Biophysicists Measure Mechanism That Determines Fate of Living Cells

A new tension gauge tether (TGT) laboratory method developed at the University of Illinois at Urbana-Champaign has broad applications for research into stem cells, cancer, infectious disease, and immunology.

In this experiment, ligand molecules are tethered by DNA strands to a substrate; the strands have defined tension tolerances and will burst if tension above their tolerance is applied. The integrin-ligand bond activates cellular adhesion only when the tether does not rupture, enabling a measurement to be taken of the molecular force. The cultures show cell adhesion and spreading at a tension tolerance of 43 pico-Newtons but not at 33 pico-Newtons. (Credit: Image courtesy of University of Illinois College of Engineering)

Cells in the human body do not function in isolation. Living cells rely on communication with their environment -- neighboring cells and the surrounding matrix -- to activate a wide range of cellular functions, including reproduction of new cells, differentiation of stem cells into distinct cell types, cell adhesion, and migration of white blood cells to fight bodily infections. This cellular communication occurs on the molecular level and it is reciprocal: a cell receives cues from and also transmits function-activating cues to its neighbors.

The mechanics of this type of cellular interaction have been studied extensively: receptors extending through the cell membrane are activated when they form a bond to specific molecules. Now for the first time, University of Illinois biophysicists at the Center for the Physics of Living Cells and the Institute for Genomic Biology have measured the molecular force required to mechanically transmit function-regulating signals within a cell.

The new laboratory method, named the tension gauge tether (TGT) approach, developed by Taekjip Ha with postdoctoral researcher Xuefeng Wang, and reported in the May 24, 2013, issue of the journal Science, has made it possible to detect and measure the mechanics of the single-molecule interaction by which human cell receptors are activated. The researchers used integrin, a cell membrane receptor protein that is activated when it bonds to a ligand molecule.

In the TGT approach, Ha and Wang repurposed DNA strands, using them as tethers for ligand molecules, to test the tension required to activate cell adhesion through integrin. The integrin bonds to the tethered ligand, and adhesion is activated only if the DNA tether does not rupture.

Taking advantage of the geometric characteristics of DNA's double helix form, the researchers were able to tune the strands to rupture at discrete tension levels: by varying the attachment points along the DNA strands, the force required for rupture was either low (unzipping the helix), high (shearing the strands), or intermediary (combination of unzipping and shearing).

"If you went fishing and a fish broke your 30-lb fishing line but not the 40-lb one, you would know that its strength was in the range of 30­-40 pounds," explained Wang. "Here we applied the same strategy to measure the molecular tension applied by cells (the fish). Mammalian cells apply a force to activate cell membrane proteins called integrins which mediate cell adhesion. We immobilized ligand molecules (the bait) on a surface through molecular tethers (the fishing line) with defined tension tolerances, tunable from 10 pico Newton (pN) to 60 pN). After integrin-ligand binding, cells apply a force on the bonds, and we compare this force to the molecular tether strength by observing cell adhesion status."

Since single-molecule interactions are difficult to monitor, the researchers observed the receptor-regulated cellular function, to gauge whether the integrin was activated. Ha and Wang discovered that integrin experiences a well-defined "quantum of force," about 40 pico-Newton (pN), to activate cell's adhesion to a surface.

"We observed that mammalian cells adhere on the culture surface with 43 pN tension tolerance of ligands, but not on 33 pN surface. Therefore we deduced that single molecular tension is around 40 pN on integrin cell-membrane receptors during cell adhesion," Wang added.

"This is a very exciting result," commented Ha, an Edward William and Jane Marr Gutgsell Endowed Professor at Illinois. "With the ability to define the single molecular forces required to make living cells behave as desired, we may be one step closer to a remedy for certain hard-to-cure diseases. We know that the behavior of cancer cells and stem cells can be controlled by how stiff or soft their environments are. Understanding and manipulating molecular conversation through defined forces has huge implications for the development of future medical interventions. We expect the TGT approach will have broad applications in laboratory studies of cell differentiation, cancer metastasis, as well as immunology and infectious disease."

This research was funded by the National Science Foundation through the Physics Frontiers Center Program (0822613). In addition to his appointment at the University of Illinois, Taekjip Ha is an investigator with the Howard Hughes Medical Institute.

Journal Reference:

1. X. Wang, T. Ha. Defining Single Molecular Forces Required to Activate Integrin and Notch Signaling.Science, 2013; 340 (6135): 991 DOI:10.1126/science.1231041

Courtesy: ScienceDaily

Molecule That Triggers Sensation of Itch Discovered

Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as the sensation of itch.

The small molecule, called natriuretic polypeptide b (Nppb), streams ahead and selectively plugs into a specific nerve cell in the spinal cord, which sends the signal onward through the central nervous system. When Nppb or its nerve cell was removed, mice stopped scratching at a broad array of itch-inducing substances. The signal wasn't going through.

Because the nervous systems of mice and humans are similar, the scientists say a comparable biocircuit for itch likely is present in people. If correct, this start switch would provide a natural place to look for unique molecules that can be targeted with drugs to turn off the sensation more efficiently in the millions of people with chronic itch conditions, such eczema and psoriasis.

The paper, published online in the journal Science, also helps to solve a lingering scientific issue. "Our work shows that itch, once thought to be a low-level form of pain, is a distinct sensation that is uniquely hardwired into the nervous system with the biochemical equivalent of its own dedicated land line to the brain," said Mark Hoon, Ph.D., the senior author on the paper and a scientist at the National Institute of Dental and Craniofacial Research, part of the National Institutes of Health.

Hoon said his group's findings began with searching for the signaling components on a class of nerve cells, or neurons, that contain a molecule called TRPV1. These neurons, with their long nerve fibers extending into the skin, muscle, and other tissues, help to monitor a range of external conditions, from extreme temperature changes to detecting pain.

Yet little is known about how these neurons recognize the various sensory inputs and, like sorting mail, know how to route them correctly to the appropriate pathway to the brain.

To fill in more of the details, Hoon said his laboratory identified in mice some of the main neurotransmitters that TRPV1 neurons produce. A neurotransmitter is a small molecule that neurons selectively release when stimulated, like a quick pulse of water from a faucet, to communicate sensory signals to other nerve cells.

