrew global attention to the issue. (The embryo was unviable — physically incapable of developing into a fetus or human.)
In 2016 approval was also given to aBritish biologist to use CRISPR on unwanted human embryosto better understand the role of genes in healthy development. (The researchers will use unwanted IVF embryos and the experiments — and embryos — will be terminated after one week.)
While the embryos from these experiments won't result in a child, they have added urgency to the debate around what limitations need to be put on the use of CRISPR.
That was the focus of the International Summit on Human Gene Editing in Washington in December 2016, which resulted in a call for a moratorium on using CRISPR on germ line cells (egg and sperm) until all safety issues and societal concerns have been addressed. This call has since been backed bya second group of researchers who attempted to edit human embryos.
As the accuracy and safety of CRISPR improves, and the potential clinical benefits of CRISPR become feasible, this stance will certainly evolve.
Questions:
- What is CRISPR? Do your best to describe it from the reading.
- How is this similar to the test tube baby article?
- How is it different?
- What is your opinion? Is this a great new scientific breakthrough? Is this something that requires extreme caution? Or is this something that should be avoided all together? EXPLAIN!!!!!!!