By CARL ZIMMER From biology class to “C.S.I.,” we are told again and again that our genome is at the heart of our identity. Read the sequences in the chromosomes of a single cell, and learn everything about a person’s genetic information — or, as 23andme, a prominent genetic testing company, says on its Web site, “The more you know about your DNA, the more you know about yourself.” But scientists are discovering that — to a surprising degree — we contain genetic multitudes. Not long ago, researchers had thought it was rare for the cells in a single healthy person to differ genetically in a significant way. But scientists are finding that it’s quite common for an individual to have multiple genomes. Some people, for example, have groups of cells with mutations that are not found in the rest of the body. Some have genomes that came from other people. “There have been whispers in the matrix about this for years, even decades, but only in a very hypothetical sense,” said Alexander Urban, a geneticist at Stanford University. Even three years ago, suggesting that there was widespread genetic variation in a single body would have been met with skepticism, he said. “You would have just run against the wall.” But a series of recent papers by Dr. Urban and others has demonstrated that those whispers were not just hypothetical. The variation in the genomes found in a single person is too large to be ignored. “We now know it’s there,” Dr. Urban said. “Now we’re mapping this new continent.” Dr. James R. Lupski, a leading expert on the human genome at Baylor College of Medicine, wrote in a recent review in the journal Science that the existence of multiple genomes in an individual could have a tremendous impact on the practice of medicine. “It’s changed the way I think,” he said in an interview. Scientists are finding links from multiple genomes to certain rare diseases, and now they’re beginning to investigate genetic variations to shed light on more common disorders. © 2013 The New York Times Company

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 18657 - Posted: 09.17.2013

By Shinnosuke Nakayama and The Conversation In our society, not many people are lucky enough to have an ideal boss who they would want to follow faithfully for the rest of their lives. Many might even find their boss selfish and arrogant or complain that they don’t listen to their opinions. We humans push the concept of leaders and followers to the extreme but they exist throughout the animal kingdom. These leaders and followers of the natural world could help us decide whether that unpopular boss can learn to be part of the team. Leaders and followers are found in many group-living animals, such as fish, birds and primates. Group living can offer many benefits to group members, such as increasing the chances of finding food or avoiding predators. Unlike some human workplaces, groups of animals know that they need to agree on where to go and when to go there in order to take full advantage of group living. Leaders share common characteristics, so are to some extent predictable. In humans, leaders generally show higher scores in certain personality traits, notably extraversion. Similarly, in animals, bolder and more active individuals tend to be found as leaders. Evolutionary theories suggest that boldness and leadership can coevolve through positive feedback. Individuals who force their preferences on others are more likely to be followed, which in turn encourages these individuals to initiate more often. This feedback results in distinct social roles for leaders and followers within a group, as shown by several experimental studies. It would therefore seem that leaders and followers are born through natural selection, and that you have no chance of becoming a leader if you are born a follower. But our work with stickleback fish suggests that while followers may not have what it takes to lead, leaders can learn to follow. © 2013 Scientific American

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 11: Emotions, Aggression, and Stress
Link ID: 18580 - Posted: 08.29.2013

By Tina Hesman Saey Genetic factors may exert a tiny influence on how much schooling a person ends up with, a new study suggests. But the main lesson of the research, experts say, should be that attributing cultural and socioeconomic traits to genes is a dicey enterprise. “If there is a policy implication, it’s that there’s even more reason to be skeptical of genetic determinism,” says sociologist Jeremy Freese of Northwestern University in Evanston, Ill. Published May 30 in Science by a group of more than 200 researchers, the study does mark the first time genetic factors have been reproducibly associated with a social trait, says Richard Ebstein, a behavioral geneticist at the National University of Singapore. “It announces to social scientists that some things they’ve been studying that make a difference to health and life success do have a base in genetics.” But even if it does survive further inspection — and many similar links between genes and social characteristics have not — the study accounts for no more than 2 percent of whatever it is that makes one person continue school while someone in similar circumstances chooses to move on to something else. Previous studies comparing twins and family members have suggested that not-yet-identified genetic factors can explain 40 percent of people’s educational attainment; factors such as social groups, economic status and access to education would explain the other 60 percent. That percentage attributed to genetics is similar to the heritability of physical and medical characteristics such as weight and risk of heart disease.That makes a hunt for the genetic factors underlying educational attainment an attractive prospect. © Society for Science & the Public 2000 - 2013

