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Injury to nerve cells in the brain and spinal cord, once considered permanent, may be reversible after all. A pair of new studies demonstrate how to override two biological mechanisms that prevent damaged cells of the central nervous system from regrowing. The first obstacle are genes that prevent nerve growth and the second are chemical signals that repress nerve growth.

In the first study, published in Science [subscription required], Harvard researchers identified a gene, PETN, that inhibits the major growth pathway in nerve cells. They created genetically modified “knock-out” mice that lacked the gene. Normally, axons in the optic nerve of adult mice do not regenerate when crushed—and worse yet, about 80% of the neurons with severed axons die. But in mice lacking PTEN, 50% of neurons survived and about 10% of axons in the optic nerve regrew—as far as 4 millimeters in 28 days. “To have any manipulation that can make these axons grow from where they were severed near the retina all the way down the optic nerve is just amazing,” [ScienceNOW Daily News] commented neurobiologist Ben Barres.

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Ten intrepid genetic explorers have volunteered to have their genetic information posted on the Internet for anyone’s perusal, along with photographs, their disease histories, allergies, medications, ethnic backgrounds and a trove of other traits, called phenotypes, from food preferences to television viewing habits [The New York Times]. The 10 volunteers are the first participants in the Personal Genomics Project, an endeavor run by Harvard Medical School that hopes to offer free genetic testing to 100,000 people in exchange for their privacy.

The project aims to advance genome research by tapping volunteers who have a Facebook-mentality sense of privacy–minimal–and enough excitement about genomic science that they are willing to lay out their genetic and medical information so any researcher can sift through it for links between genes and traits. “There’s a hope that by making these data public, you can harness crowd-sourcing power in the same way that Wikipedia and YouTube and Google and Linux all emerged from cooperative, distributed efforts” [Boston Globe], said Harvard psychology professor Steven Pinker, who is one of the 10 pioneers.

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In a counterintuitive new study, researchers have found that obese women get less pleasure from drinking a chocolate milkshake than average-weight women, and suggest that obese women are therefore more likely to overeat in an attempt to get that high. Researchers used a fMRI brain scanner to record women’s levels of the pleasure-providing brain chemical dopamine while they were sipping milkshakes, and found that obese women had a muted pleasure response.

They also studied a dopamine-regulating gene variant that has previously been linked to obesity, and showed that women with this variant had the lowest dopamine levels and were also very likely to gain weight over the ensuing year. Dopamine expert Nora Volkow says this furthers the research on the genetic component of obesity: “It takes the gene associated with greater vulnerability for obesity and asks the question why. What is it doing to the way the brain is functioning that would make a person more vulnerable to compulsively eat food and become obese?” [AP]

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Two separate groups of researchers have developed a non-invasive test for Down syndrome, using only a blood sample from the pregnant woman to examine the fetus’ DNA. While the genetic tests are still in clinical trials, experts are hailing the achievement as significant because current prenatal tests like amniocentesis require inserting a needle in the uterus, and carry a risk of miscarriage.

A biotechnology company called Sequenom says it will begin selling its test next June, while researchers from Stanford, who just published their results in the Proceedings of the National Academy of Sciences, are still planning a large-scale clinical trial. Some experts say that the results are somewhat preliminary, and should be viewed cautiously: The Stanford test has been tried on only 18 blood samples. Sequenom has tried its test on only about 400 samples and has not yet published its results in peer-reviewed journals. Still, both tests have perfect records so far: no false negatives or false positives. “This is quite simply a major step forward, if it works at all like we expect it might,” [says Down Syndrome expert] Jacob A. Canick [The New York Times].

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A biotechnology company has announced a new price for sequencing an individual’s entire genome: $5,000. The announcement from the California start-up Complete Genomics signifies a drastic price drop–the going rate for a complete genome is currently about $100,000–and could allow researchers to routinely collect vast amounts of genetic information. Researchers say that a $5,000 genome would enable new studies to identify rare genetic variants linked to common diseases, and it could open up the sequencing market to diagnostic and pharmaceutical companies, making genome sequencing a routine part of clinical drug testing [ABC News].

