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Study Finds Rare Resistance to Serious Genetic Diseases

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Scientists have found a rare genetic resilience that allows people to carry serious disease-causing genes without becoming affected. The results are reported online in the journal Nature Biotechnology. 

There are many, many kinds of genetic conditions. For this study, the scientists focused on a class known as Mendelian disorders (after famed botanist and geneticist Gregor Mendel), which are generally caused by mutations in a single gene. These mutations are considered penetrant: that is, if someone has one of these mutations, they will inevitably develop the associated disease. The researchers looked at eight severe conditions that exclusively affect children: cystic fibrosis, Smith-Lemli-Opitz syndrome, familial dysautonomia, epidermolysis bullosa simplex, Pfeiffer syndrome, autoimmune polyendocrinopathy syndrome, acampomelic campomelic dysplasia, and atelosteogenesis. By focusing on childhood-onset illnesses, the researchers could be sure that their adult study subjects were past the point of developing—or not developing—symptoms.

The study is part of the Resilience Project, which investigates what makes people healthy (as opposed to most medical research, which looks at how and why people get sick). Researchers reviewed the genomic data of 589,306 healthy volunteers from 12 different studies and organizations, including the DNA-testing company 23andMe. Within each genome, the scientists screened 874 genes, looking for mutations associated with disease.

Out of nearly 600,000 healthy participants, just 13 people carried the mutations—but none of them were, or ever had been, sick with any Mendelian condition. Something in their genes had intervened, although we don’t know exactly what that something is yet. The researchers say the findings indicate that perhaps these mutations aren't as penetrant as we thought.

"The identification of resilient individuals may provide a first step toward uncovering protective genetic variants that could help elucidate the mechanisms of Mendelian diseases and new therapeutic strategies," they write.

Unfortunately, those outcomes aren't going to directly result from this study for a very specific reason: the researchers don't know who these 13 resilient individuals are. Attempts to contact them were unsuccessful, in part because the consent forms they signed did not include permission to follow up. The researchers were therefore unable to get more information from these people, or to tell them about their resilience and the mutations they carried. 

“There’s an important lesson here for genome scientists around the world: the value of any project becomes exponentially greater when informed consent policies allow other scientists to reach out to the original study participants,” study co-author Stephen Friend said in a press statement. “If we could contact these 13 people, we might be even closer to finding natural protections against disease. We anticipate launching a prospective study in the future that will include a more broadly useful consent policy.”

Still, the study's preliminary results suggest that there are two ways to study a mutation-related condition: through people who have symptoms, and through those who seem healthy.

“Most genomic studies focus on finding the cause of a disease, but we see tremendous opportunity in figuring out what keeps people healthy,” co-author Eric Schadt said. “Millions of years of evolution have produced far more protective mechanisms than we currently understand. Characterizing the intricacies of our genomes will ultimately reveal elements that could promote health in ways we haven’t even imagined.”

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Food
Researchers Pinpoint the Genes Behind the Durian's Foul Stench
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Durian is a popular fruit in parts of southeast Asia. It's also known for having the most putrid, off-putting odor of any item sold in the produce section. Even fans of durian know why the fruit gets a bad rap, but what exactly causes its divisive scent is less obvious. Determined to find the answer, a team of researchers funded by "a group of anonymous durian lovers" mapped the fruit's genome, as reported by the BBC.

The study, published in the journal Nature Genetics [PDF], contains data from the first-ever complete genetic mapping of a durian fruit. It confirms that durian's excess stinkiness comes from sulfur, a chemical element whose scent is often compared to that of rotten eggs.

Analysis of the fruit's chemical makeup has been done in the past, so the idea that sulfur is a major contributor to its signature smell is nothing new. What is new is the identification of the specific class of sulfur-producing genes. These genes pump out sulfur at a "turbocharged" rate, which explains why the stench is powerful enough to have durian banned in some public areas. It may seem like the smell is a defense mechanism to ward off predators, but the study authors write that it's meant to have the opposite effect. According to the paper, "it is possible that linking odor and ripening may provide an evolutionary advantage for durian in facilitating fruit dispersal." In other words, the scent attracts hungry primates that help spread the seeds of ripe durian fruits by consuming them.

The revelation opens the door to genetically modified durian that are tweaked to produce less sulfur and therefore have a milder taste and smell. But such a product would likely inspire outrage from the food's passionate fans. While the flavor profile has been compared to rotten garbage and dead animal meat, it's also been praised for its "overtones of hazelnut, apricot, caramelized banana, and egg custard" by those who appreciate its unique character.

[h/t BBC]

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Why DNA Is So Hard to Visualize
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Picture a strand of DNA and the image you see will likely be similar to the artist’s rendering above. The iconic twisted ladder, or double-helix structure, was first revealed in a photo captured by Rosalind Franklin in the 1950s, but this popular visualization only tells part of the story of DNA. In the video below, It’s Okay to Be Smart explains a more accurate way to imagine the blueprints of life.

Even with sophisticated lab equipment, DNA isn’t easy to study. That’s because a strand of the stuff is just 2 nanometers wide, which is smaller than a wavelength of light. Researchers can use electron microscopes to observe the genetic material or x-rays like Rosalind Franklin did, but even these tools paint a flawed picture. The best method scientists have come up with to visualize DNA as it exists inside our cells is computer modeling.

By rendering a 3D image of a genome on a computer, we can see that DNA isn’t just a bunch of free-floating squiggles. Most of the time the strands sit tightly wound in a well-organized web inside the nucleus. These balls of genes are efficient, packing 2 meters of DNA into a space just 10 millionths of a meter across. So if you ever see a giant sculpture inspired by an elegant double-helix structure, imagine it folded into a space smaller than a shoe box to get closer to the truth.

[h/t It’s Okay to Be Smart]

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