The scientists screened the various neurotransmitters, including Nppb, to see which ones corresponded with transmitting sensation.

"We tested Nppb for its possible role in various sensations without success," said Santosh Mishra, lead author on the study and a researcher in the Hoon laboratory. "When we exposed the Nppb-deficient mice to several itch-inducing substances, it was amazing to watch. Nothing happened. The mice wouldn't scratch."

Further experiments established that Nppb was essential to initiate the sensation of itch, known clinically as pruritus. Equally significant, the molecule was necessary to respond to a broad spectrum of pruritic substances. Previous research had suggested that a common start switch for itch would be unlikely, given the myriad proteins and cell types that seemed to be involved in processing the sensation.

Hoon and Mishra turned to the dorsal horn, a junction point in the spine where sensory signals from the body's periphery are routed onward to the brain. Within this nexus of nerve connections, they looked for cells that expressed the receptor to receive the incoming Nppb molecules.

"The receptors were exactly in the right place in the dorsal horn," said Hoon, the receptor being the long-recognized protein Npra. "We went further and removed the Npra neurons from the spinal cord. We wanted to see if their removal would short-circuit the itch, and it did."

Hoon said this experiment added another key piece of information. Removing the receptor neurons had no impact on other sensory sensations, such as temperature, pain, and touch. This told them that the connection forms a dedicated biocircuit to the brain that conveys the sensation of itch.

But the scientists had stepped into a conundrum. Previous reports had suggested that another neurotransmitter called GRP might initiate itch. If that wasn't the case, where did GRP fit into the process?

They tested the receptor neurons that express GRP, finding the previous reports were correct about this molecule relaying the signal to the central nervous system. GRP just enters the picture after Nppb already has set the sensation in motion.

Based on these findings, Nppb would seem to be an obvious first target to control itch. But that's not necessarily the case. Nppb also is used in the heart, kidneys, and other parts of the body, so attempts to control the neurotransmitter in the spine has the potential to cause unwanted side effects.

"The larger scientific point remains," said Hoon. "We have defined in the mouse the primary itch-initiating neurons and figured out the first three steps in the pruritic pathway. Now the challenge is to find similar biocircuitry in people, evaluate what's there, and identify unique molecules that can be targeted to turn off chronic itch without causing unwanted side effects. So, this is a start, not a finish."

Journal Reference:

1. S. K. Mishra, M. A. Hoon. The Cells and Circuitry for Itch Responses in Mice. Science, 2013; 340 (6135): 968 DOI:10.1126/science.1233765

Courtesy: ScienceDaily

Advanced Biological Computer Developed

cientists at the Technion-Israel Institute of Technology have developed and constructed an advanced biological transducer, a computing machine capable of manipulating genetic codes, and using the output as new input for subsequent computations. The breakthrough might someday create new possibilities in biotechnology, including individual gene therapy and cloning.

The findings appear on May 23, 2013 in Chemistry & Biology (Cell Press).

Interest in such biomolecular computing devices is strong, mainly because of their ability (unlike electronic computers) to interact directly with biological systems and even living organisms. No interface is required since all components of molecular computers, including hardware, software, input and output, are molecules that interact in solution along a cascade of programmable chemical events.

"Our results show a novel, synthetic designed computing machine that computes iteratively and produces biologically relevant results," says lead researcher Prof. Ehud Keinan of the Technion Schulich Faculty of Chemistry. "In addition to enhanced computation power, this DNA-based transducer offers multiple benefits, including the ability to read and transform genetic information, miniaturization to the molecular scale, and the aptitude to produce computational results that interact directly with living organisms."

The transducer could be used on genetic material to evaluate and detect specific sequences, and to alter and algorithmically process genetic code. Similar devices, says Prof. Keinan, could be applied for other computational problems.

"All biological systems, and even entire living organisms, are natural molecular computers. Every one of us is a biomolecular computer, that is, a machine in which all components are molecules "talking" to one another in a logical manner. The hardware and software are complex biological molecules that activate one another to carry out some predetermined chemical tasks. The input is a molecule that undergoes specific, programmed changes, following a specific set of rules (software) and the output of this chemical computation process is another well defined molecule."

Also contributing to the research were postdoctoral fellows Dr. Tamar Ratner and Dr. Ron Piran of the Technion's Schulich Faculty of Chemistry, and Dr. Natasha Jonoska of the Department of Mathematics at the University of South Florida.

Journal Reference:

1. Tamar Ratner, Ron Piran, Natasha Jonoska, Ehud Keinan.Biologically Relevant Molecular Transducer with Increased Computing Power and Iterative Abilities.Chemistry & Biology, 2013; 20 (5): 726 DOI:10.1016/j.chembiol.2013.02.016

Courtesy: Science Daily

H1N1 Discovered in Marine Mammals

Scientists at the University of California, Davis, detected the H1N1 (2009) virus in free-ranging northern elephant seals off the central California coast a year after the human pandemic began, according to a study published today, May 15, in the journal PLOS ONE. It is the first report of that flu strain in any marine mammal.

"We thought we might find influenza viruses, which have been found before in marine mammals, but we did not expect to find pandemic H1N1," said lead author Tracey Goldstein, an associate professor with the UC Davis One Health Institute and Wildlife Health Center. "This shows influenza viruses can move among species."

UC Davis researchers have been studying flu viruses in wild birds and mammals since 2007 as part of the Centers of Excellence in Influenza Research and Surveillance program funded by National Institutes of Health. The goal of this research is to understand how viruses emerge and move among animals and people.

Between 2009 and 2011, the team of scientists tested nasal swabs from more than 900 marine mammals from 10 different species off the Pacific Coast from Alaska to California. They detected H1N1 infection in two northern elephant seals and antibodies to the virus in an additional 28 elephant seals, indicating more widespread exposure.

Neither infected seal appeared to be ill, indicating marine mammals may be infected without showing clinical signs of illness.

The findings are particularly pertinent to people who handle marine mammals, such as veterinarians and animal rescue and rehabilitation workers, Goldstein said. They are also a reminder of the importance of wearing personal protective gear when working around marine mammals, both to prevent workers' exposure to diseases, as well as to prevent the transmission of human diseases to animals.

