How to make pigs fly

No, you did not hear me wrong. We are between 10 and 20 years away from having the capacity to breed pigs with wings. What I am talking about here is genetic engineering. Let’s get that out of the way. This is genetic engineering on a scale that is comparable to that seen in films. The super-dinosaur in Jurassic world? That’s the level we’re talking about. What this is is a technology called CRISPR. That stands for clustered regularly interspaced short palindromic repeats (thanks Wikipedia). Which isn’t the snappiest of names. But the technology (or rather, biotechnology) behind it is anything but.

CRISPR has the potential to be a cheap, effective, universally applicable and safe genetic engineering technique that works for…everything. Now I’ve done enough clickbait-y opening, I will explain what CRISPR actually is. CRISPR is actually not an artificial mechanism. It’s a system found inside bacteria cells, designed to protect against viruses. When inside a cell, it doesn’t look like the future of genetics. It looks like this.

PDB 1wj9 EBI.jpg

But what does it meeaan???

It turns out that in lots of bacterial DNA, there are these weird repeating patterns. Five of them, with weird chunks in between. Sort of like:

abcd skjdfh abcd isudgh abcd osfgjo abcd sdhfjf abcd

Now this is really unusal for DNA. So around 2005, some biologists were playing around with a DNA database and decided to try to search for those blips. And they found something. Turns out, for hundreds of millions of years, bacteria have been splicing little bits of viral RNA (which viruses have instead of DNA but is very similar) into their own DNA. And after a few more years of research, they found out why. What follows is a description of what happens when a bacteria is invaded by a virus, and how CRISPR comes into that.

When a virus invades a bacterium cell, it basically explodes. It sprays RNA all over the shop, which then goes to find enzymes that allow the virus to reproduce. The bacteria then responds by activating an antibody system. This basically goes out into the cell and starts strafing any RNA it can find, regardless of whether it is viral or not. This is a lot like US ground troops in the Middle East. And also like US ground troops, they aren’t terribly effective. The majority of times, the bacterium will become overwhelmed with viruses and the cell dies.

But occasionally, the bacterium will win. And then, it wants to protect itself and any future generations against viral attack. So rather than destroying all the virus RNA, it keeps some. It stashes it in the only place that it will survive. It transplants that viral RNA into its own DNA. Then, if that bacterium (or one of its ancestors) is attacked by that virus again, it doesn’t deploy the ground troops. It goes to that viral RNA data and builds a different enzyme. That enzyme is CRISPR. PDB 1wj9 EBI.jpg Every CRISPR enzyme has the viral RNA code built into it. It goes out and searches the entire cell for anything that matches the RNA code. If it doesn’t find it, it will move on. If it does find that RNA, it will encircle it and tear its head off. Then after a few days, the enzyme will self destruct.

So what CRISPR is, in effect, is a really efficient way to search for and destroy very specific pieces of DNA. Which, when you want to go through the genome of an embryo and replace certain parts of the DNA with others. So genetic engineering. CRISPR is a way to do really cheap, really effective genetic engineering. I’ll give you an example.

Huntington’s Disease is a genetic disorder caused by a slight mutation on the HTT gene. In the vast majority of cases, one side of the chromosome containing the HTT gene is fine but the other side is damaged. (You actually have two copies of your DNA in every cell, with each chromosome containing two copies of the same DNA.) But that half is enough to mess with the cell. Let’s say we program CRISPR to find the damaged DNA. This is a fairly easy process, that only takes a few days in the lab. Then we inject CRISPR into the cell and let it run. It goes and finds that DNA with remarkable efficiency and accuracy, and tears it to shreds. At this point, another enzyme in the cell will recognise the damage and send in a repair enzyme. This grabs a copy of the undamaged, correct DNA from the other half of the chromosome and sticks it into the gap. And that cell has been cured of Huntington’s disease.

Now say you do that in an IVF embryo. If both parents have some of the Huntington’s gene but neither has enough to develop the disease, there is a fairly high chance that the baby will develop the disease at some point. So, when the baby is only a few cells, why not just…snip out the Huntington’s gene?

What I just described has been done in a massive variety of animals – dozens of mammals, insects, fish – with varying degrees of success. But never yet on humans. Until…

Capture

Last month, a Chinese team used CRISPR to try to alter the genome of embryos that had been rejected for IVF implantation. This made global news, as doctors worldwide spoke up against the vast ethical breach that this kind of experiment is. But just as loudly, other doctors were saying things like:

Capture1

Remember, this isn’t Jurassic Park. This is the possibility of a future with out disease like cystic fibrosis, they said.

Personally, I am in the latter camp. If we were to CRISPR all IVF babies in the UK so they didn’t have cystic fibrosis, that would save hundreds of lives every year. Which in my book, is worth it. But we must keep this as a medical field. It is far too easy to stray towards the dark realm of designer babies. That is a future that we cannot allow to happen.

We are now at the crossroads. Within 20 years we could have the technology to safely and easily eliminate genetic diseases. We can allow that to happen, and risk a future of designer babies. Or we could ban it outright, and keep struggling under the mantle of this diseases. What would you do?

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