“Custom Baby” Bigger and Smarter? Scientists give technical answers

The controversial topic of “custom babies” has always made waves as the human son’s own “codebook” begins to be decoded. In 2017, Delaware-based start-up Genomic Prediction plans to offer an in vitro fertilization (IVF) embryo test that sifts throughout the genome for cognitive-related DNA mutations to help couples avoid having children with intellectual disabilities.

(Original title: “Custom baby” taller and smarter? Ethics aside, scientists give technical answers)

这些基因检测公司宣称理论上可行的消息让许多伦理学家担心,多基因分析有朝一日可能也会被用于筛选胚胎,最终“定制”身材高大或智商高的婴儿。

A paper published in Cell, the world’s top academic journal, may allay fears. Shai Carmi, a statistical geneticist at the Hebrew University of Jerusalem, and colleagues simulated the feasibility of screening embryos based on traits caused by multiple genes, such as IQ and height, and chose the highest-scoring embryos to accurately calculate the expected range of IQ or height increases.

The result: the gains are minimal, and the tallest or brightest offspring may even be abandoned. This means that current technology does not provide perfect support for “custom babies”.

Such tests are based on a polygene risk score, a tool used to assess an individual’s likelihood of developing a disease or having a certain characteristic. Some direct-to-consumer gene testing companies have begun to provide customers with multi-gene risk scores for diseases such as heart disease, breast cancer and diabetes.

However, testing embryos is controversial. On the one hand, the test sits still scientifically limited, and on the other hand, the future of “custom babies” is uncertain. Genomic Prediction is trying to get millions of DNA markers from cell testing extracted from IVF embryos in 2018 to arrive at a risk score for common diseases and “intellectual disabilities” or low IQs.

Stephen Hsu, co-founder of Genomic Prediction and a physicist at Michigan State University, has previously said the company’s technology has been used to screen out high-IQ babies. However, the company is not officially on the market to offer such services, because “society is not ready.”

Still, some scientists believe the “custom baby” era may soon be upon us. Carmi, who presented his research at the annual meeting of the American Society for Human Genetics (ASHG) before his official paper, said at the meeting that most people thought it was not a good idea, but there was no data to prove it.

To find out if a “custom baby” was feasible, the Carmi team created a simulated genome for potential embryos by combining the DNA profiles of “parents.” These “parents” included 102 pairs of actually or randomly paired German Men and Women with height records, and another 919 pairs of Randomly Matched Greeks with cognitive test scores.

The team made a simulation on a computer that assumed that each couple would have 10 embryos to choose from, and then predicted the IQ or adult height of each offspring based on genetic variation in the simulated embryo genome.

It turns out that the expected advantage of these theoretical descendants is relatively small. In terms of IQ, it increased to a high of 2.5 points above the average for embryos. For height, it increases to a maximum height of 2.5 cm above the average height.

The above theoretical values may not be realized. Carmi’s team also studied the genomes of the adult children of the 28 large families (an average of 10 children) who actually existed. They found that unknown environmental impacts (which may include factors such as diet) and genes not reflected in multigene scores, in terms of height, clearly overwhelmed the genetic markers included in the assessment. In one family, the highest-scoring child may be shorter than the average height of all other siblings.

Although Carmi’s team does not have such real-life IQ data, Peter Joshi, a demogeneticist at the University of Edinburgh, predicts that any intellectual multi-gene fraction is less reliable. “You’re probably wrong as many times as you did,” Joshi said. “

Melinda Mills, a sociologist and demographer at the University of Oxford in the UK, said the work was “the first empirical test of the feasibility of screening embryos” to identify ideal characteristics affected by many genes, such as height and high IQ. She concluded that the embryo screening was beyond the current tests for single-gene disease and was “unlikely” at the moment.

In addition, Joshi believes such tests are unethical. But Hsu stresses that genomic prediction is to avoid embryos with rare “abnormal” DNA traits that indicate a high risk of having an IQ below 75, or intellectual disability.

It’s worth noting that this multi-gene risk score for IQ and disease may improve as researchers look for genetic markers in larger, more diverse populations. “What happens when they are really predictable?” In response to this problem, Alexander Young, a statistical geneticist at the University of Oxford, argues that “this equation can change”.

The ethical debate over this bold embryo screening is only just beginning, the researchers believe.

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