H1N1 originated in pigs. It emerged in humans in 2009, spreading worldwide as a pandemic. The World Health Organization now considers the H1N1 strain from 2009 to be under control, taking on the behavior of a seasonal virus.

"H1N1 was circulating in humans in 2009," said Goldstein. "The seals on land in early 2010 tested negative before they went to sea, but when they returned from sea in spring 2010, they tested positive. So the question is where did it come from?"

When elephant seals are at sea, they spend most of their time foraging in the northeast Pacific Ocean off the continental shelf, which makes direct contact with humans unlikely, the report said.

The seals had been satellite tagged and tracked, so the researchers knew exactly where they had been and when they arrived on the coast. The first seal traveled from California on Feb. 11 to southeast Alaska to forage off the continental shelf, returning to Point Piedras Blancas near San Simeon, Calif., on April 24. The second seal left Ano Nuevo State Reserve in San Mateo County, Calif., on Feb. 8, traveling to the northeast Pacific and returning on May 5. Infections in both seals were detected within days of their return to land. The report said exposure likely occurred in the seals before they reached land, either while at sea or upon entering the near-shore environment.

The research, led by scientists Goldstein and Walter Boyce at the UC Davis School of Veterinary Medicine's One Health Institute, was conducted with collaborators Nacho Mena and Adolfo García-Sastre at the Icahn School of Medicine at Mount Sinai in New York, who sequenced the virus isolates and characterized their phenotypic properties.

"The study of influenza virus infections in unusual hosts, such as elephant seals, is likely to provide us with clues to understand the ability of influenza virus to jump from one host to another and initiate pandemics," said García-Sastre, professor of microbiology and director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine.

The research was funded primarily through the Centers of Excellence for Influenza Research and Surveillance, a program supported by the National Institute of Allergy and Infectious Disease, and the Tagging of Pacific Predators program, a project of the Census of Marine Life.

Journal Reference:

1. Tracey Goldstein, Ignacio Mena, Simon J. Anthony, Rafael Medina, Patrick W. Robinson, Denise J. Greig, Daniel P. Costa, W. Ian Lipkin, Adolfo Garcia-Sastre, Walter M. Boyce. Pandemic H1N1 Influenza Isolated from Free-Ranging Northern Elephant Seals in 2010 off the Central California Coast. PLoS ONE, 2013; 8 (5): e62259 DOI: 10.1371/journal.pone.0062259

Courtesy: ScienceDaily

Malaria Infected Mosquitoes More Attracted to Human Odor Than Uninfected Mosquitoes

Scientists will attempt to find out how malaria parasites manipulate their mosquito hosts after discovering that smell could be a major factor.

In a study published in PLOS ONEtoday, a team of researchers led by the London School of Hygiene & Tropical Medicine show for the first time that female mosquitoes infected with malaria parasites are significantly more attracted to human odour than uninfected mosquitoes.

This was demonstrated in a laboratory setting in which infected female Anopheles gambiae sensu stricto mosquitoes were attracted to human odours three times more than mosquitoes that were not infected with the malaria-causing Plasmodium falciparum parasite. The rate of landing and biting attempts for infected mosquitoes was around three times greater than uninfected mosquitoes.

The pilot study was conducted in collaboration with Wageningen University and Radboud University Nijmegen Medical Centre in the Netherlands.

Dr James Logan's team has been awarded a three-year grant by the Biotechnology and Biological Sciences Research Council (BBSRC) to investigate how being infected with malaria could cause the mosquitoes to behave differently. If the parasites are manipulating the mosquitoes' sense of smell, increasing the chance they will bite when the parasite is transmissible, then the malaria is more likely to spread.

The scientists, who will work collaboratively with Rothamsted Research, Wageningen University and Radboud University, hope their research will enable the identification of the chemical compounds in human odour to which mosquitoes are attracted and to determine whether infected mosquitoes respond differently to those compounds.

This will provide information that could be used to illuminate how malaria -- a disease which causes more than half a million deaths a year -- is spread from human to human by parasite-infected female mosquitoes which bite people to feed on blood they need in order to reproduce.

Significantly, the results could help identify new compounds which could be used to develop improved mosquito traps that could specifically target malaria-infected mosquitoes before they have the chance to pass on the parasite to the people they bite.

Building on the newly-published pilot study, the team will conduct experiments using a windtunnel which measures the behaviour of mosquitoes towards odours and electrodes which track the response of individual odour-detecting cells from within the antenna of the mosquito in specially-designed secure laboratories at the School to measure the responses of malaria-infected Anopheles gambiae s.s. females to human odours. The scientists also aim to determine whether the response depends on what stage in the lifecycle the parasites are in within insect hosts.

Dr Logan, Senior Lecturer in Medical Entomology and Chief Scientific Officer for arctec, at the London School of Hygiene & Tropical Medicine, said: "It has previously been shown that parasites are able to manipulate the behaviour of insects involved in their transmission and reproductive survival. For example, malaria-infected mosquitoes take larger blood meals than uninfected ones, and will take multiple blood meals.

"We have now shown for the first time that the sense of smell could hold the key to understanding how the parasite successfully manipulates the mosquito to ensure its spread."

"Exploring this further opens up the possibility that we could use this knowledge against the parasite by developing tools with crucial chemicals found in human odour."

Dr Renate Smallegange, a visiting researcher at the School who worked on the pilot study, said: "It is exciting that we are the first ones to prove this phenomenon in a biological relevant system of mosquito, parasite and blood host, and, moreover, in a system affecting millions of people in sub-Saharan Africa."

Journal Reference:

1. Renate C. Smallegange, Geert-Jan van Gemert, Marga van de Vegte-Bolmer, Salvador Gezan, Willem Takken, Robert W. Sauerwein, James G. Logan. Malaria Infected Mosquitoes Express Enhanced Attraction to Human Odor. PLoS ONE, 2013; 8 (5): e63602 DOI:10.1371/journal.pone.0063602

Courtesy: ScienceDaily

Work-Related Stress Linked to Increased Blood Fat Levels, Cardiovascular Health Risks

Spanish researchers have studied how job stress affects cardiovascular health. The results, published in the 'Scandinavian Journal of Public Health', link this situation to dyslipidemia, a disorder that alters the levels of lipids and lipoproteins in the blood.

