The scientists, at the Francis Crick Institute in London, hope this approach will shed light on early stages of life, reduce miscarriages and potentially improve fertility treatments.
'We would really like to understand the genes needed for a human embryo to develop successfully into a healthy baby,' lead scientist Dr Kathy Niakan told The Telegraph. 'The reason why it is so important is because miscarriages and infertility are extremely common, but they're not very well understood. You never can predict where the research will lead, but we hope it would be a great benefit for fertility treatments in the long term.'
The team applied for a licence to use the CRISPR/Cas9 genome-editing technology in September 2015 (see BioNews 820), and the HFEA met to consider their application on 14 January 2016. They are expected to report their decision shortly.
By using this tool, the researchers plan to 'turn off' up to four genes in a human embryo while it is still at the single-cell stage to find out whether they are crucial for early human development. They will then monitor how the embryos grow until they are one week old, when they will be destroyed.
All of the embryos used for the study are spare frozen IVF embryos, donated by couples undergoing treatment. It is estimated that around 20 to 30 embryos will be required per gene, so in total about 120 embryos may be needed.
If the HFEA approves, Dr Niakan and her team could be the first researchers outside of China to edit human embryos (see BioNews 799). However, authorisation from a separate ethics committee would also be needed until the team could start the work.
Out of 100 eggs fertilised during IVF, fewer than 50 reach the blastocyst stage, 25 implant into the womb and only 13 develop beyond three months. Why these rates are so low is something that the proposed research aims to explain. This could help doctors to recognise which embryos have the best chance of resulting in a successful pregnancy.
Although animal studies have helped scientists understand how some embryos develop, there are significant differences between mice and people – some genes are not expressed the same way or some are not expressed at all. Therefore, the UK team argue that they need to study human embryos directly.
However, some people oppose the use of gene editing in human embryos for safety and ethical reasons, and say that altering the DNA of an embryo is a step too far.
Dr Calum MacKellar, Director of Research of the Scottish Council on Human Bioethics told The Telegraph: 'Allowing the gene editing of embryos opens the road to genetically modifying all the descendants of a person as well as full blown eugenics, which was condemned by all civilised societies after the Second World War.
'It is the very future of the way in which societies accept persons with disabilities that is at play since such gene-editing procedures infer that they should not have been brought into existence.'
The research has also received support from others. Sarah Norcross, Director of the Progress Educational Trust, which publishes BioNews, said: 'This is an important piece of basic scientific research. Recurrent miscarriage affects a huge number of people and it isn't greatly understood. People are just told to go away and try again. To improve our understanding of something like that, which has a huge impact on people, is really valuable.'