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 14: Attention and Higher Cognition
Link ID: 18211 - Posted: 06.01.2013

By Tina Hesman Saey COLD SPRING HARBOR, N.Y. – Taming foxes changes not only the animals’ behavior but also their brain chemistry, a new study shows. The finding could shed light on how the foxes’ genetic cousins, wolves, morphed into man’s best friend. Lenore Pipes of Cornell University presented the results May 10 at the Biology of Genomes conference. The foxes she worked with come from a long line started in 1959 when a Russian scientist named Dmitry Belyaev attempted to recreate dog domestication, but using foxes instead of wolves. He bred silver foxes (Vulpes vulpes), which are actually a type of red fox with white-tipped black fur. Belyaev and his colleagues selected the least aggressive animals they could find at local fox farms and bred them. Each generation, the scientists picked the tamest animals to mate, creating ever friendlier foxes. Now, more than 50 years later, the foxes act like dogs, wagging their tails, jumping with excitement and leaping into the arms of caregivers for caresses. At the same time, the scientists also bred the most aggressive foxes on the farms. The descendents of those foxes crouch, flatten their ears, growl, bare their teeth and lunge at people who approach their cages. The foxes’ tame and aggressive behaviors are rooted in genetics, but scientists have not found DNA changes that account for the differences. Rather than search for changes in genes themselves, Pipes and her colleagues took an indirect approach, looking for differences in the activity of genes in the foxes’ brains. © Society for Science & the Public 2000 - 2013

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 18164 - Posted: 05.16.2013

Ed Yong The US adolescents who signed up for the Study of Mathematically Precocious Youth (SMPY) in the 1970s were the smartest of the smart, with mathematical and verbal-reasoning skills within the top 1% of the population. Now, researchers at BGI (formerly the Beijing Genomics Institute) in Shenzhen, China, the largest gene-sequencing facility in the world, are searching for the quirks of DNA that may contribute to such gifts. Plunging into an area that is littered with failures and riven with controversy, the researchers are scouring the genomes of 1,600 of these high-fliers in an ambitious project to find the first common genetic variants associated with human intelligence. The project, which was launched in August 2012 and is slated to begin data analysis in the next few months, has spawned wild accusations of eugenics plots, as well as more measured objections by social scientists who view such research as a distraction from pressing societal issues. Some geneticists, however, take issue with the study for a different reason. They say that it is highly unlikely to find anything of interest — because the sample size is too small and intelligence is too complex. Earlier large studies with the same goal have failed. But scientists from BGI’s Cognitive Genomics group hope that their super-smart sample will give them an edge, because it should be enriched with bits of DNA that confer effects on intelligence. “An exceptional person gets you an order of magnitude more statistical power than if you took random people from the population — I’d say we have a fighting chance,” says Stephen Hsu, a theoretical physicist from Michigan State University in East Lansing, who acts as a scientific adviser to BGI and is one of the project’s leaders. © 2013 Nature Publishing Group,

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 1: Introduction: Scope and Outlook
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 20:
Link ID: 18159 - Posted: 05.15.2013

Stephen S. Hall Male sexual dysfunction is never pretty, even in nematodes. In normal roundworm courtship, a slender male will sidle up to a plump hermaphrodite, make contact, and then initiate a set of steps leading up to insemination: a sinuous backwards motion as he searches for the sexual cleft, a pause to probe, and finally the transfer of sperm. The whole business is usually over in a couple of minutes. “It's very slithery, and affectionate,” says Cornelia Bargmann, who has been observing the behaviour of this particular worm, Caenorhabditis elegans, for 25 years. Last October, scientists in Bargmann's laboratory at the Rockefeller University, New York, reported the discovery of a gene that seems to be crucial to successful mating. Disrupting the action of this gene causes male sexual confusion of almost epic pathos: nematodes with certain mutations poke tentatively at an inert hermaphrodite, making confused, fruitless curlicues around the potential mate. Occasionally the mutant male succeeds, but often he literally falls off the job and begins the search anew for a mate. Jennifer Garrison, a postdoc of Bargmann's who tracked the behaviour of these males, just shakes her head as she replays the scene on her computer screen. “Really sad,” she says. There are two punchlines to this story of thwarted invertebrate mating. One is the charming squeamishness with which Bargmann describes it, hesitating at words such as “vulva” and “spicule” and other anatomical gewgaws of roundworm reproduction. “As a well-brought-up Southern girl,” she says with a laugh, “it's still difficult to talk about this!” © 2013 Nature Publishing Group

