Swinburne researchers have developed a technique to create a highly sensitive surface for measuring the concentration of a peptide that is a biomarker for early stage Alzheimer’s disease.
(Image caption: Ultrashort-laser pulses were used to write ripples on the surface of sapphire. The self-organised nano-structure of ripples (seen in the image) is a perfect sensing surface after coating with a nanometre-thin layer of gold made by evaporation or sputtering. Such surface ripples were used in the study of amyloid detection.)
Alzheimer’s disease was first recorded more than 100 years ago, but there is still no effective therapy to stop or slow the progression of the disease. Sufferers can lose up to 60 per cent of their neuronal cells before a diagnosis is obtained.
Diagnosis at the very early stages before neuronal degeneration has begun is vital for testing and developing new treatments.
Abnormality of the beta amyloid peptide in cerebrospinal fluid appears to be the earliest and most significant marker of Alzheimer’s. Currently there are no standardised tests to detect these biomarkers.
The researchers have developed a sensor based on nanotechnology that outperforms commercial sensors and demonstrates fast and reliable measurement of beta amyloid oligomers at low concentrations.
The key to the high sensitivity is the laser nano-textured gold coated surface. This sensor can identify concentrations of beta amyloid in a quantitative manner for the first time.
“We showed that sensors based on light scattering can indeed deliver QUANTATIVE measurements and they can be made fast,” Professor of Nanophotonics Saulius Juodkazis said.
“The sensor platform we developed by laser nano-texturing of surfaces is delivering results of the highest sensitivity and repeatability.
“The challenge is to create fast and efficient fabrication of sensors based on nanotechnology and develop new analytical methods of detection. This means we should be able to detect markers of diseases at far lower levels.”
Surface enhanced Raman spectroscopy (SERS) is one of the most sensitive and highly specific label-free detection methods which may evolve as a detection technique for different forms of beta amyloid or as a rapid, low cost technique to validate new biomarkers before developing standard assays for enzyme-linked immunosorbent assays (ELISAs).
This research is a PhD project work of Dr Ricardas Buividas who received his doctorate in May 2014. It was published in the Journal of Biophotonics.
While reading, children and adults alike must avoid confusing mirror-image letters (like b/d or p/q). Why is it difficult to differentiate these letters? When learning to read, our brain must be able to inhibit the mirror-generalization process, a mechanism that facilitates the recognition of identical objects regardless of their orientation, but also prevents the brain from differentiating letters that are different but symmetrical. A study conducted by the researchers of the Laboratoire de Psychologie du Développement et de l’Education de l’Enfant (CNRS / Université Paris Descartes / Université de Caen Basse-Normandie) is available on the website of the Psychonomic Bulletin & Review (Online First Articles).
In recent years, many studies on the process of learning to read have been based on the neuronal recycling hypothesis: the reuse of old brain mechanisms in a new adaptive role —a kind of “biological trick.” Specifically, neurons that are originally dedicated to the rapid identification of objects in the environment, through the mirror-generalization process, are “repurposed” during childhood to specialize in the visual recognition of letters and words.
In this study, the researchers showed 80 young adults pairs of images, first two letters and then two animals, asking them to determine whether they were identical. The readers consistently spent more time determining that two animal images, when preceded by mirror-image letters, were indeed identical. This increase in response time is called “negative priming”: the readers had to inhibit the mirror-generalization process in order to distinguish letters like b/d or p/q. They then needed a little more time to reactivate this strategy when it became useful again to quickly identify animals.
These results show that even adults need to inhibit the mirror-generalization process to avoid reading errors. Children must therefore learn to inhibit this strategy when learning to read. A failure of cognitive inhibition during the recycling of visual neurons in the brain could thus be a factor in dyslexia— a direction worth exploring, in light of these findings.
Biologists ID process producing neuronal diversity in fruit flies' visual system
New York University biologists have identified a mechanism that helps explain how the diversity of neurons that make up the visual system is generated.
“Our research uncovers a process that dictates both timing and cell survival in order to engender the heterogeneity of neurons used for vision,” explains NYU Biology Professor Claude Desplan, the study’s senior author.
