Editing human embryos is genetics' new battleground
Date: 16.3.2015
Replacing faulty genes in early human embryos and germ cells is within our grasp. Such changes affect DNA in the nucleus and so would be heritable; ultimately, they could be used to make a genetically modified baby.
There are already reports that groups in China, the US and the biotech industry have done this kind of genetic engineering in the lab, prompting some scientists to call for a moratorium on this work. But the underlying technology is potentially hugely disruptive, offering easier and more precise ways to manipulate genes. Here's what you need to know about this new frontier in genetics.
What's behind the current controversy over human genetic engineering?
Several teams have tried modifying the genome of a human embryo and submitted their results for publication, according to an article published in Technology Review on 5 March. This kind of research is already illegal in some countries.
What exactly has been done?
We don't know the details yet. But based on what's been done in monkeys, the work probably involved fertilising donated human eggs by injecting a sperm and then, while the fertilised eggs were still at the one-cell stage, injecting various RNAs. These RNAs cut DNA at specific sites, tricking our natural DNA repair system into destroying or replacing one or more genes – a technique known as gene editing. The embryos would then have been allowed to develop for a few days until they reached the blastocyst stage – containing a few hundred cells – before being destroyed. The embryos' DNA would have been sequenced to see whether the gene editing had been successful.
So it's now possible to genetically engineer humans?
It was already possible. The hard part is doing it safely and efficiently. Gene editing was first developed decades ago, but it was very difficult and expensive, and often didn't work very well. To create just one genetically modified animal this way typically required hundreds of attempts. But editing genes has become a lot easier, cheaper and more efficient thanks to the CRISPR system, developed just a couple of years ago. This was the method used to modify the human embryos.