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17828 - Posted: 02.20.2013

IF TWO animals have identical brain cells, how different can they really be? Extremely. Two worm species have exactly the same set of neurons, but extensive rewiring allows them to lead completely different lives. Ralf Sommer of the Max Planck Institute for Developmental Biology in Tübingen, Germany, and colleagues compared Caenorhabditis elegans, which eats bacteria, with Pristionchus pacificus, which hunts other worms. Both have a cluster of 20 neurons to control their foregut. Sommer found that the clusters were identical. "These species are separated by 200 to 300 million years, but have the same cells," he says. P. pacificus, however, has denser connections than C. elegans, with neural signals passing through many more cells before reaching the muscles (Cell, doi.org/kbh). This suggests that P. pacificus is performing more complex motor functions, says Detlev Arendt of the European Molecular Biology Laboratory in Heidelberg, Germany. Arendt thinks predators were the first animals to evolve complex brains, to find and catch moving prey. He suggests their brains had flexible wiring, enabling them to swap from plant-eating to hunting. © Copyright Reed Business Information Ltd.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17749 - Posted: 02.04.2013

by Michael Balter CAMBRIDGE, UNITED KINGDOM—Siberia may not be everyone's idea of a tourist destination, but it has been home to humans for tens of thousands of years. Now a new study of indigenous Siberian peoples presented here earlier this month at a meeting on human evolution reveals how natural selection helped people adapt to the frigid north. The findings also show that different living populations adapted in somewhat different ways. Siberia occupies nearly 10% of Earth's land mass, but today it's home to only about 0.5% of the world's population. This is perhaps not surprising, since January temperatures average as low as -25°C. Geneticists have sampled only a few of the region's nearly one dozen indigenous groups; some, such as the 2000-member Teleuts, descendants of a once powerful group of horse and cattle breeders also known for their skill in making leather goods, are in danger of disappearing. Previous research on cold adaptation included two Siberian populations and implicated a couple of related genes. For example, genes called UCP1 and UCP3 tend to be found in more active forms in populations that live in colder climes, according to work published in 2010 by University of Chicago geneticist Anna Di Rienzo and her colleagues. These genes help the body's fat stores directly produce heat rather than producing chemical energy for muscle movements or brain functions, a process called "nonshivering thermogenesis." The new study sampled Siberians much more intensely, including 10 groups that represent nearly all of the region's native populations. © 2010 American Association for the Advancement of Science

Related chapters from BN: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 17730 - Posted: 01.29.2013

Ewen Callaway Even as home experiments go, Hopi Hoekstra’s one was peculiar: she built a giant plywood box in her garage in San Diego, California, filled it with more than a tonne of soil and then let a pet mouse dig away. “This thing was bursting at its seams and held together with duct tape,” says the evolutionary biologist, now at Harvard University in Cambridge, Massachusetts. “But it worked.” It allowed her to study the genetics of burrowing behaviour in a controlled setting. Armed with plastic casts of the burrows and state-of-the-art sequencing, Hoekstra’s team discovered clusters of genes that partly explain why the oldfield mouse (Peromyscus polionotus) builds elaborate two-tunnel burrows, whereas its close relative, the deer mouse (Peromyscus maniculatus), goes for a simple hole in the ground1. The findings highlight an underappreciated benefit of a genomics revolution that is moving at breakneck speed. Thanks to cheap and quick DNA sequencing, scientists interested in the genetics of behaviour need not limit themselves to a handful of favourite lab organisms. Instead, they can probe the genetic underpinnings of behaviours observed in the wild, and glean insights into how they evolved. “In my mind, the link between genes and behaviour in natural populations and organisms is the next great frontier in biology,” says Hoekstra. Oldfield mice are native to the southeastern United States, where they burrow in soils ranging from sandy beaches to silt-rich clays. Wherever they dig, their holes look much the same, with a long entrance tunnel and a second tunnel that stops short of the surface and allows them to escape predators. Such invariability hints that the trait is encoded in DNA, says Hoekstra. © 2013 Nature Publishing Group

