How Gene Editing Can Cure Sickle Cell Disease
Sickle cell is a terrible disease, that causes red blood cells to become deformed. This can lead to many problems, one being the blockage of blood flow. People may develop anemia, attacks of pain, swollen hands and feet, infections, and stroke. The worst thing about the disease, is that it is genetic. It is literally in your very DNA. But here is where CRISPR, a new gene editing technology, can save the day.
CRISPR? What’s that?
CRISPR is a technology that allows you to change the genes in your DNA. It is a protein which can find a specific part of your DNA and edit it, using RNA. RNA is a molecule which can read genetic information, and CRISPR uses a given RNA to find a specific part of DNA, and sends out an enzyme called Cas9, which is the enzyme that actually edits the gene.
You can disable it, which is the easiest thing to do, or fix a mistake in your genetic code or even replace a gene altogether, which is harder. Newer versions of CRISPR can even change a specific letter in your DNA. You can think of the original CRISPR as erasing a line in an essay and replacing it, and the new version as changing a specific part of that line.
This is what makes CRISPR so amazing. It is inexpensive, and easy to use as all you really need is the CRISPR protein and the guiding RNA molecule, and still gives you near complete control over your genome.
So how can we cure a genetic disease like sickle cell?
Luckily for us, we know the exact problem in a person’s genetic code that causes sickle cell disease. It can occur when a person inherits two abnormal copies of the hemoglobin-beta gene from each parent. Sickle cell anemia is recessive, so you can only get it if both parents have a copy.
To understand why this is, you must first understand dominant and recessive diseases. If a disease is recessive, then you can only get it if you inherit two copies of the gene causing it from your parents. If one parent didn’t have it, then it will not manifest.
However, you will still be carrying the gene that causes it, meaning you are still at risk at giving your child the disease. This is why two people without a recessive disease are still at risk of giving their child the disease if they both still carry the gene.
If the disease is dominant, then your child will have a 50% chance of getting the disease no matter what. The reason is because you get one chromosome from each parent. If one of your parents has a dominant disease, and you inherit the chromosome that carries the bad gene, you’ll get the disease, but if you are lucky and got the other chromosome that didn’t carry the bad gene, you won’t have the disease.
If that was confusing, these charts may help you understand it. This is a chart that shows how a recessive situation may play out:
And a chart that shows how a dominant disease situation could play out:
Again, it still may be confusing, but just know that a recessive genetic disease only manifests if both parents carry the gene, and a dominant one manifests 50% of the time.
Anyways, with CRISPR, we can give it a guide RNA to navigate to the sickle cell gene and edit it, and boom! No more sickle cell disease! Simple enough.
Sounds awesome! Let’s do it!
Woah, woah. Not so fast. The thing is, we can’t just jump to trials on humans. We simply don’t understand enough about our genes. We have sequenced and acquired the entire human genome, but the sad truth is that we barely understand what most genes even do. We can’t edit genes willy nilly, because we could ruin something essential for us to survive.
Some genes have multiple uses. A person with a sickle cell affected gene is actually more resistant to malaria. This is pretty crazy, and in this case the trade-off is negligible, since sickle cell causes a lot of pain but you are unlikely to get malaria in a first world country. But what if a gene that causes a painful disease also gives you a longer lifespan. There is simply too much we don’t know.
But we are making progress. Scientists around the world are learning more about what our genes do every single day. And hopefully, a few decades from now, we can cure not just sickle cell disease, but all other genetic diseases as well.