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Archive - Mar 2014

Date

March 24th

Sea Anemone Shows Characteristics of Both Plant and Animal in Gene Regulation

A team led by evolutionary and developmental biologist Dr. Ulrich Technau at the University of Vienna has discovered that sea anemones display a genomic landscape with a complexity of regulatory elements similar to that of fruit flies or other animal model systems. This suggests, that this principle of gene regulation is already 600 million years old and dates back to the common ancestor of human, fly, and sea anemone. On the other hand, sea anemones are more similar to plants rather thn to vertebrates or insects in their regulation of gene expression by short regulatory RNAs called microRNAs. These surprising evolutionary findings were published on March 18, 2014 in two open-access articles in Genome Research. Our appearance, the shape we have and how our body works is, in addition to environmental influences, largely the result of the action of our genes. However, genes are rarely single players, they rather act in concert and regulate each other's activity and expression in gene regulatory networks. In the last decades, the sequencing of the human and many animal genomes has shown that anatomically simple organisms such as sea anemones have a surprisingly complex gene repertoire similar to that of higher model organisms. This implies, that the difference in morphological complexity cannot be easily explained by the presence or absence of individual genes. Some researchers hypothesized that the individual genes do not code for more complex body plans, but that this is determined by how the genes are wired and linked between each other. Accordingly, researchers expected that these gene networks are less complex in simple organisms than in human or "higher" animals. A measurement of the complexity of gene regulation could be the distribution and density of regulatory sequences in the genome.

Scientists Identify Gene That May Influence the Timing of Puberty

Scientists have identified a gene that may influence the timing of puberty, according to research presented on Mrch 25, 2014 at the Society for Endocrinology annual BES conference in Liverpool, United Kingdom. Until now, very little has been known about the genetic control of puberty. More than 4% of adolescents suffer from early or late-onset puberty, which is associated with health problems including obesity, type-2 diabetes, cardiovascular disease, and cancer. The findings of the study are expected to make diagnosis easier and more efficient, reducing the risk of disease. Researchers from Queen Mary University of London scanned the genomes of seven families experiencing delayed puberty. The genetic profiles were analyzed to identify specific genes that were different in these families, compared to individuals who started puberty normally. The researchers identified 15 candidate genes that were then examined in a further 288 individuals with late-onset puberty. One gene was found to have common variants in nine families. The gene appears to contribute to the early development of gonadotropin-releasing hormone (GnRH) neurons in the brain. At puberty, a surge of GnRH is released, signaling to the pituitary gland to release further hormones that act on the ovaries and testes, triggering reproductive function (sexual maturation). If development of the GnRH neurons is delayed, the surge of GnRH that initiates these signals is also delayed. Dr. Sasha Howard, who led the study, said, “Studies estimate that 60-80% of variation in the timing of puberty is genetically determined, yet this is one of the first genes with major impact to be identified.

March 17th

China Halves Tuberculosis Prevalence in Just 20 Years

Over the last 20 years, China has more than halved its tuberculosis (TB) prevalence, with rates falling from 170 to 59 per 100 000 population. This unrivalled success has been driven by a massive scale-up of the directly observed, short-course (DOTS) strategy, from half the population in the 1990s to the entire country after 2000, according to findings from a 20-year-long analysis of national survey data, published online on March 18, 2014 in The Lancet. "One of the key global TB targets set by the Stop TB Partnership aims to reduce tuberculosis prevalence by 50% between 1990 and 2015. This study in China is the first to show the feasibility of achieving such a target, and China achieved this 5 years earlier than the target date," says study leader Dr. Yu Wang from the Chinese Center for Disease Control and Prevention in Beijing, China. "Huge improvements in TB treatment, driven by a major shift in treatment from hospitals to local public health centers implementing the DOTS strategy, were largely responsible for this success." China is a major contributor to the TB pandemic, with 1 million new TB cases every year, accounting for 11% of all new cases globally. Two national surveys of tuberculosis prevalence in 1990 and 2000 showed that levels of TB were reduced by around 30% in the 13 provinces where the DOTS program was adopted. However, national TB prevalence fell by just 19% over the decade. Another survey was done in 2010 to re-evaluate the national TB burden, providing an opportunity to assess the effect of the nationwide expansion of the DOTS program. Nearly 253,000 individuals aged 15 years and older were surveyed in 2010 at 176 investigation points chosen from all 31 mainland provinces. The results showed that between 2000 and 2010, national TB prevalence fell by 57%—tripling the reduction of the previous decade.