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17693 - Posted: 01.17.2013

by Elizabeth Norton To humans, all fire ants may look alike. But the tiny, red, stinging bugs known as Solenopsis invicta have two types of social organization, and these factions are as recognizable to the ants as rival football teams are to us. Researchers once thought that the groups' distinct physiological and behavioral profiles stemmed from a variant in a single gene. Now, a new study provides the first evidence that the gene in question is bound up in a bundle of some 600 other genes, versions of which are all inherited together. This "supergene" takes up a large chunk of what may be the first known social chromosome, analogous to the chromosomes that determine sex in humans. The differences between the two types of fire ants start with the winged queens, according to evolutionary geneticist Laurent Keller of the University of Lausanne in Switzerland. A so-called monogyne queen is large, fat, and fertile. Once she's mated, she can fly long distances to start her colony, nourishing her eggs from her fat stores, and then wait until her larvae grow up into workers. A monogyne colony will accept only the original queen and kill any other that shows up; these ants are very aggressive in general. By contrast, a polygyne queen is smaller and needs mature workers to help set up a colony. Thus polygyne communities will accept multiple queens from nearby nests—unless, that is, one happens to be a monogyne, in which case, they kill her. In 1998, working with entomologist and geneticist Kenneth Ross of the University of Georgia in Athens, Keller showed that the two groups of fire ants had distinct versions of a gene known as Gp-9. All of the monogynes had two copies of one form; among the polygynes, many had one normal and one mutated copy of the gene. At first glance, the finding made sense. © 2010 American Association for the Advancement of Science.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 9: Hearing, Balance, Taste, and Smell
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 6: Hearing, Balance, Taste, and Smell
Link ID: 17691 - Posted: 01.17.2013

By Razib Khan In Slate there is an important piece up, The Early Education Racket, which attempts to reassure upper middle striving types that it isn’t the end of the world if their children don’t get into the right preschool. It is important because there are many people out there with lots of money (or perhaps more accurately, just enough money) and no common sense. Though the author, Melinda Wenner Moyer, offers that she’s not “making a Bell Curve argument here,” the general thesis that there are diminishing returns to inputs on childhood environment is well known to anyone with a familiarity with behavior genetics. Here’s a piece in Psychology Today from 1993, So Long, Superparents: If you are doubtful of this, I recommend you read The Nurture Assumption. This book was published in 1999, and Steve Pinker reported on the results in The Blank Slate a few years later, where I first encountered the thesis. The basic insight, that parental home environment seems to have minimal predictive power in explaining variation in outcomes, is still not very well known. The two primary issues to keep in mind are: 1) A substantial proportion of the variation in I.Q. and personality is heritable in a genetic sense. Many observations of parent-child similarities presumed that they were due to learning and emulation, but statistical analysis suggests this is not the case. Today, with genomic understanding of sibling relatedness (recall that though siblings should be related 0.50, there is some variation about this value) this seems more true than ever; much of the difference between siblings seems to be due to the variation of their genetic make up.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17688 - Posted: 01.17.2013