Experts have been saying for years that emotional stress is linked to the risk of suffering cardiovascular disease as a result of unhealthy habits such as smoking, an unsuitable diet or leading a sedentary lifestyle, among other factors.

Now, a study conducted by the Sociedad de Prevención de Ibermutuamur, in collaboration with experts from the Virgen de la Victoria Hospital (Malaga) and the Santiago de Compostela University, analyses the relationship between job stress and different parameters associated with how fatty acids are metabolised in the body.

The study, published recently in the Scandinavian Journal of Public Health, was conducted on a sample population of more than 90,000 workers undergoing medical check-ups.

"The workers who stated that they had experienced difficulties in dealing with their job during the previous twelve months (8.7% of the sample) had a higher risk of suffering from dyslipidemia," Carlos Catalina, clinical psychologist and an expert in work-related stress, said.

Dyslipidemia is a lipoproteins' metabolic disorder that can manifest itself in an increase in total cholesterol, low-density lipoproteins (LDLs) and triglyceride levels, in addition to a drop in high-density lipoproteins (HDLs).

Changes in the lipid profile

Specifically, in the study the workers with job stress were more likely to suffer from abnormally high levels of LDL cholesterol (the so-called 'bad' cholesterol), excessively low levels of HDL cholesterol (the 'good' cholesterol) and positive atherogenic indices, i.e. potential artery blockage.

"One of the mechanisms that could explain the relationship between stress and cardiovascular risk could be the changes in our lipid profile, which means higher rates of atheromatous plaque accumulation (lipids deposit) in our arteries," Catalina concluded.

Journal Reference:

1. C. Catalina-Romero, E. Calvo, M. A. Sanchez-Chaparro, P. Valdivielso, J. C. Sainz, M. Cabrera, A. Gonzalez-Quintela, J. Roman. The relationship between job stress and dyslipidemia. Scandinavian Journal of Public Health, 2013; 41 (2): 142 DOI: 10.1177/1403494812470400

Courtesy: ScienceDaily

A Cautionary Tale On Genome-Sequencing Diagnostics for Rare Diseases

Children born with rare, inherited conditions known as Congenital Disorders of Glycosylation, or CDG, have mutations in one of the many enzymes the body uses to decorate its proteins and cells with sugars. Properly diagnosing a child with CDG and pinpointing the exact sugar gene that's mutated can be a huge relief for parents -- they better understand what they're dealing with and doctors can sometimes use that information to develop a therapeutic approach. Whole-exome sequencing, an abbreviated form of whole-genome sequencing, is increasingly used as a diagnostic for CDG.

But researchers at Sanford-Burnham Medical Research Institute (Sanford-Burnham) recently discovered three children with CDG who are mosaics -- only some cells in some tissues have the mutation. For that reason, standard exome sequencing initially missed their mutations, highlighting the technique's diagnostic limitations in some rare cases. These findings were published April 4 in the American Journal of Human Genetics.

"This study was one surprise after another," said Hudson Freeze, Ph.D., director of Sanford-Burnham's Genetic Disease Program and senior author of the study. "What we learned is that you have to be careful -- you can't simply trust that you'll get all the answers from gene sequencing alone."

Searching for a rare disease mutation

Complicated arrangements of sugar molecules decorate almost every protein and cell in the body. These sugars are crucial for cellular growth, communication, and many other processes. As a result of a mutation in an enzyme that assembles these sugars, children with CDG experience a wide variety of symptoms, including intellectual disability, digestive problems, seizures, and low blood sugar.

To diagnose CDG, researchers will test the sugar arrangements on a common protein called transferrin. Increasingly, they'll also look for known CDG-related mutations by whole-exome sequencing, a technique that sequences only the small portion of the genome that encodes proteins. The patients are typically three to five years old.

A cautionary tale for genomic diagnostics

In this study, the researchers observed different proportions and representations of sugar arrangements depending on which tissues were examined. In other words, these children have the first demonstrated cases of CDG "mosaicism" -- their mutations only appear in some cell types throughout the body, not all. As a result, the usual diagnostic tests, like whole-exome sequencing, missed the mutations. It was only when Freeze's team took a closer look, examining proteins by hand using biochemical methods, did they identify the CDG mutations in these three children.

The team then went back to the three original children and examined their transferrin again. Surprisingly, these readings, which had previously shown abnormalities, had become normal. Freeze and his team believe this is because mutated cells in the children's livers died and were replaced by normal cells over time.

"If the transferrin test hadn't been performed early on for these children, we never would've picked up these cases of CDG. We got lucky in this case, but it just shows that we can't rely on any one test by itself in isolation," Freeze said.

Journal Reference:

1. Bobby G. Ng, Kati J. Buckingham, Kimiyo Raymond, Martin Kircher, Emily H. Turner, Miao He, Joshua D. Smith, Alexey Eroshkin, Marta Szybowska, Marie E. Losfeld, Jessica X. Chong, Mariya Kozenko, Chumei Li, Marc C. Patterson, Rodney D. Gilbert, Deborah A. Nickerson, Jay Shendure, Michael J. Bamshad, Hudson H. Freeze. Mosaicism of the UDP-Galactose Transporter SLC35A2 Causes a Congenital Disorder of Glycosylation. The American Journal of Human Genetics, 2013; 92 (4): 632 DOI:10.1016/j.ajhg.2013.03.012

Courtesy: ScienceDaily

Unleashing the Watchdog Protein: Research Opens Door to New Drug Therapies for Parkinson's Disease

McGill University researchers have unlocked a new door to developing drugs to slow the progression of Parkinson's disease. Collaborating teams led by Dr. Edward A. Fon at the Montreal Neurological Institute and Hospital -The Neuro, and Dr. Kalle Gehring in the Department of Biochemistry at the Faculty of Medicine, have discovered the three-dimensional structure of the protein Parkin. Mutations in Parkin cause a rare hereditary form of Parkinson's disease and are likely to also be involved in more commonly occurring forms of Parkinson's disease.

The Parkin protein protects neurons from cell death due to an accumulation of defective mitochondria. Mitochondria are the batteries in cells, providing the power for cell functions. This new knowledge of Parkin's structure has allowed the scientists to design mutations in Parkin that make it better at recognizing damaged mitochondria and therefore possibly provide better protection for nerve cells.

