Photo: Jaillon et al., 2004 / UVM Genetics & Genomics Wiki

Is human embryo genome editing the future of medicine?

Scientists in China are pushing at the frontiers of genetics – they have carried out the first set of experiments on genome-editing in human embryos, However, this research raises important ethical dilemmas for the scientific community.

In April this year, researchers at Sun Yat-sen University in Guangzhou published a landmark paper on genome-editing in human embryos, but the significance of the research lies not in the results, but in the fact that it is the first to openly conduct research in this uncertain ethical territory.

After the paper’s publication, the influential journal Nature published an article from leading scientists calling for a worldwide ban on genome-editing research in human embryos.

However, now it seems the tide may slowly be shifting in its favour: a group of scientists have come out in support of the research and the first UK application for a research licence to conduct genome editing in human embryos has been submitted. A decision is still pending.

The idea of treating inherited disorders directly at their source is appealing, however there are also ethical and practical issues to consider

So what is human embryo genome-editing and why is it controversial?

Genome-editing uses a system derived from bacteria called CRISPR/Cas9, which, when introduced into a cell, uses a ‘find and replace’ mechanism to replace unwanted segments of DNA with new ones designed by the researcher.

Because the system is highly versatile, it can be targeted to almost any gene within a cell, and relatively easy to use, if applied in human embryos it could be a powerful weapon in the fight against inherited disease.

A baby in the womb Photo: Dr. Wolfgang Moroder / Wikimedia Commons

A baby in the womb Photo: Dr. Wolfgang Moroder / Wikimedia Commons

Repairing a faulty gene in a single embryo would eradicate the disease from its future germline, ensuring not only that the treated embryo is disease-free, but that its future offspring are too.

The idea of treating inherited disorders directly at their source is appealing, however there are also ethical and practical issues to consider. One of the caveats of CRISPR/Cas9 is the unpredictability with which it introduces changes to DNA.

Although attached ‘guide’ sequences target CRISPR/Cas9 to specific sequences in the genome, there is still the risk that the system will introduce additional off-target edits in random regions of the genome. This could lead to unpredictable effects that may not manifest until later in life, or possibly even a few generations down the line. It is likely that future research into genome-editing in human embryos, if given the go-ahead, will focus on ways to minimise these spurious changes.

Of course, no treatment – from a simple blood test to open-heart surgery – is completely risk-free, but what makes genome-editing different from other forms of medical treatment is its inheritability. It places caregivers in the unique situation of treating an individual and that individual’s future offspring.

This raises questions about informed consent: in the case of changes to the germline, how does a person who doesn’t yet exist consent to treatment?

It is hard to imagine anyone raising concerns about having a life-altering disease edited out of their genome, especially if that treatment is the reason for their very existence. But the versatility of CRISPR/Cas9 system means that genes that are not associated with disease could be altered, opening up the potential for exploitation. Why stop at alterations to genes that cause disease? Why not make our children smarter, taller, stronger, and so on?

Although a decision on the application for human embryo research is still pending, one thing is clear –genome-editing is here and it is here to stay.

Many of the concerns raised about the technique refer to its potential clinical application, but for a method still in its infancy, that day is still far off. In a controlled research environment, under close regulation, the pursuit of knowledge and expertise in this area will be valuable.

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