By Gary Stix The Atlantic featured a captivating fantasy in its November issue about a scenario to assassinate the U.S. president in 2016 by using a bioweapon specifically tailored to his genetic makeup—a virus that targeted the commander in chief and no one else. A great plot for a Hollywood thriller. But will we really see four years from now an engineered pathogen that could home in on just one person’s DNA, a lethal microbe that could be transmitted from person to person by a sneeze? The authors, including “genomic futurist” Andrew Hessel and cybercrime expert Marc Goodman, both faculty at Ray Kurzweil’s Singularity University, acknowledge that the plausibility of a hit on the president by the time of the next election might be reaching a bit. A personal gene bomb monogrammed for Barack Obama is still beyond the technical acumen of the best genetic engineers. But there is one good use beyond the cloaks and daggers to which the president’s genes might eventually be put. As Obama begins his second term next week, he has begun to contemplate his historical legacy. For his third act—that is, once he leaves office—he might consider extending that legacy further by undertaking a whole genome scan. Obama’s genome, as much as that of anyone alive, might help a bit in the long-running search for genes associated with emotional and psychological resilience. Anyone who runs for president and gets the nomination has to display a measure of mental toughness, and so might carry a set of such genes. Romney was a toughie too—recall the first debate—but he was also to the manner born, doing what was expected for someone of his breeding. © 2013 Scientific American

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 11: Emotions, Aggression, and Stress
Link ID: 17684 - Posted: 01.15.2013

By Susan Lunn, CBC News It's the time of year when people take stock of the past 12 months, and make resolutions for the New Year. That's kind of what Svante Paabo is doing — but the Swedish archeological geneticist is looking over a time span of 30,000 years. He's almost finished mapping the DNA of neanderthal man, a distant cousin of modern humans. Paabo has found that many people today carry within their DNA about 3 to 5 per cent in common with neanderthals. Paabo says it's important to learn more about our caveman cousins' DNA to reveal the differences between us and them, differences that have seen modern humans surive and thrive over the millennia, while neanderthals have become extinct. "I really hope that over the next 10 years we will understand much more of those things that set us apart. Which changes in our genome made human culture and technology possible? And allowed us to expand and become 7, 8, 9 billion people and spread all over the world?," he asked at a recent genetic conference in Ottawa. The room was packed with people from across North America who wanted to hear Paabo speak. He's recognized as the inspiration for Michael Crichton's Jurassic Park. © CBC 2012

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17642 - Posted: 12.29.2012

  By Jason G. Goldman In 1976, psychologists John and Sandra Condry of Cornell University had 204 human adults view videotaped footage of an infant boy named David and infant girl named Dana, and asked them to describe the infants’ facial expressions and dispositions. They described their findings in an article in the journal Child Development. In the video, infants were shown responding to various stimuli, which were not visible to the viewer. For example, they’d be shown a teddy bear, so that their reaction could be recorded. They were also videotaped responding to a loud buzzer and to a jack-in-the-box. Participants described David’s response to the jack-in-the-box, for example, as “anger,” while they described Dana’s response to the same toy as “fear.” Participants rated David’s emotional responses to all three stimuli as more “intense” than Dana’s. Here’s the catch: David and Dana were the same infant. Each of the experiment participants were shown the same video of the same infant. Half of them were told the infant was a nine-month-old boy named David, and half were told the infant was a nine-month-old girl named Dana. That they described the “two” infants in such different ways was evidence that the participants’ perceptions were at least based in part upon pre-existing biases and preconceptions about the different ways in which boys and girls experience the world. Now, a group of researchers from Tokyo and Berlin have published a new finding about the relationship between personality and genetics in captive elephants. They collected genetic information from the blood, feces, tissues, cheek swabs, or hair of 196 Asian (Elephas maximus) and African elephants (Loxodonta africana) in Japanese, American, and Canadian zoos, and sanctuaries in Thailand. Personality information was collected for a seventy-five of those elephants by distributing to questionnaires to their keepers. Each elephant was assessed by more than one keeper. An improved understanding of elephant personality would be not only extremely interesting from a basic science perspective, but also extremely useful for more effectively maintaining captive elephant populations in zoos and sanctuaries. The better that zookeepers and curators understand the psychology of the animals in their collections, the better the quality of care can be, which directly impacts animal welfare. © 2012 Scientific American  