The study’s other co-authors were: Claire Bertet, Xin Li, Ted Erclik, Matthieu Cavey, and Brent Wells—all postdoctoral fellows at NYU.
Their work, which appears in the latest issue of the journal Cell, centers on neurogenesis—the process by which neurons are created.
A central challenge in developmental neurobiology is to understand how progenitors—stem cells that differentiate to form one or more kinds of cells—produce the vast diversity of neurons, glia, and non-neuronal cells found in the adult Central Nervous System (CNS). Temporal patterning is one of the core mechanisms generating this diversity in both invertebrates and vertebrates. This process relies on the sequential expression of transcription factors into progenitors, each specifying the production of a distinct neural cell type.
In the Cell paper, the researchers studied the formation of the visual system of the fruit fly Drosophila. Their findings revealed that this process, which relies on temporal patterning of neural progenitors, is more complex than previously thought.
They demonstrate that in addition to specifying the production of distinct neural cell type over time, temporal factors also determine the survival or death of these cells as well as the mode of division of progenitors. Thus, temporal patterning of neural progenitors generates cell diversity in the adult visual system by specifying the identity, the survival, and the number of each unique neural cell type.
How nerve cells within the brain communicate with each other over long distances has puzzled scientists for decades. The way networks of neurons connect and how individual cells react to incoming pulses in principle makes communication over large distances impossible. Scientists from Germany and France provide now a possible answer how the brain can function nonetheless: by exploiting the powers of resonance.
(Image caption: Resonance in the activity of nerve cells (left) allows activity within the brain to travel over large distances, e.g. from the back of the head to the front during the processing of visual stimuli. Credit: Gunnar Grah/BrainLinks-BrainTools)
As Gerald Hahn, Alejandro F. Bujan and colleagues describe in the journal “PLoS Computational Biology”, the ability of networks of neurons to resonate can amplify oscillations in the activity of nerve cells, allowing signals to travel much farther than in the absence of resonance. The team from the cluster of excellence BrainLinks-BrainTools and the Bernstein Center at the University of Freiburg and the UNIC department of the French Centre national de la recherche scientifique in Gif-sur-Yvette created a computer model of networks of nerve cells and analyzed its properties for signal propagation.
Earlier propositions how information travels through the brain had the flaw of being biologically implausible. They either postulated strong connections between distant brain areas for which there was no evidence, or they required a global mechanism setting these distant parts of the brain into linked oscillations. However, nobody could explain how this could actually be implemented.
The simulation study of Hahn and Bujan required neither unrealistic network properties nor the existence of a pacemaker for the brain. Instead, they found that resonance could be the key to long-distance communication in networks with relatively few and weak connections, as it is the case in the brain. Not all nerve cells excite other cells; some inhibit the activity of others. This means that the activity in a network can oscillate around a certain level of activity as a result of the interplay of excitation and inhibition. These networks typically have preferred frequencies at which oscillations are particularly strong, just as a taut string on a violin has a preferred frequency. If the activity tunes into this frequency, pulses propagate much farther. As the scientists point out, the combination of oscillatory signals together with resonance induced amplification may be the only possible form of long distance communication in certain cases. They further suggest that a network’s ability to change its preferred frequency may play a role in the way how information is at times processed differently in the brain.
How Alzheimer’s Peptides Shut Down Cellular Powerhouses
The failing in the work of nerve cells: An international team of researchers led by Prof. Dr. Chris Meisinger from the Institute of Biochemistry and Molecular Biology of the University of Freiburg has discovered how Alzheimer’s disease damages mitochondria, the powerhouses of the cell. For several years researchers have known that the cellular energy supply of brain cells is impaired in Alzheimer’s patients. They suspect this to be the cause of premature death of nerve cells that occurs in the course of the disease. Little is known about the precise cause of this neuronal cell death, and many approaches and attempts to find an effective therapy have failed to make an impact. What is certain is that a tiny protein fragment by the name of “amyloid-beta” plays a key role in the process. Meisinger, a member of the Cluster of Excellence BIOSS Centre for Biological Signalling Studies of the University of Freiburg, and his team have now demonstrated how this protein fragment blocks the maturation of protein machines that are responsible for the production of energy inside the cellular powerhouses. The researchers demonstrated this with the help of model organisms and with brain samples from Alzheimer’s patients. “The elucidation of this key component of the disease mechanism will enable us to develop new therapies and improve diagnostics in the future,” explains Meisinger. The findings were published in the journal Cell Metabolism.