The research will be published online May 9 in the journal Science.

"The majority of Parkinson's patients suffer from a sporadic form of the disease that occurs from a complex interplay of genetic and environmental factors which are still not fully understood, explains Dr. Fon, neurologist at The Neuro and head of the McGill Parkinson Program, a National Parkinson Foundation Centre of Excellence. "A minority of patients have genetic mutations in genes such as Parkin that cause the disease. Although there are differences between the genetic and sporadic forms, there is good reason to believe that understanding one will inform us about the other. It's known that toxins that poison mitochondria can lead to Parkinson's-like symptoms in humans and animals. Recently, Parkin was shown to be a key player in the cell's system for identifying and removing damaged mitochondria."

Dr. Gehring, head of McGill's structural biology centre, GRASP, likens Parkin to a watchdog for damaged mitochondria. "Our structural studies show that Parkin is normally kept in check by a part of the protein that acts as a leash to restrict Parkin activity. When we made mutations in this specific 'leash' region in the protein, we found that Parkin recognized damaged mitochondria more quickly. If we can reproduce this response with a drug rather than mutations, we might be able to slow the progression of disease in Parkinson's patients."

Parkin is an enzyme in cells that attaches a small protein, ubiquitin, to other proteins to mark them for degradation. For example, when mitochondria are damaged, Parkin is switched on which leads to the clearing of the dysfunctional mitochondria. This is an important process because damaged mitochondria are a major source of cellular stress and thought to play a central role in the death of neurons in neurodegenerative diseases.

Husband and wife team, Drs. Jean-François Trempe and Véronique Sauvé, are lead authors on the paper. Dr. Sauvé led the Gehring team that used X-ray crystallography to determine the structure of Parkin. Dr. Trempe in the Fon laboratory directed the functional studies of Parkin.

"We are proud to invest in scientific excellence and to fund discovery stage research so that investigators like Dr. Gehring and Fon in Canada can test new theories and pursue promising new leads. We believe that our National Research Program plays an important role in the global search for better treatments and a cure for Parkinson's disease," says Joyce Gordon, President and CEO, Parkinson Society Canada.

Funding was provided by grants from the Parkinson Society Canada, the Canadian Institutes for Health Research, and infrastructure support from the Fonds de recherche Québec and the Canada Foundation for Innovation.

Journal Reference:

1. Jean-François Trempe, Véronique Sauvé, Karl Grenier, Marjan Seirafi, Matthew Y. Tang, Marie Ménade, Sameer Al-Abdul-Wahid, Jonathan Krett, Kathy Wong, Guennadi Kozlov, Bhushan Nagar, Edward A. Fon, Kalle Gehring.Structure of Parkin Reveals Mechanisms for Ubiquitin Ligase Activation. Science, May 9, 2013 DOI:10.1126/science.1237908

Courtesy: ScienceDaily

Potential Flu Pandemic Lurks: Influenza Viruses Circulating in Pigs, Birds Could Pose Risk to Humans

In the summer of 1968, a new strain of influenza appeared in Hong Kong. This strain, known as H3N2, spread around the globe and eventually killed an estimated 1 million people.

A new study from MIT reveals that there are many strains of H3N2 circulating in birds and pigs that are genetically similar to the 1968 strain and have the potential to generate a pandemic if they leap to humans. The researchers, led by Ram Sasisekharan, the Alfred H. Caspary Professor of Biological Engineering at MIT, also found that current flu vaccines might not offer protection against these strains.

"There are indeed examples of H3N2 that we need to be concerned about," says Sasisekharan, who is also a member of MIT's Koch Institute for Integrative Cancer Research. "From a pandemic-preparedness point of view, we should potentially start including some of these H3 strains as part of influenza vaccines."

The study, which appears in the May 10 issue of the journalScientific Reports, also offers the World Health Organization and public-health agencies' insight into viral strains that should raise red flags if detected.

Influenza evolution

In the past 100 years, influenza viruses that emerged from pigs or birds have caused several notable flu pandemics. When one of these avian or swine viruses gains the ability to infect humans, it can often evade the immune system, which is primed to recognize only strains that commonly infect humans.

Strains of H3N2 have been circulating in humans since the 1968 pandemic, but they have evolved to a less dangerous form that produces a nasty seasonal flu. However, H3N2 strains are also circulating in pigs and birds.

Sasisekharan and his colleagues wanted to determine the risk of H3N2 strains re-emerging in humans, whose immune systems would no longer recognize the more dangerous forms of H3N2. This type of event has a recent precedent: In 2009, a strain of H1N1 emerged that was very similar to the virus that caused a 1918 pandemic that killed 50 million to 100 million people.

"We asked if that could happen with H3," Sasisekharan says. "You would think it's more readily possible with H3 because we observe that there seems to be a lot more mixing of H3 between humans and swine."

Genetic similarities

In the new study, the researchers compared the 1968 H3N2 strain and about 1,100 H3 strains now circulating in pigs and birds, focusing on the gene that codes for the viral hemagglutinin (HA) protein.

After comparing HA genetic sequences in five key locations that control the viruses' interactions with infected hosts, the researchers calculated an "antigenic index" for each strain. This value indicates the percentage of these genetic regions identical to those of the 1968 pandemic strain and helps determine how well an influenza virus can evade a host's immune response.

The researchers also took into account the patterns of attachment of the HA protein to sugar molecules called glycans. The virus' ability to attach to glycan receptors found on human respiratory-tract cells is key to infecting humans.

Seeking viruses with an antigenic index of at least 49 percent and glycan-attachment patterns identical to those of the 1968 virus, the research team identified 581 H3 viruses isolated since 2000 that could potentially cause a pandemic. Of these, 549 came from birds and 32 from pigs.

The researchers then exposed some of these strains to antibodies provoked by the current H3 seasonal-flu vaccines. As they predicted, these antibodies were unable to recognize or attack these H3 strains. Of the 581 HA sequences, six swine strains already contain the standard HA mutations necessary for human adaptation, and are thus capable of entering the human population either directly or via genetic reassortment, Sasisekharan says.