Complete Genomics won’t offer its services directly to people who are curious about their genetic makeup, setting it apart from consumer-oriented companies like 23andMe and deCODE Genetics. Complete Genomics expects most of its customers to be pharmaceutical companies or research laboratories that are doing studies aimed at finding genes linked to diseases. Such studies might look at the DNA of 1,000 people with a disease and 1,000 people without the disease. Right now, such studies look at only particular locations in the DNA because it is too expensive to determine the entire DNA sequence. But presumably, an entire sequence would provide more complete information [The New York Times].

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Researchers have found a way to create stem cells from adult liver cells without triggering DNA changes that have caused mutations and tumors in previous studies. Though demonstrated only in mice so far, the result marks another key achievement in the fledgling science of cellular reprogramming. The hope is to create human, embryonic-like stem cells — which can be turned into all the other tissue types of the body — without using eggs or destroying embryos. That freshly derived tissue could then be transplanted into patients to treat various diseases [The Wall Street Journal].

A method of using adult cells to create stem cells was debuted by Japanese researchers in 2006. By using viruses to insert key developmental genes, researchers coaxed human skin cells into an embryonic state, capable of growing into almost any other type of tissue…. But there was a catch: Viruses used to reset the cells tended to fuse with their DNA, leading to unpredictable mutations and cancer. The cells were promising in principle, but couldn’t be used medically [Wired News]. In the new breakthrough, researchers used a different kind of virus to introduce the genes, and found that it didn’t leave behind any damaging genetic code.

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A new method to identify an individual’s genetic profile from a larger pool of genetic data could be a boon for forensic science, but is causing headaches for the National Institutes of Health. In response to a study describing the technique, the NIH quickly removed several publicly available databases of DNA information drawn from medical studies, citing concerns that patients’ privacy could be threatened.

The new type of DNA analysis could only identify an individual if that person’s genetic profile was already known. Such a confirmation could reveal patients’ participation in a study about a specific medical condition, denying them their presumed confidentiality, experts said [Los Angeles Times]. NIH officials say they took down the databases, which contained genetic data from more than 60,000 patients, as a precautionary measure, and say it’s unlikely that the privacy of any of those patients has been violated.

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Scientists have produced the cells that make up delicate inner ear hairs in mouse embryos, a step that could point the way to reversing hearing loss and curing congenital deafness. Sensory hair cells inside the cochlea, the auditory portion of the inner ear, convert sound waves into electrical impulses that are delivered to the brain. The loss of these minute hairs, or the nerves that control them, is the most common cause of hearing impairment and so-called nerve deafness [ABC Science].

Researchers used gene therapy to create the crucial cells: They used a virus to introduce a gene into the mice embryos, which caused non-sensory cells to turn into cochlear hair cells. While this preliminary experiment was done on normal-hearing mice, the discovery that the engineered cochlear cells functioned as well as natural cells was an important step. Says lead researcher John Brigande: “One approach to restore auditory function is to replace defective cells with healthy new cells…. Our work shows that it is possible to produce functional auditory hair cells in the mammalian cochlea” [Reuters].

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The trick to keeping organs working well into old age might be taking out the trash, according to a study in Nature Medicine [subscription required]. Researchers led by Ana Maria Cuervo of Yeshiva University in New York have slowed the aging process in the livers of mice by tinkering with a system that recycles the damaged proteins hanging around in a cell.

Molecules responsible for “chaperone-mediated autophagy“ handle about 30 percent of the cells’ damaged proteins, escorting them to inner cell structures called lysosomes, where enzymes break the proteins down. Studies by Cuervo have shown that the disposal system becomes less efficient as cells grow older. They’ve also pinpointed the reason for the age-related decline — a loss of receptors on the surface of the lysosomes that causes a buildup of damaged proteins in the cell [U.S. News & World Report].

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In a striking achievement, researchers have taken ordinary skin cells from two elderly women suffering from Lou Gehrig’s disease, also known as amyotrophic lateral sclerosis, and have reprogrammed those cells to act like stem cells, the versatile cells that can grow into almost any kind of specialized cell. Then the researchers programmed the cells to turn into motor neurons, the type of nerve cells that waste away and die as ALS progresses.

