Gene Editing, Part II: It’s Freaking Insane

Three words: genetically modified human. Yea, this is happening.

How is this even possible?

Last time we talked about proofreading an essay as a metaphor for editing DNA. One type of molecular “cursor” that can be placed at a particular genomic location to edit it is called a zinc finger nuclease (ZFN). It’s an engineered protein originally reported by Johns Hopkins researchers in 1996, but recently perfected by Sangamo Biosciences. It has a DNA-binding domain that recognizes a certain unique stretch of DNA (Hockemeyer et al., 2009). When it finds the right genomic location, the ZFN breaks the DNA. At this point, there are three options: the gene can be disrupted so it doesn’t work anymore (if the gene is harmful), an incorrect DNA segment can be replaced with a correct one, or a whole gene can be inserted. (If you’re curious about the molecular specifs, read more here.)

There are a couple other “cursors,” called TALEN and CRISPR. If you’re interested in further reading, I’d highly recommend this article by Gaj et al., 2013, which compares the different methods and describes which have been used to treat which diseases. The newest technique, called the CRISPR/Cas9 system, is so far the easiest of these methods–unlike the other two, it uses an RNA sequence to recognize the exact target site–but it isn’t yet as accurate.

What has it already been used for?

This article reports that clinical trials are currently underway to treat a retinitis pigmentosa, a genetic diseases that causes blindness. The treatment involves taking a blind patient’s skin cells, turning them into iPS cells (induced pluripotent stem cells), and injecting them into the retina of a diseased patient’s eye to grow a new, healthy retina.

In 2013, ZFN technology was used to give Jameson Golliday a working IL-2 gene, which encodes an essential immune system signaling molecule. Jameson was born with X-linked SCID, or Bubble Boy disease–essentially, his immune system didn’t work. But now, he doesn’t need to wear a mask, and can even play in the dirt (story here).

Additionally, gene editing was used by Lawrence, PhD, and her team to insert Xist into an extra chromosome 21 in Down syndrome stem cells, effectively silencing the whole chromosome and reversing the effects of trisomy 21 (see my blog post on this topic).

Very recently, it has been successfully used to treat HIV!

Only a month ago, the New England Journal of Medicine published a University of Pennsylvania study reporting successful genetic engineering of human T cells to resist HIV infection. In it, the authors describe how they engineered human T cells (one of the immune system cells targeted by the human immunodeficiency virus, or HIV) with the CCR5-delta-32 mutation. This mutation actually exists naturally in some people, giving them built-in resistance to HIV infection. See, this CCR5 gene encodes a T cell surface protein that the virus uses to gain entrance into the cell, so without it, the T cells are much safer. Unfortunately, some strains of HIV also use a different surface protein (CXCR4) to gain access, so this method alone is not a perfect cure for HIV (Coakley et al., 2005), but it definitely helped the 12 HIV positive patients in this study that were infused with these modified cells. In fact, one patient’s viral load dropped below the detectable level! You can read more about this study here.

Upcoming Developments:

A research group at the Parkinson’s Institute is currently making progress toward a cure for Parkinson’s disease. Sangamo Biosciences is working with CHDI Foundation, Inc. on a cure for Huntington’s disease. Investigators at Howard Hughes Medical Institute have already cured hemophilia in mice, which is very promising for humans with this disease. Cystic fibrosis, Sickle cell anemia, pretty much any genetic disorder you can think of, people have already cured in human stem cells and even animals.

Once these cures become available, the biggest area of biomedical research will be to identify the genetic basis for diseases that are less well understood. For example, researchers at Trinity College claim to have identified a genetic mutation associated with bipolar disorder and schizophrenia (read here). Once these problem genes are targeted, gene editing will take care of the rest. A tidal wave of human cures is on its way.

This is a huge deal.

Being able to edit our genes is something researchers have been working towards ever since they figured out what genes were. You might say, Well, genetic engineering has been around for quite some time. And it has. I mean, it was way back in 1973 that Herbert Boyer and Stanley Cohen created the very first genetically modified organism (GMO): an antibiotic resistant E. coli bacterium (yikes, by the way). But now we’re capable of doing it safely in humans. We have the power to genetically modify ourselves. I think that I also speak for Bill Nye when I say: “That’s WILD!”

…It’s also scary.

I don’t think I need to spell out the ethical implications. I mean, yes please let’s cure all the things! But along with that will come the power to change eye color, skin color, muscle development, and—God forbid—engineer new diseases.

It’s getting real. 

This Daily Mail article describes how the UK parliament will vote sometime before July on whether to approve a new IVF treatment involving the replacement of mutation-carrying mitochondrial DNA with a healthy donor’s mtDNA. If passed, this law would be the first to allow the creation of genetically modified human babies.


If any science fiction writers out there are currently struggling with writer’s block, try this one on for size: perhaps one day we’ll help evolution along by engineering new genes. For instance, a gene network might be added during fetal development that allows the human to breathe both on land and underwater. Who knows?

But really, guys, we’re entering a new era of human history. Get excited.


Discussion Topic: Opinions, please. I know you have them. Alternatively, write about new features you would like the human species to incorporate into its genome in the future.



One thought on “Gene Editing, Part II: It’s Freaking Insane

  1. Pingback: Real Life Love Potion Coming Soon | SciCrazy

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