"One of the amazing things about the influenza virus is its ability to grab genes from different pools," he says. "There could be viral genes that mix among pigs, or between birds and pigs."

Sasisekharan and colleagues are now doing a similar genetic study of H5 influenza strains. The H3 study was funded by the National Institutes of Health and the National Science Foundation.

Journal Reference:

1. Kannan Tharakaraman, Rahul Raman, Nathan W. Stebbins, Karthik Viswanathan, Viswanathan Sasisekharan, Ram Sasisekharan. Antigenically intact hemagglutinin in circulating avian and swine influenza viruses and potential for H3N2 pandemic. Scientific Reports, 2013; 3 DOI: 10.1038/srep01822

Courtesy: ScienceDaily

Risks of H7N9 Infection Mapped

A map of avian influenza (H7N9) risk is presented in Biomed Central's open access journal Infectious Diseases of Poverty today. The map is composed of bird migration patterns, and adding in estimations of poultry production and consumption, which are used to infer future risk and to advise on ways to prevent infection.

As of today, there have been 127 confirmed cases of H7N9 in mainland China with 27 deaths. A lack of information about the virus and its mode of transmission has led to public concerns that H7N9 could be a pandemic waiting to happen.

To quantify the risk of this happening scientists from the Hong Kong Baptist University and Chinese University of Hong Kong have generated a map of H7N9 risk in eastern China. The map is based on the northwards migratory patterns of birds (from the 4th February to the end of April) using environmental and meteorological data over the same 12 weeks -- from Zhejiang, Shanghai, and Jiangsu, to Liaoning, Jilin, and Heilongjiang.

The distribution of potentially infected poultry was also included in the model. The majority of early cases of H7N9 were found in Shanghai, but Shanghai is not a big poultry exporter so the model shows limited transmission via this route. In contrast, Jiangsu distributes poultry to Shanghai, Zhejiang, and beyond.

Prof Jiming Liu who led the study explained, "By basing our model on wild bird migration and distribution of potentially infected poultry we are able to produce a time line of the estimated risk of human infection with H7N9. The preliminary results of our study made a prediction of bird flu risk which could explain the pattern of the most recent cases. By extending the model we will be able to predict future infection risks across central and western China, which will aid in surveillance and control of H7N9 infections. Since the effect of poultry-to-poultry infection is not really understood it may become necessary to regulate the activity of poultry markets."

Prof Xiao-Nong Zhou from the Chinese Center for Disease Control and Prevention who was also involved in this study commented, "We are continuing to work on research into the sources of infection of H7N9 and the mode of transmission. However so far there is no evidence of the sustained human-to-human transmission required for a pandemic to occur."

Journal Reference:

1. Benyun Shi, Shang Xia, Guo-Jing Yang, Xiao-Nong Zhou, Jiming Liu. Inferring the potential risks of H7N9 infection by spatiotemporally characterizing bird migration and poultry distribution in eastern China. Infectious Diseases of Poverty, 2013; 2 (1): 8 DOI: 10.1186/2049-9957-2-8

Courtesy: ScienceDaily

Discovery Helps Show How Breast Cancer Spreads

Researchers at Washington University School of Medicine in St. Louis have discovered why breast cancer patients with dense breasts are more likely than others to develop aggressive tumors that spread. The finding opens the door to drug treatments that prevent metastasis.

Researchers at Washington University School of Medicine in St. Louis have discovered why breast cancer patients with dense breasts are more likely than others to develop aggressive tumors that spread. The finding opens the door to drug treatments that prevent metastasis. It has long been known that women with denser breasts are at higher risk for breast cancer. This greater density is caused by an excess of a structural protein called collagen. Collagen fiber alignment at the tumor boundary (dashed lines) is predictive of prognosis. Fibers that tend to be perpendicular to the tumor surface (top right, for example) encourage metastasis and indicate a poor prognosis. Fibers that run parallel to the tumor surface (bottom right) protect against cancer spreading. Tumors without DDR2 or SNAIL1 tend to show the protective parallel fiber alignment. (Credit: Nature Cell Biology)

It has long been known that women with denser breasts are at higher risk for breast cancer. This greater density is caused by an excess of a structural protein called collagen.

"We have shown how increased collagen in the breasts could increase the chances of breast tumors spreading and becoming more invasive," says Gregory D. Longmore, MD, professor of medicine. "It doesn't explain why women with dense breasts get cancer in the first place. But once they do, the pathway that we describe is relevant in causing their cancers to be more aggressive and more likely to spread."

The results appear online May 5 inNature Cell Biology.

Working in mouse models of breast cancer and breast tumor samples from patients, Longmore and his colleagues showed that a protein that sits on the surface of tumor cells, called DDR2, binds to collagen and activates a multistep pathway that encourages tumor cells to spread.

"We had no idea DDR2 would do this," says Longmore, also professor of cell biology and physiology. "The functions of DDR2 are not well understood, and it has not been implicated in cancer -- and certainly not in breast cancer -- until now.

At the opposite end of the chain of events initiated by DDR2 is a protein called SNAIL1, which has long been associated with breast cancer metastasis. Longmore and his colleagues found that DDR2 is one factor helping to maintain high levels of SNAIL1 inside a tumor cell's nucleus, a necessary state for a tumor cell to spread. Though they found it is not the only protein keeping SNAIL1 levels high, Longmore says DDR2 is perhaps the one with the most potential to be inhibited with drugs.

"It's expressed only at the edge of the tumor," says Longmore, a physician at Siteman Cancer Center at Washington University and Barnes-Jewish Hospital and co-director of the Section of Molecular Oncology. "And it's on the surface of the cells, which makes it very nice for developing drugs because it's so much easier to target the outside of cells."

Longmore emphasizes that DDR2 does not initiate the high levels of SNAIL1. But it is required to keep them elevated. This mechanism that keeps tumor cells in a state that encourages metastasis requires constant signaling -- meaning constant binding of DDR2 to collagen.

If that continuous signal is blocked, the cell remains cancerous, but it is no longer invasive. So a drug that blocks DDR2 from binding with collagen won't destroy the tumor, but it could inhibit the invasion of these tumors into surrounding tissue and reduce metastasis.