Antarctic Moss Comes Back to Life after 1,500 Years under Ice

Researchers from the British Antarctic Survey and the University of Reading reported online in the Cell Press journal Current Biology on March 17, 2014 that Antarctic mosses can essentially come back to life after 1,500 completely inactive years under the ice. Prior to this finding, direct regeneration from frozen plant material had been demonstrated after 20 years at most. Beyond that, only microbes had been shown to be capable of revival after so many years on hold. "These mosses were basically in a very long-term deep freeze," says Dr. Peter Convey of the British Antarctic Survey. "This timescale of survival and recovery is much, much longer than anything reported for them before." The findings in mosses have special relevance for Antarctic ecosystems and climate, Dr. Convey adds, because mosses are primary producers on land in both northern and southern polar regions. In the north in particular, mosses are responsible for storing most of the fixed carbon. If mosses can survive in this way for such long periods of time, then regrowth once the ice retreats wouldn't require long-distance, transoceanic colonization events. Dr. Convey and his colleagues primarily study polar moss cores because they provide a novel archive of past climate conditions. The researchers use them to assess growth rates over time and as proxies to reconstruct aspects of the environment and environmental change over time. The oldest moss banks of the type under study in the Antarctic date back 5,000 to 6,000 years. The one the researchers focused on in the current work is nearly 2,000 years old at its base. In the beginning, the researchers weren't sure that mosses frozen for more than a decade or two would remain viable. When they began to see the 1,500-year-old mosses start to regrow, it came as a real surprise.

Sequencing Reveals Genetic Diversity in Hospital-Acquired, Antibiotic-Resistant Klebsiella

Using genome sequencing, National Institutes of Health (NIH) scientists and their colleagues have tracked the evolution of the antibiotic-resistant bacterium Klebsiella pneumoniae sequence type 258 (ST258), an important agent of hospital-acquired infections. While researchers had previously thought that ST258 K. pneumoniae strains spread from a single ancestor, the NIH team showed that the strains arose from at least two different lineages. The investigators also found that the key difference between the two groups lies in the genes involved in production of the bacterium's outer coat, the primary region that interacts with the human immune system. Their results, which appeared online on March 17, 2014 in PNAS, promise to help guide the development of new strategies to diagnose, prevent. and treat this emerging public health threat. ST258 K. pneumoniae is the predominant cause of human infections among bacteria classified as carbapenem-resistant Enterobacteriaceae (CRE), which kill approximately 600 people annually in the United States and sicken thousands more. Most CRE infections occur in hospitals and long-term care facilities among patients who are already weakened by unrelated disease or have undergone certain medical procedures. In the new study, scientists from the NIH's National Institute of Allergy and Infectious Diseases (NIAID) and their colleagues sequenced the complete genomes of ST258 K. pneumoniae strains collected from two patients in New Jersey hospitals. By comparing these reference genomes with gene sequences from an additional 83 clinical ST258 K. pneumoniae isolates, the scientists found that the strains divided broadly into two distinct groups, each with its own evolutionary history.

March 16th

Colon Cancer Incidence Rates Dropping Steeply in Older Americans; Growing Use of Colonoscopy Credited

Colon cancer incidence rates have dropped 30 percent in the U.S. in the last 10 years among adults 50 and older due to the widespread uptake of colonoscopy, with the largest decrease in people over age 65. Colonoscopy use has almost tripled among adults ages 50 to 75, from 19 percent in 2000 to 55 percent in 2010. The findings come from Colorectal Cancer Statistics, 2014, published online on March 17, 2014 in CA: A Cancer Journal for Clinicians. The article and its companion report, Colorectal Cancer Facts & Figures, were released today by American Cancer Society researchers as part of a new initiative by the National Colorectal Cancer Roundtable to increase screening rates to 80 percent by 2018. Colorectal cancer, commonly called colon cancer, is the third most common cancer and the third leading cause of cancer death in men and women in the United States. Its slow growth from precancerous polyp to invasive cancer provides a rare opportunity to prevent cancer through the detection and removal of precancerous growths. Screening also allows early detection of cancer, when treatment is more successful. As a result, screening reduces colorectal cancer mortality both by decreasing the incidence of disease and by increasing the likelihood of survival. Using incidence data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program and the Centers for Disease Control and Prevention's National Program of Cancer Registries, as provided by the North American Association of Central Cancer Registries (NAACCR), researchers led by Rebecca Siegel, M.P.H., found that during the most recent decade of data (2001 to 2010), overall incidence rates decreased by an average of 3.4 percent per year. However, trends vary substantially by age.

Plant Nanobionics Augments Photosynthesis and Biochemical Sensing

Plants have many valuable functions: They provide food and fuel, release the oxygen that we breathe, and add beauty to our surroundings. Now, a team of MIT researchers, with collaborators at Cal Tech and Dumlupinar University in Turkey, wants to make plants even more useful by augmenting them with nanomaterials that could enhance their energy production and give them completely new functions, such as monitoring environmental pollutants. In a new Nature Materials paper, published online on March 16, 2014, the researchers report boosting plants' ability to capture light energy by 30 percent by embedding carbon nanotubes in the chloroplast, the plant organelle where photosynthesis takes place. Using another type of carbon nanotube, they also modified plants to detect the gas nitric oxide. Together, these represent the first steps in launching a scientific field the researchers have dubbed "plant nanobionics." "Plants are very attractive as a technology platform," says Dr. Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering and leader of the MIT research team. "They repair themselves, they're environmentally stable outside, they survive in harsh environments, and they provide their own power source and water distribution." Dr. Strano and the paper's lead author, postdoc and plant biologist Dr. Juan Pablo Giraldo, envision turning plants into self-powered, photonic devices such as detectors for explosives or chemical weapons. The researchers are also working on incorporating electronic devices into plants. "The potential is really endless," Dr. Strano says. The idea for nanobionic plants grew out of a project in Strano's lab to build self-repairing solar cells modeled on plant cells.

