Will CRISPR let us cure genetic diseases?

Do genetics hold the missing puzzle piece to cure all diseases that other methods can't?
16 November 2021


Green coronavirus particles around a strand of DNA.



Vaccines only work for infectious diseases, not for genetic diseases like cystic fibrosis. So from a genetics point of view, will we be able to eradicate genetic diseases as well in the future?


Sally Le Page asked molecular biologist and Royal Society Entrepreneur in Residence at Oxford, Nessa Carey, about if we can cure genetic diseases through the study of genetics.

Nessa - In theory? Yes, some of them. In reality? Probably no, just because it would be very difficult to do. But we have this amazing technique now called CRISPR, which is basically a way of changing DNA. Every human inherits 3000 million letters of DNA information from their mum and 3000 million from their dad, so you get 3 billion of each. Sometimes just one of those might be wrong, one out of 3 billion can give you a really devastating genetic disease. Sometimes it's a bit more than that, so in cystic fibrosis that John mentioned it's three letters typically cause the most common form of cystic fibrosis. And it used to be, you could do nothing about it. But now this technique of CRISPR is this amazing way of changing DNA information incredibly precisely and incredibly sensitively and very, very effectively. And we're starting to use that to treat diseases.

Sally - How could we do that though? Because I've got millions or billions of cells in me and you'd have to change the DNA in every single cell. Right?

Nessa - Well, there's two ways of doing it. You have far more cells than that. You have 70 trillion.

Sally - I feel very good about myself now.

Nessa - If you counted them at one cell a second, it would take you one and a half million years. It's an incredible number of cells. If you look at the disease that we're closest to treating right now using this technique, it's sickle cell disease which is a disease of the red blood cells. To treat that, you don't have to treat every cell in the body, because most of the cells in the body are absolutely fine with sickle cell diseases. Only the ones that are in the red blood cells. So what companies are doing, because this is all being done by drug companies, is they take bone marrow out of somebody with sickle cell disease.

Sally - Because bone marrow is what produces the red blood cells.

Nessa - That produces the red blood cells. They use CRISPR to correct the genetic defect in the bone marrow. Then you inject that bone marrow back into the original patient and it starts producing normal red blood cells. So you can actually cure sickle cell disease rather than just treating it, which is just astonishing.

Sally - Does that mean that there are people walking around that we have genetically altered already?

Nessa - Yes there are, and the initial results are amazing. You have people who used to have to go to hospital for transfusions every month, who were in massive pain every month, now haven't been in hospital for over a year. Now the thing is though, there you're treating and then probably curing the individual, but if they have kids, they still have a 50% chance of passing on that defective gene to their children. We do in theory have the option of actually wiping out a genetic disease in a particular family. Which would be basically an egg and a sperm fuse and they formed the zygote, which is that single cell from which all these 70 trillion others were eventually derived you can use this technique, in theory, in that zygote. You'd have to do this in the test tube environment, so it's test tube baby technology. Then if you correct the genetic mutation and you implant that zygote back into the mother, every cell that comes from that original zygote, all 70 trillion of them, they will all have been corrected and you will have stopped that mutation and that disease in that family. Now that's going to be amazingly expensive and there's lots of ethical issues. You're not allowed to do it at the moment.

Sally - But we have the technology to do it.

Nessa - We have the technology to do it. We know that this works in other animal species. We will see a big change.


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