One possible way DDR2 may govern metastasis is its influence on the alignment of collagen fibers. If fibers are aligned parallel to the tumor's surface, the tumor is less likely to spread. While fibers aligned perpendicular to the surface of the tumor provide a path for the tumor cells to follow and encourage spreading. Tumors without DDR2 or SNAIL1 tend to show the parallel fiber alignment that is protective against spreading.

"This whole notion of fiber alignment and the tumor interface is a hot topic right now," Longmore says. "Our co-authors at the University of Wisconsin have developed a scoring method for collagen alignment that correlates with prognosis. And the bad prognosis disappears when you take away DDR2."

With the current emphasis on genetic mutations in cancer, Longmore is careful to point out that 70 percent of invasive ductal breast cancers show DDR2. But in 95 percent of these tumors the genes in this pathway -- from DDR2 to SNAIL1 -- are entirely normal, without mutations.

"If you did genomic sequencing, all of these particular genes would be normal," Longmore says. "You have to be careful not to just focus on mutations in cancer. This is an example of normal genes put together in an aberrant situation. The change in the environment -- the tumor and its surroundings -- causes the abnormal expression of these proteins. It is abnormal, but it's not caused by a gene mutation."

In early drug development efforts, Longmore and his colleagues have done some preliminary work looking for small molecules that may inhibit DDR2 binding to collagen.

"Currently there are no DDR2 specific inhibitors," Longmore says. "But there is great interest and work being done here and elsewhere to develop them."

Journal Reference:

1. Kun Zhang, Callie A. Corsa, Suzanne M. Ponik, Julie L. Prior, David Piwnica-Worms, Kevin W. Eliceiri, Patricia J. Keely, Gregory D. Longmore. The collagen receptor discoidin domain receptor 2 stabilizes SNAIL1 to facilitate breast cancer metastasis. Nature Cell Biology, 2013; DOI: 10.1038/ncb2743

Courtesy: ScienceDaily

Individual Brain Cells Track Where We Are and How We Move

Leaving the house in the morning may seem simple, but with every move we make, our brains are working feverishly to create maps of the outside world that allow us to navigate and to remember where we are.

Place cells in the real world (l) and in virtual reality. Place cells in the real world (left): The picture on the left shows the top-down view of a room in which a rat runs. There are four colorful walls and a check pattern on the floor. In the middle of the room, there is a narrow track (white line) on which the rat runs. Spikes fired by a neuron are shown by blue tick marks above and below the white track. Spikes fired when the rat runs from left-to-right are shown below the track and those spikes fired when the rat runs from right-to-left are shown above the track. These data were recorded in the real world. Notice that the spikes (blue tick marks) occur at the same absolute position hence these are called place cells. Place cells in virtual reality (right): These data were recorded in the virtual world. Note that the virtual world looks similar to the real world (other image). When the rat runs in this virtual world, the neurons fire at the same relative distance on the track in both movement directions, not at the same position as it does in the real world. Scientists hypothesize that the neurons are actually computing relative distances using cues on the walls and self-movement in the virtual world. In the real word, the presence of nonspecific sensory stimuli on the track, such as smells and textures, are hypothesized to make the neurons active at the same position. (Credit: Image courtesy of University of California - Los Angeles)

Take one step out the front door, and an individual brain cell fires. Pass by your rose bush on the way to the car, another specific neuron fires. And so it goes. Ultimately, the brain constructs its own pinpoint geographical chart that is far more precise than anything you'd find on Google Maps.

But just how neurons make these maps of space has fascinated scientists for decades. It is known that several types of stimuli influence the creation of neuronal maps, including visual cues in the physical environment -- that rose bush, for instance -- the body's innate knowledge of how fast it is moving, and other inputs, like smell. Yet the mechanisms by which groups of neurons combine these various stimuli to make precise maps are unknown.

To solve this puzzle, UCLA neurophysicists built a virtual-reality environment that allowed them to manipulate these cues while measuring the activity of map-making neurons in rats. Surprisingly, they found that when certain cues were removed, the neurons that typically fire each time a rat passes a fixed point or landmark in the real world instead began to compute the rat'srelative position, firing, for example, each time the rodent walked five paces forward, then five paces back, regardless of landmarks. And many other mapping cells shut down altogether, suggesting that different sensory cues strongly influence these neurons.

Finally, the researchers found that in this virtual world, the rhythmic firing of neurons that normally speeds up or slows down depending on the rate at which an animal moves, was profoundly altered. The rats' brains maintained a single, steady rhythmic pattern.

The findings, reported in the May 2 online edition of the journal Science,provide further clues to how the brain learns and makes memories.

The mystery of how cells determine place

"Place cells" are individual neurons located in the brain's hippocampus that create maps by registering specific places in the outside environment. These cells are crucial for learning and memory. They are also known to play a role in such conditions as post-traumatic stress disorder and Alzheimer's disease when damaged.

For some 40 years, the thinking had been that the maps made by place cells were based primarily on visual landmarks in the environment, known as distal cues -- a tall tree, a building -- as well on motion, or gait, cues. But, as UCLA neurophysicist and senior study author Mayank Mehta points out, other cues are present in the real world: the smell of the local pizzeria, the sound of a nearby subway tunnel, the tactile feel of one's feet on a surface. These other cues, which Mehta likes to refer to as "stuff," were believed to have only a small influence on place cells.

Could it be that these different sensory modalities led place cells to create individual maps, wondered Mehta, a professor with joint appointments in the departments of neurology, physics and astronomy. And if so, do these individual maps cooperate with each other, or do they compete? No one really knew for sure.

Virtual reality reveals new clues

To investigate, Mehta and his colleagues needed to separate the distal and gait cues from all the other "stuff." They did this by crafting a virtual-reality maze for rats in which odors, sounds and all stimuli, except distal and gait cues, were removed. As video of a physical environment was projected around them, the rats, held by a harness, were placed on a ball that rotated as they moved. When they ran, the video would move along with them, giving the animals the illusion that they were navigating their way through an actual physical environment.

As a comparison, the researchers had the rats -- six altogether -- run a real-world maze that was visually identical to the virtual-reality version but that included the additional "stuff" cues. Using micro-electrodes 10 times thinner than a human hair, the team measured the activity of some 3,000 space-mapping neurons in the rats' brains as they completed both mazes.