March 16th

Novel Approach Reveals Gene Variant That Reduces Heart Attack Risk

Scientists have discovered a previously unrecognized gene variation that makes humans have healthier blood lipid levels and reduced risk of heart attacks -- a finding that opens the door to using this knowledge in testing or treatment of high cholesterol and other lipid disorders. But even more significant is how they found the gene, which had been hiding in plain sight in previous hunts for genes that influence cardiovascular risk. This region of DNA where the gene was found had been implicated as being important in controlling blood lipid levels in a report from several members of the same research team in 2008. But although this DNA region had many genes, none of them had any obvious link to blood lipid levels. The promise of an entirely new lipid-related gene took another six years and a new approach to find. In a new paper published online on March 16, 2014 in Nature Genetics, a team from the University of Michigan (U-M) and the Norwegian University of Science and Technology reports that they have zeroed in on the gene in an entirely new way. The team scanned the genetic information available from a biobank of thousands of Norwegians, focusing on variations in genes that change the way proteins function. Most of what they found turned out to be already known to affect cholesterol levels and other blood lipids. But one gene, named TM6SF2, wasn't on the radar at all. In a minority of the Norwegians who carried a particular change in the gene, blood lipid levels were much healthier and they had a lower rate of heart attacks. And when the researchers boosted or suppressed the gene in mice, they saw the same effect on the animals' blood lipid levels.

Scientists Clarify Mechanisms of Nectar Production and Secretion

Evolution is based on diversity, and sexual reproduction is key to creating a diverse population that secures competitiveness in nature. Plants had to solve a problem: they needed to find ways to spread their genetic material. Flying pollinators—insects, birds, and bats—were nature's solution. Charles Darwin's "abominable mystery" highlighted the coincidence of flowering plant and insect diversification about 120 million years ago and ascribed it to the coordinated specialization of flowers and insects in the context of insects serving as pollen carriers. To make sure the flying pollinators would come to the flowers to pick up pollen, plants evolved special organs called nectaries to attract and reward the animals. These nectaries are secretory organs that produce perfumes and sugary rewards. Yet despite the obvious importance of nectar, the process by which plants manufacture and secrete it has largely remained a mystery. New research from a team led by the Carnegie Institute of Science’s (Washinton, D.C.) Dr. Wolf Frommer, director of the Plant Biology Department, in collaboration with the Carter lab in Minnesota and the Baldwin lab in Jena, Germany, has now identified key components of the sugar synthesis and secretion mechanisms. Their work also suggests that the components were recruited for this purpose early during the evolution of flowering plants. Their work was published online on March 16, 2014 in Nature. The team used advanced techniques to search for transporters that could be involved in sugar transport and were present in nectaries. They identified the transport protein SWEET9 as a key player in three diverse flowering plant species and demonstrated that it is essential for nectar production.

MicroRNAs Target Transposons in Plant Reproductive Cells, Protecting Against Genome Damage

Reproductive cells, such as an egg and sperm, join to form stem cells that can mature into any tissue type. But how do reproductive cells arise? We humans are born with all of the reproductive cells that we will ever produce. But in plants things are very different. They first generate mature, adult cells and only later "reprogram" some of them to produce eggs and sperm. For a plant to create reproductive cells, it must first erase a key code, a series of tags attached to DNA across the genome known as epigenetic marks. These marks distinguish active and inactive genes. But the marks serve another critical role. They keep a host of damaging transposons, or "jumping genes," inactive. As the cell wipes away the epigenetic code, it activates transposons, placing the newly formed reproductive cell in great danger of sustaining genetic damage. On March 16, 2014, researchers at Cold Spring Harbor Laboratory (CSHL) in New York led by Professor and HHMI Investigator Dr. Robert Martienssen announce the discovery of a pathway that helps to keep transposons inactive even when the epigenetic code is erased. "Jumping genes" were first identified more than 50 years ago at CSHL by Nobel-prize-winning researcher Dr. Barbara McClintock. Subsequent study revealed that jumping genes (or transposable elements) are long, repetitive stretches of DNA. They resemble remnants of ancient viruses that have inserted themselves into their host DNA. When active, transposons copy themselves and jump around in the genome. They can insert themselves right in the middle of genes, thus interrupting them. Scientists have found that more than 50% of the human genome is made up of transposons. Remarkably, in plants, up to 90% of the genome is composed of these repetitive sequences.