赤ちゃんの遺伝子を選ぶ？ 倫理的な議論沸騰

Get the latest on the science of healthy living in the NPR Health newsletter, sent weekly.Justin Schleede reaches onto a black lab bench to pick up a tray of small plastic tubes.

Related Story: NPR"These are saliva samples as well as blood," says Schleede, a geneticist who runs Herasight Inc.'s lab in Morrisville, N.C. "We also get cells from the embryos."Herasight, which is named after Hera, the Greek goddess associated with fertility, is one of a handful of new companies that analyze samples like these for a controversial new type of genetic testing: polygenic embryo screening.Like high-tech fortune-telling, the screening estimates the chances that embryos will produce children at risk for thousands of illnesses, from rare inherited disorders such as Tay-Sachs and cystic fibrosis to common diseases with genetic factors such as cancer, heart disease, diabetes and Alzheimer's."For people that are risk averse and don't want to simply roll the dice, they come to us to try to get as much genomic information to pick embryos for the purpose of having happy, healthy, disease-free children," says Schleede.Some companies, like Orchid Health, based in Palo Alto, Calif., only calculate health risks. Herasight goes further by also predicting height, BMI, longevity and even IQ. Nucleus Genomics in New York lets prospective parents try to select even more traits, including eye color, hair color, propensity for baldness and acne, and whether a child will be left-handed."We call it genetic optimization," says Kian Sadeghi, founder and CEO of Nucleus Genomics. "We help people have their best babies. "The companies compile polygenic risk scores, a numerical estimate, based on genetic variants, of the chances for developing certain diseases and traits. Clients use the scores to pick which embryos to use to try to have children.But the American College of Medical Genetics and Genomics and the American Association of Reproductive Medicine say the science of polygenic risk scores hasn't progressed enough to produce reliable estimates. Beyond genes, the environment and lifestyle are important factors for many diseases. Some also argue the screening raises troubling moral, ethical and societal concernsScience fiction inches toward realityPolygenic risk screening for embryos is part of what some futurists have dubbed the "Gattaca Stack." Named after the 1997 movie that envisioned a dystopian society of genetic selection, the Gattaca Stack would combine technologies like polygenic embryo screening with embryo editing, artificial wombs and lab-grown eggs and sperm to create genetically enhanced humans."I'm very worried about the kind of dystopian world that this way of using technologies could lead to," says Katie Hasson, the executive director of the Center for Genetics and Society. "At its heart, it's a vision of … mass-produced, genetically enhanced people, right? It's an idea of doing genetic engineering at scale with some vision of producing a superior form of humanity, which I think is very troubling."But Schleede and his colleagues, as well as officials at other companies, defend their services. They say their estimates are very reliable and focused primarily on preventing disease — not creating some kind of master race."I understand. It does sound kind of scary. It sounds like, 'Oh my God. Is this like Gattaca?'" says Sadeghi of Nucleus Genomics."But people want their baby to be like themselves — like a better version of themselves. That's what parents really want," he says. "They don't want some kind of superbaby. And when I think when people understand then suddenly things become much less scary." Anxious parents look for reassurance Christian Ward, 32, a tax accountant who lives in Las Vegas with his wife, signed up for that company's services primarily to try to cut the chances of having a baby with Type 1 diabetes, which Ward has."It's really difficult to go from a healthy life to then being completely insulin dependent," says Ward. "It's just not something that I'd like to pass on to a child. I wouldn't want my child to be always thinking about their blood sugar and how to manage it."But he adds: "It's kind of trippy to think that you can kind of cycle through and see, 'Oh, this embryo could potentially have this hair color, this eye color,' all these other things.'"His wife, Julia, who's a nurse practitioner, wants a healthy baby."We're really excited. For us we're just mainly looking at the medical side of it," she says. "It kind of keeps you a little bit more calm. Having a new child is sometimes scary. It just gives us a sense of peace with everything."Max Reilly, who's 30 and lives in British Columbia, Canada, signed up for Herasight's services for similar reasons. He mainly wants to cut the risk of having a child at risk for Alzheimer's."I've been exposed to a few people with Alzheimer's in my life," he says. "It's just so tough on people and their loved ones. And to reduce the chances of someone having to go through that and their kids having to go through that is just awesome."But he and his wife are also interested in cutting the risk for other diseases, as well as having the smartest children possible."It's hard to imagine not wanting to be, you know, a little bit, a little bit smarter, a little bit sharper," Reilly says. "It is sort of out of science fiction. It's just science now. I think it's sort of incredible technological progress. I think it's very cool."How good are the predictions? But not everyone thinks this is such a great idea. First of all, it's expensive. As much as $50,000, plus thousands more for IVF, which is physically grueling and carries risks. Some people get their embryos screened if they're already going through IVF for infertility. Others do IVF specifically to produce embryos for screening."Polygenic risk scores for embryos [are] not yet ready for prime time," says Dr. Susan Klugman, a medical geneticist who served as the president of the American College of Medical Genetics and Genomics. "Polygenic risk scores for embryos are a new technology. And current evidence doesn't support their accuracy, their safety or their clinical value. So ethically we worry about misleading patients and overstating what the polygenic risk score can do."And that's especially true for complicated traits like IQ, she says.She's also worried that parents could inadvertently pick an embryo prone for some terrible disease missed by the testing."While you are selecting for blue eyes, let's say, we don't know if you are also selecting for a certain disease or disorder," Klugman says. "We just don't know."Some fear parents will be disappointed if the babies don't live up to their expectations."The thought would be: 'We paid for you to be smart. So why aren't you doing well in school? We paid for you to not have cancer. How can you have developed cancer?'" says James Tabery, a bioethicist at The University of Utah. "There's this illusion of control that doesn't actually exist. And if you are the product of that perceived control that doesn't exist, you can be targeted as the problem."But the companies dismiss the criticism. They say their estimates are state-of-the-art and have been carefully validated. Any new technology can be misused, and is often vilified initially, they say. Early genetic testing and IVF was initially condemned as dangerous by some, they note. Back in the labBack at Herasight, Schleede shows how polygenic risk scores are calculated.In one of the company's labs, scientists in blue gowns begin the process by removing DNA from the blood and saliva samples of couples and cells from their embryos."They move through this area, get processed — kind of cracking DNA out of cells – isolating the DNA and then prepping it to be used for analyses," Schleede explains.In the second lab, the DNA is frozen until scientists make millions of copies so genetic sequencers can spell out all three billion letters of the embryo's genetic sequence."Once we have the most accurate sequences then we can go and try to do all the downstream analyses," Schleede says.The computerized analysis produces polygenic risk scores using complex algorithms developed from years of genetic research on large databases."These are very predictive scores," says Schleede.Clients then use those polygenic risk scores to pick which embryos to use to try to have a baby."They're just trying to make happy, healthy kids that are just gonna to survive in the world as we see it today," Schleede says. So far these companies say they've scored thousands of embryos for hundreds of prospective parents – and have already helped create dozens, possibly hundreds, of genetically screened babies.

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