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Scientists Remove Disease-Causing Mutations from Human Embryos

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Researchers have successfully edited the genes of viable human embryos to repair mutations that cause a dangerous heart condition. The team published their controversial research in the journal Nature.

The versatile gene-editing technique known as CRISPR-Cas9 is no stranger to headlines. Scientists have already used it to breed tiny pigs, detect disease, and even embed GIFs in bacteria. As our understanding of the process grows more advanced and sophisticated, many researchers have wondered how it could be applied to human beings.

For the new study, an international team of researchers fertilized healthy human eggs with sperm from men with a disease called hypertrophic cardiomyopathy, a condition that can lead to sudden death in young people. The mutation responsible for the disease affects a gene called MYBPC3. It’s a dominant mutation, which means that an embryo only needs one bad copy of the gene to develop the disease.

Or, considered another way, this means that scientists could theoretically remove the disease by fixing that one bad copy.

Eighteen hours after fertilizing the eggs, the researchers went back in and used CRISPR-Cas9 to snip out mutated MYBPC3 genes in some of the embryos and replace them with healthy copies. Three days later, they checked back in to see how their subjects—which were, at this point, still microscopic balls of cells—had fared.

The treatment seemed successful. Compared to subjects in the control group, a significant number of edited embryos appeared mutation- and disease-free. The researchers also found no evidence that their intervention had led to any unwanted new mutations, although it is possible that the mutations were there and overlooked.

Our ability to edit human genes is improving by the day. But, many ethicists argue, just because we can do it doesn’t mean that we should. The United States currently prohibits germline editing of human embryos by government-funded researchers. But there’s no law against such experimentation in privately funded projects like this one.

The same day the new study was published, an international committee of genetics experts issued a consensus statement advising against editing any embryo intended for implantation (pregnancy and birth).

"While germline genome editing could theoretically be used to prevent a child being born with a genetic disease, its potential use also raises a multitude of scientific, ethical, and policy questions,” Derek T. Scholes of the American Society of Human Genetics said in a statement. “These questions cannot all be answered by scientists alone, but also need to be debated by society."

Ethicists and sociologists are concerned by the slippery slope of trying to build a better human. Many people with chronic illness and disability live happy, complete lives and report that they’re limited more by discrimination than by any medical issues.

Disability studies expert Lennard Davis of the University of Illinois says we can’t separate scientific decisions from our society’s history of violence against, and oppression of, disabled and sick people.

“A lot of this terrific science and technology has to take into account that the assumption of what life is like for people who are different is based on prejudice against disability,” he told Nature in 2016.

Rosemary Garland-Thomson is co-director of the Disability Studies Initiative at Emory University. Speaking to Nature, she said we are at a cultural and ethical precipice: “At our peril, we are right now trying to decide what ways of being in the world ought to be eliminated.”

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Animals
How a Pregnant Rhino Named Victoria Could Save an Entire Subspecies
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Sudan, the last male member of the northern white rhino subspecies, while being shipped to Kenya in 2009
Tony Karumba, AFP/Getty Images

The last male northern white rhino died at a conservancy in Kenya earlier this year, prompting fears that the subspecies was finally done for after decades of heavy poaching. Scientists say there's still hope, though, and they're banking on a pregnant rhino named Victoria at the San Diego Zoo, according to the Associated Press.

Victoria is actually a southern white rhino, but the two subspecies are related. Only two northern white rhinos survive, but neither of the females in Kenya are able to reproduce. Victoria was successfully impregnated through artificial insemination, and if she successfully carries her calf to term in 16 to 18 months, scientists say she might be able to serve as a surrogate mother and propagate the northern white rhino species.

But how would that work if no male northern rhinos survive? As the AP explains, scientists are working to recreate northern white rhino embryos using genetic technology. The San Diego Zoo Institute for Conservation Research has the frozen cell lines of 12 different northern white rhinos, which can be transformed into stem cells—and ultimately, sperm and eggs. The sperm of the last northern white male rhino, Sudan, was also saved before he died.

Scientists have been monitoring six female southern white rhinos at the San Diego Zoo to see if any emerge as likely candidates for surrogacy. However, it's not easy to artificially inseminate a rhino, and there have been few successful births in the past. There's still a fighting chance, though, and scientists ultimately hope they'll be able to build up a herd of five to 15 northern white rhinos over the next few decades.

[h/t Time Magazine]

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entertainment
Why Our Brains Love Plot Twists
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From the father-son reveal in The Empire Strikes Back to the shocking realization at the end of The Sixth Sense, everyone loves a good plot twist. It's not the element of surprise that makes them so enjoyable, though. It's largely the set-up, according to cognitive scientist Vera Tobin.

Tobin, a researcher at Case Western Reserve University, writes for The Conversationthat one of the most enjoyable moments of a film or novel comes after the big reveal, when we get to go back and look at the clues we may have missed. "The most satisfying surprises get their power from giving us a fresh, better way of making sense of the material that came before," Tobin writes. "This is another opportunity for stories to turn the curse of knowledge to their advantage."

The curse of knowledge, Tobin explains, refers to a psychological effect in which knowledge affects our perception and "trips us up in a lot of ways." For instance, a puzzle always seems easier than it really is after we've learned how to solve it, and once we know which team won a baseball game, we tend to overestimate how likely that particular outcome was.

Good writers know this intuitively and use it to their advantage to craft narratives that will make audiences want to review key points of the story. The end of The Sixth Sense, for example, replays earlier scenes of the movie to clue viewers in to the fact that Bruce Willis's character has been dead the whole time—a fact which seems all too obvious in hindsight, thanks to the curse of knowledge.

This is also why writers often incorporate red herrings—or false clues—into their works. In light of this evidence, movie spoilers don't seem so terrible after all. According to one study, even when the plot twist is known in advance, viewers still experience suspense. Indeed, several studies have shown that spoilers can even enhance enjoyment because they improve "fluency," or a viewer's ability to process and understand the story.

Still, spoilers are pretty universally hated—the Russo brothers even distributed fake drafts of Avengers: Infinity War to prevent key plot points from being leaked—so it's probably best not to go shouting the end of this summer's big blockbuster before your friends have seen it.

[h/t The Conversation]

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