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Researchers Find Genetic Regions Associated with Depression

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Depression is one of the most common mental health conditions in the world. In 2014 alone, an estimated 15.7 million American adults reported having at least one depressive episode. Scientists have been saying for decades that depression is a real illness with multiple physiological causes, yet we tend to treat it like it’s a shameful character flaw or a choice. A new study puts another nail in the coffin of that harmful fallacy: Researchers have identified 15 areas of the genome that are significantly more common in people with major depressive disorder (MDD). They published their findings today in the journal Nature Genetics.

MDD, also known as clinical depression, can turn lives upside down. People with depression are not "just sad"; they’re facing down symptoms like fatigue, loss of appetite, physical pain, feelings of hopelessness, and trouble concentrating. Depression can make it very hard to work or engage with loved ones.

The good news is that treatments are available. The bad news is that everyone’s depression is different, and finding the right treatment can take time. Researchers are hard at work learning everything they can about the causes and physiology of depression, because the more we know, the more effective our treatments can become.

We’ve known for a while that depression tends to run in families, but the details of that genetic component have largely remained elusive. One previous study of more than 10,000 Chinese women had already looked into, and found, genetic regions associated with depression, and researchers wanted to know if they might be able to find similar traces in other people.

Fortunately, we’re living in an age of crowd sourcing and quantified everything, when getting your DNA tested is as simple as mailing off a swab covered with your saliva. Millions of people are submitting their samples to testing companies like 23andMe, and many of them have agreed to make their results available to researchers. So the team pulled genetic data on more than 300,000 23andMe users of European descent. Of those volunteers, 75,607 said they’d been diagnosed with or treated for clinical depression.

The researchers then scanned all the participants’ genomes, looking for potential areas of overlap. They found them: 17 genetic variations—specifically, single nucleotide polymorphisms, or SNPs—spread through 15 regions of the DNA of people with depression. Further analysis showed that those 15 regions are hotspots for genes expressed in the nervous system and those associated with brain development. And previous studies have already linked those regions to other mental health issues.

Like its predecessor, this study looked at one specific group of people of similar descent, most of whom were women (62 percent). So while the results are not universal, they nevertheless underscore the crucial role of genetics in mental health.

Roy Perlis is a medical director at the Department of Psychiatry and the Center for Human Genetic Research at Massachusetts General Hospital, as well as co-corresponding author on the paper.

"Identifying genes that affect risk for a disease is a first step toward understanding the disease biology itself, which gives us targets to aim for in developing new treatments," Perlis said in a press statement. "More generally, finding genes associated with depression should help make clear that this is a brain disease, which we hope will decrease the stigma still associated with these kinds of illnesses."

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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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