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17313 - Posted: 09.29.2012

Nicky Guttridge Subtle differences in the DNA of honeybees are reflected in the bees' roles within the hive. These DNA modifications are normally fixed, but research published today in Nature Neuroscience1 reveals the first example of reversible changes to DNA associated with behaviour. All honeybees (Apis mellifera) are born equal, but this situation doesn’t last long. Although genetically identical, the bees soon take on the specific roles of queen or worker. These roles are defined not just by behavioural differences, but by physical ones. Underlying them are minor modifications to their DNA: ‘epigenetic’ changes that leave the DNA sequence intact, but that add chemical tags in the form of methyl (CH3) molecules to sections of the DNA. This in turn alters the way a gene is expressed2. Once a bee is a queen or worker, they fulfil that role for life — the change is irreversible. But that is not the case for the subdivisions among the workers. The workers start out as nurses, which look after and feed the queen and larvae, and most then go on to become foragers, which travel out from the hive in search of pollen. Again the two types have very different methylation patterns in their DNA. This time, however, as the latest results show, the DNA modifications are reversible: if a forager reverts to being a nurse, its methylation pattern reverts too. © 2012 Nature Publishing Group

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17265 - Posted: 09.17.2012

By Tina Hesman Saey The human genetic instruction book just got more readable. Nearly a decade after the Human Genome Project assembled the genome’s 3 billion chemical units, an international consortium has revealed how the components fit together into sentences and chapters. Already, the genome’s tales are revealing how genetic variants contribute to disease, giving researchers insights into human evolution and even changing how scientists define a gene. “The questions we can now ask are more sophisticated and will yield better answers than the ones we were asking nine years ago,” says Eric Green, director of the National Human Genome Research Institute, which coordinated and funded the mammoth Encyclopedia of DNA Elements, or ENCODE, project. Results from ENCODE, which involves more than 400 researchers around the globe, appear in the Sept. 6 Nature, with more than 30 companion papers published in Science, Genome Research, Genome Biology, Cell and BMC Genetics. When scientists announced the completion of the Human Genome Project in 2003, researchers could pick out genes that carry instructions for building proteins. But that information comprises less than 2 percent of the genome. Some people passed the rest of the genome off as “junk DNA.” © Society for Science & the Public 2000 - 2012

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17230 - Posted: 09.07.2012

By Tina Hesman Saey If variety lends life flavor, then humans are kicking things up to a previously unrecognized notch on the spice-o-meter. New efforts to decipher the genetic blueprints of thousands of people have turned up more than half a million tweaks in human DNA, many more than scientists expected. Most of these tweaks are new to science, and a majority fall into a class called “rare variants,” found in 0.5 percent of the population or less. Some of the variety recently uncovered is so uncommon that it shows up in people living in a single geographic region, or even in only one person. Despite their limited spread, the newly discovered rare variants could profoundly affect susceptibility to disease or how well drugs work. They may also help researchers reconstruct recent human migrations around the world. For years, scientists have been examining the chemical units of DNA called nucleotides that act as letters in the human genetic instruction book. So researchers thought they had a good handle on how often to expect single-letter changes in the A’s, G’s, T’s and C’s in that book. Such changes stem from errors in copying and are spotted via comparison with some majority-rule blueprint. They can go by terms like “single nucleotide polymorphisms” or “mutations” depending on where and when they show up. When looking at 202 genes predicted to be important in diseases from 14,002 people, John Novembre of the University of California, Los Angeles and colleagues unearthed five times as many rare genetic variants as expected. © Society for Science & the Public 2000 - 2012

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 4: Development of the Brain
Link ID: 17149 - Posted: 08.11.2012

By Dan Hurley, New studies are raising the hope of finding a pill to improve the intellectual abilities of people with Down syndrome. One study, published online by the journal Translational Psychiatry, is the first ever to show that a drug might improve the verbal memory of people with the disorder. Although the benefits appeared modest and the study was small, Down syndrome experts meeting last week in Washington called it a major development after more than a decade of research in mice and test tubes. “A lot of us are well aware of progress we’ve seen . . . in the past five to 10 years,” said Jamie Edgin, a developmental psychologist at the University of Arizona in Tucson. Among those advances, she said, are tests designed to measure the cognitive abilities of people with Down syndrome. The development of mice with the genetic equivalent of Down syndrome, essential for studies of possible drug treatments, has been another milestone. “There’s a lot of excitement,” Edgin said. The drug used in the recent study, Namenda, is approved for treating Alzheimer’s disease. Although it has shown only a slim and temporary benefit for that condition, a 2007 study of mice with the genetic equivalent of Down syndrome showed that it almost entirely normalized their ability to learn and remember. The effects in humans appeared far less striking. Alberto Costa, a physician and neuroscientist at the University of Colorado in Denver, ran a test involving 42 young adults with Down syndrome, half of whom received a placebo. After 16 weeks, most of the people who received Namenda performed better on tests of memory than they had at the beginning of the study. But the effect was statistically significant on only one of the 14 tests, which some researchers at last week’s meeting said they considered disappointing. © 1996-2012 The Washington Post