The new nerve cells won’t be used in any sort of experimental treatment; instead researchers will look for flaws in these nerve cells to study the disease’s mechanism. “Now we can make limitless supplies of the cells that die in this awful disease. This will allow us to study these neurons, and ALS, in a lab dish, and figure out what’s happening in the disease process,” said [study coauthor] Dr. Kevin Eggan [Reuters]. This is particularly useful for ALS because the nerve cells affected by the disease are in patients’ spinal cords, making it impossible for researchers to take cell samples for study.

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Two large, international studies have independently found three genetic mutations that are linked to a greatly increased risk of schizophrenia, but say the rare mutations only account for a small percentage of schizophrenia cases. The identification of the three mutations is being hailed as a breakthrough, as no genetic factors had been definitively linked to the disease before. But in a finding of even greater importance, the studies suggest that there’s no easy answer to the question of what causes the devastating mental illness. Instead of a common genetic problem, schizophrenia may be triggered by many rare mutations that cause subtly different variants of the disease.

“What is beginning to emerge is that a lot of the risk of brain diseases is conferred by rare [genetic] deletions,” [study author Kari] Stefansson said…. The new focus on rare mutations suggests that natural selection is highly efficient at removing schizophrenia-causing genes from the population. Despite selection against the disease, according to this new idea, schizophrenia continues to appear because it is driven by a spate of new mutations that occur all the time in the population. [The New York Times].

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Victor McKusick, the visionary researcher who is often called the father of medical genetics, died on Tuesday at the age of 86, from complications from cancer. “Today we have lost a giant,” said Johns Hopkins Medicine dean… Edward D. Miller. “He spent virtually all of his incredible career at Hopkins, but his influence and legacy reach around the world” [AP].

McKusick began his career as a cardiologist, but in the early 1950s he shifted focus. While examining a patient with Peutz-Jeghers syndrome, a rare inherited disease that puts patients at high risk of developing intestinal cancer and causes odd skin pigmentation, Dr. McKusick became curious about how a single genetic mutation led to problems in various organs…. In the late 1950s, just a few years after DNA was discovered, he decided to devote his career to medical genetics [Baltimore Sun].

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It’s a mind-boggling piece of medical news: A genetic variant that’s commonly found in people of African descent raises the risk of HIV infection by about 40 percent, but also causes HIV-infected people to live longer. Researchers say the trait is extremely common because it used to have a beneficial effect; it protected people against a form of malaria that is now fairly rare.

The genetic variant may partially account for the high HIV rates in sub-Saharan Africa, where over 24 million people are currently living with the disease. While the differences in HIV prevalence in different parts of the world can be partly explained by different social conditions and sexual behaviour, scientists have long suspected that there may be genetic reasons why the virus is rife in certain communities [BBC News].

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Researchers say they turned a mouse with muscular dystrophy into a mighty mouse by injecting stem cells into its muscles. Just a few weeks after injecting the stem cells, which were taken from the muscles of healthy adult mice, the weak and wasting muscles of the ailing mice were almost completely restored to full strength.

While human trials are still years away, the results offer hope that one day skeletal muscle stem cells from healthy people could be grafted into those with muscle disorders, says Amy Wagers, coauthor of the paper…. People with other kinds of muscle damage could benefit as well, she says. “There are a lot of situations where muscle is degenerating or damaged and you might want to boost its regenerative capacity” [Science News]. 

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Researchers have discovered five new genetic defects that are linked to autism and that appear to share a common function: They’re associated with learning, and are part of a network that allows a child’s brain to build new connections in response to experience [Web MD].

Symptoms of autism typically emerge during the first five years of life — a period when a child normally picks up language, social skills and many other new abilities. Scientists call this kind of growth “experience-dependent learning,” and researchers know that it is associated with enormous changes in brain circuitry. At least 300 genes switch on and off to regulate experience-dependent learning [Time]. Researchers say that the newly identified genes, as well as others already linked to autism, may fail to turn on during this crucial developmental stage, preventing children from learning those social skills and abilities.

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