Genetically modified human embryos

By Peter Dearden 07/05/2015

Peter K. Dearden

You may have missed it but last month the world of human genetics changed. A group of Chinese scientists published a paper describing the first genetically modified human embryos, opening a route to germ-line modification of our own species. This is an ethically troubling, but perhaps inevitable, technological break-through. We are now all challenged with a question that we really should have thought more carefully about before this happened.

Firstly it is important to discuss what they did. Using a technique called genome editing, the researchers tried to manipulate a gene in the human genome that, when mutant, is associated with a human disease beta-thalassemia. Genome editing uses a complex method, based on a bacterial defence system, to target specific sequences in a genome and change them. This technology has been used in many animals, but not yet in humans, and is ideal for repairing mutations in genes that would otherwise lead to disease.

The scientists used human embryos from IVF, but selected those that had three nuclei, meaning they had been fertilised by two sperm. This means that the embryos they used are non-viable; this was a test of the technology, and not an attempt to make GM children.

The scientists found that the technology was not entirely effective in humans, causing changes in the genome away from the site they were targeting, and affecting a second gene related to the one they were aiming for. They conclude that more research and optimisation of the technique is required to make it work effectively.  The key point is, however, that while it is wasteful and inefficient, it works. You can, and they have, made genetically modified human embryos.

This work clearly aims to develop technologies that will allow the repair of genetic defects in early human embryos. By identifying disease-causing mutations, by commonly used genetic techniques, and then repairing them with genome editing, it may be possible to relieve the burden of some inherited human genetic disorders. The real problem is, however, that what you are editing is the human germline.

Previous attempts to modify the human genome to treat disease used viral vectors to add back missing or damaged genes. This process was applied to children or adults, and usually didn’t affect the germ-line; the cells that make the next generation.

In this case, genome editing was applied at such an early stage that all cells of the embryo, including the germline, were changed. This form of genetic modification would thus not just affect the embryo being manipulated, but all its subsequent offspring. This is a permanent change to the DNA in a whole lineage of people.

So the question is, do we want to do this? This could be a solution to some human genetic diseases, but the technology could be used for non-disease related uses. The changes made are permanent, and traits produced would be passed on from generation to generation. We desperately need to understand what people think of this technology, if there is a way to draw a line on its use, and if there are reasons to use it at all. Personally I think we need to stop, think and consult about what is happening, and clearly define why this technology might need to be used. This is a frightening and potentially dangerous technology. Let’s think carefully before we use it.

More problematically, and something I would be delighted to have input on, is how do we have such discussions? How do we get a nation, or humankind, to think about the impact of such technologies and make informed decisions?

This is an important technology. How we use it (or don’t) will have impacts for generations to come.