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 4: Development of the Brain
Link ID: 17107 - Posted: 07.31.2012

Daniel H. Geschwind & Genevieve Konopka The decoding of the human and chimpanzee genomes was heralded as an opportunity to truly understand how changes in DNA resulted in the evolution of our cognitive features. However, more than a decade and much detective work later, the functional consequences of such changes have proved elusive, with a few exceptions1, 2. Now, writing in Cell, Dennis et al.3 and Charrier et al.4 describe the evolutionary history and function of the human gene SRGAP2 and provide evidence for molecular and cellular mechanisms that may link the gene's evolution with that of our brain. It was already known that SRGAP2 is involved in brain development5 and that humans have at least three similar copies of the gene, whereas non-human primates carry only one6. However, the study of duplicated, or very similar, segments of DNA is hampered by the fact that most human cells carry two sets of chromosomes (one inherited from each parent), which makes it difficult to distinguish duplicated copies from the different parental forms of the gene. To circumvent this problem, Dennis et al.3 searched for copies of SRGAP2 in the genome of a hydatidiform mole — an abnormal, non-viable human embryo that results from the fusion of a sperm with an egg that has lost its genetic material; it therefore has chromosomes derived from a single parent. The authors showed that humans carry four non-identical copies (named A–D) of SRGAP2 at different locations on chromosome 1. By comparing the genes' sequences with that of the SRGAP2 gene from the orang-utan and chimpanzee, the authors estimated that SRGAP2 was duplicated in the human lineage about 3.4 million years ago, resulting in SRGAP2A (the ancestral version that we share with other primates) and SRGAP2B. Further duplications of SRGAP2B gave rise to SRGAP2C about 2.4 million years ago and to SRGAP2D about 1 million years ago (Fig. 1a). © 2012 Nature Publishing Group

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 0: ; Chapter 4: Development of the Brain
Link ID: 16945 - Posted: 06.21.2012

by Moheb Costandi Researchers have yet to understand how genes influence intelligence, but a new study takes a step in that direction. An international team of scientists has identified a network of genes that may boost performance on IQ tests by building and insulating connections in the brain. Intelligence runs in families, but although scientists have identified about 20 genetic variants associated with intelligence, each accounts for just 1% of the variation in IQ scores. Because the effects of these genes on the brain are so subtle, neurologist Paul Thompson of the University of California, Los Angeles, devised a new large-scale strategy for tackling the problem. In 2009, he co-founded the ENIGMA Network, an international consortium of researchers who combine brain scanning and genetic data to study brain structure and function. Earlier this year, Thompson and his colleagues reported that they had identified genetic variants associated with head size and the volume of the hippocampus, a brain structure that is crucial for learning and memory. One of these variants was also weakly associated with intelligence. Those carrying it scored on average 1.29 points better on IQ tests than others, making it one of the strongest candidate intelligence genes so far. The researchers have now used the same strategy to identify more genetic variants associated with brain structure and IQ. In the new study, they analyzed brain images and whole-genome data from 472 Australians, including 85 pairs of identical twins, 100 pairs of nonidentical twins, and their nontwin siblings. They identified 24 genetic variations within six different genes, all of which were linked to differences in the structural integrity of major brain pathways. © 2010 American Association for the Advancement of Science

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 1: Introduction: Scope and Outlook
Related chapters from MM:Chapter 4: Development of the Brain; Chapter 20:
Link ID: 16942 - Posted: 06.20.2012