A company called Genomic Prediction has confirmed that at least one woman is pregnant with embryos selected after analysing hundreds of thousands of DNA variants to assess the risk of disease. It is the first time this approach has been used for screening IVF embryos, but some don’t think this use of the technology is justified.
“Embryos have been chosen to reduce disease risk using pre-implantation genetic testing for polygenic traits, and this has resulted in pregnancy,” Laurent Tellier, CEO of Genomic Prediction, told New Scientist. He didn’t say how many pregnancies there were, or what traits or conditions were screened for.
While a few genetic mutations lead to serious disorders, the effect of most DNA changes is much less clear-cut. A particular mutation may only very slightly raise the risk of heart disease or cancer, for instance. Geneticists attempt to work out the overall effect of thousands of mutations by sequencing people’s DNA and calculating a so-called polygenic risk score, but there are big questions about how accurate or useful these are.
Genomic Prediction, which is based in New Jersey, is the first company to offer polygenic risk scores for embryos rather than adults, including an option to screen out embryos deemed likely to have very low IQ.
Using polygenic risk scores to screen embryos is controversial. “It is inappropriate to use pre-implantation genetic diagnosis to screen out polygenic risk factors for things like cardiovascular disease,” says Frances Flinter at Guy’s and St Thomas’ NHS Foundation Trust in the UK. “I think it’s a misuse of the technology.”
Such screening places undue emphasis on genetics when it isn’t the biggest factor, she says. For most of us, our risk of heart disease is determined by our diet, whether we smoke, how much exercise we take and so on.
“It’s completely different from using pre-implantation genetic diagnosis to select out embryos at high risk of a very serious disorder, when we can predict with complete accuracy whether or not those embryos will be affected,” says Flinter.
But Steven Hsu, one of the founders of Genomic Prediction, says polygenic scores reveal that a few people – those with the top 3 per cent of scores – have a dramatically higher risk of, say, breast cancer or heart disease. The company’s tests aim to identify these outliers.
“These results are very new,” says Hsu. “A typical pre-implantation genetic diagnosis expert who focuses on single gene conditions might not be aware of how strong the polygenic predictions can be.”
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