What they found intrigued them. The elimination of the "stuff" cues in the virtual-reality maze had a huge effect: Fully half of the neurons being recorded became inactive, despite the fact that the distal and gate cues were similar in the virtual and real worlds. The results, Mehta said, show that these other sensory cues, once thought to play only a minor role in activating the brain, actually have a major influence on place cells.

And while in the real world, place cells responded to fixed, absolute positions, spiking at those same positions each time rats passed them, regardless of the direction they were moving -- a finding consistent with previous experiments -- this was not the case in the virtual-reality maze.

"In the virtual world," Mehta said, "we found that the neurons almost never did that. Instead, the neurons spiked at the same relative distance in the two directions as the rat moved back and forth. In other words, going back to the front door-to-car analogy, in a virtual world, the cell that fires five steps away from the door when leaving your home would not fire five steps away from the door upon your return. Instead, it would fire five steps away from the car when leaving the car. Thus, these cells are keeping track of the relative distance traveled rather than absolute position. This gives us evidence for the individual place cell's ability to represent relative distances."

Mehta thinks this is because neuronal maps are generated by three different categories of stimuli -- distal cues, gait and "stuff" -- and that all are competing for control of neural activity. This competition is what ultimately generates the "full" map of space.

"All the external stuff is fixed at the same absolute position and hence generates a representation of absolute space," he said. "But when all the stuff is removed, the profound contribution of gait is revealed, which enables neurons to compute relative distances traveled."

The researchers also made a new discovery about the brain's theta rhythm. It is known that place cells use the rhythmic firing of neurons to keep track of "brain time," the brain's internal clock. Normally, Mehta said, the theta rhythm becomes faster as subjects run faster, and slower as running speed decreases. This speed-dependent change in brain rhythm was thought to be crucial for generating the 'brain time' for place cells. But the team found that in the virtual world, the theta rhythm was uninfluenced by running speed.

"That was a surprising and fascinating discovery, because the 'brain time' of place cells was as precise in the virtual world as in the real world, even though the speed-dependence of the theta rhythm was abolished," Mehta said. "This gives us a new insight about how the brain keeps track of space-time."

The researchers found that the firing of place cells was very precise, down to one-hundredth of a second, "so fast that we humans cannot perceive it but neurons can," Mehta said. "We have found that this very precise spiking of neurons with respect to 'brain-time' is crucial for learning and making new memories."

Mehta said the results, taken together, provide insight into how distinct sensory cues both cooperate and compete to influence the intricate network of neuronal activity. Understanding how these cells function is key to understanding how the brain makes and retains memories, which are vulnerable to such disorders as Alzheimer's and PTSD.

"Ultimately, understanding how these intricate neuronal networks function is a key to developing therapies to prevent such disorders," he said.

Other authors of the study included Pascal Ravassard, Ashley Kees and Bernard Willers, all lead authors, and David Ho, Daniel A. Aharoni, Jesse Cushman and Zahra M. Aghajan of UCLA. Funding was provided by the W.M. Keck foundation, a National Science Foundation career award grant and a National Institutes of Health grant (5R01MH092925-02).

Journal Reference:

1. P. Ravassard, A. Kees, B. Willers, D. Ho, D. A. Aharoni, J. Cushman, Z. M. Aghajan, M. R. Mehta. Multisensory Control of Hippocampal Spatiotemporal Selectivity.Science, 2013; DOI: 10.1126/science.1232655

Courtesy: ScienceDaily

Attention Baby Boomers: Get Screened for Hepatitis C

If you were born during 1945-1965, talk to your doctor about getting tested for hepatitis C. Baby boomers are five times more likely than other adults to be infected. In fact, 75 percent of adults with hepatitis C were born during these years.

The word "hepatitis" means swelling of the liver. Hepatitis is most often caused by a virus. In the United States, the most common type of viral hepatitis is hepatitis C. Hepatitis C is primarily spread through contact with blood from an infected person. More than 15,000 Americans, most of them baby boomers, die each year from hepatitis C-related illness.

Deaths related to hepatitis C have been on the rise and are expected to increase. Hepatitis C is a leading cause of liver cancer and the leading reason for liver transplants. Other serious health problems related to hepatitis C include:

• Liver damage
• Cirrhosis
• Liver failure

The reason that baby boomers have the highest rates of hepatitis C is not completely understood. Most boomers may have become infected in the 1970s and 1980s when rates of hepatitis C were the highest. Many baby boomers could have gotten infected from tainted blood and blood products before testing of the blood supply began in 1992. Others may have become infected from injecting drugs, even if only once in the past. Still, many baby boomers do not know how or when they were infected.

People with hepatitis C often have no symptoms and can live for decades without feeling sick. As baby boomers grow older, there is a greater chance that they will develop life-threatening liver disease from hepatitis C.

Risk factors for hepatitis infection include:

• History of blood transfusions or other blood products (before July 1992)
• Organ transplant before widespread testing for HIV and hepatitis (before July 1992)
• Long-term dialysis treatment
• Exposure to hepatitis C such as through a healthcare setting (healthcare needle sticks)
• Infection with HIV, the AIDS virus
• Children born to mothers who have hepatitis C
• Any past use of injected illegal drugs
• Having received a tattoo with needles that were not properly disinfected

The only way to know if you have hepatitis C is to get tested. Early detection can save lives. There is a simple blood test to determine if a person has ever been infected with the hepatitis C virus. It is estimated that one-time testing of everyone born during 1945 through 1965 will prevent more than 120,000 deaths.

Knowing your diagnosis early and getting treatment can help prevent liver damage, cirrhosis, and even liver cancer. There are no vaccines to prevent hepatitis C.

Many people who have been diagnosed with hepatitis C can be successfully treated with medications called antivirals. Two new medicines are now available (telaprevir and boceprevir), that when added to the standard treatment can increase the effectiveness and shorten treatment time for many people. For many people, medical treatment can result in clearing hepatitis C from the bloodstream.

Talk to your doctor about getting tested -- it could save your life!

Story Source:

The above story is reprinted from materials provided byAssociation for Professionals in Infection Control and Epidemiology (APIC).

Courtesy: ScienceDaily