Mitochondria are made up of around 1500 different proteins. Most of them need to migrate to the cellular powerhouses before taking up their work. This import is facilitated by a so-called signaling sequence – tiny protein extensions that transport the protein into the mitochondria. Once the protein is inside, the signaling sequence is normally removed. Dirk Mossmann and Dr. Nora Vögtle from Meisinger’s research team have now discovered that the amyloid-beta peptide prevents mitochondria from removing these signaling sequences. As a consequence, incomplete proteins accumulate in the mitochondria. Since the signaling sequences remain attached, the proteins are unstable and can no longer adequately carry out their function in energy metabolism. The researchers demonstrated that modified yeast cells producing the amyloid-beta protein generate less energy and accumulate more harmful substances.
In the brain, the mechanism probably leads to the death of nerve cells: The brain shrinks and the patient suffers from dementia. The researchers are currently developing an Alzheimer’s blood test to detect the accumulation of mitochondrial precursor proteins. They suspect that the mitochondrial alterations observed in nerve cells will also be detected in the blood cells of Alzheimer’s patients.
Different forms of Alzheimer’s have similar effects on brain networks
Brain networks break down similarly in rare, inherited forms of Alzheimer’s disease and much more common uninherited versions of the disorder, a new study has revealed.
Scientists at Washington University School of Medicine in St. Louis have shown that in both types of Alzheimer’s, a basic component of brain function starts to decline about five years before symptoms, such as memory loss, become obvious.
The breakdown occurs in resting state functional connectivity, which involves groups of brain regions with activity levels that rise and fall in coordination with each other. Scientists believe this synchronization helps the regions form networks that work together or stay out of each other’s way during mental tasks.
“The brain networks affected by inherited Alzheimer’s disease in a 30-year-old are very similar to the networks affected by uninherited Alzheimer’s disease in a 60-, 70- or 80-year-old,” said senior author Beau Ances, MD, PhD. “This affirms that what we learn by studying inherited Alzheimer’s, which appears at younger ages, will help us better understand and treat more common forms of the disease.”
According to Ances, the results show that functional connectivity may help scientists monitor the effects of treatment as patients progress through the transition between early disease and the first appearance of obvious symptoms.
“Right now, this period when functional connectivity begins breaking down is a time when family and loved ones may start noticing little changes in personality or mental function in someone with the disease, but not significant enough changes to cause real alarm,” Ances said. “The hope is that one day treatment already will be well underway before these sorts of changes begin — we want to slow or stop the damage caused by Alzheimer’s years earlier.”
Inherited Alzheimer’s disease can strike very early in life, causing symptoms in patients as young as their 30s or 40s. Identifying the mutations that cause these forms of the disease has helped scientists find proteins that become problematic in more common forms of Alzheimer’s, which typically appear decades later.
Researchers have long assumed that additional connections exist between inherited and uninherited Alzheimer’s disease, but until recently they have not had sufficient data to directly test many of those connections. Challenges have included the small number of people with inherited Alzheimer’s, and the slow development of both forms of the disease.
Scientists at the Charles F. and Joanne Knight Alzheimer’s Disease Research Center at Washington University began to tackle the first challenge five years ago by organizing the Dominantly Inherited Alzheimer’s Network (DIAN), an international network for identifying and studying families with inherited forms of the disease. The network now includes nearly 400 families.
To address the second challenge, Washington University researchers at the center have been gathering extensive health data on seniors through long-term projects such as the Healthy Aging and Senile Dementia Study, which is entering its 31st year.
These pools of data allowed Ances, an associate professor of neurology, to compare the effects of inherited and uninherited Alzheimer’s on functional connectivity. Scientists assess functional connectivity by scanning the brains of research participants while they daydream.
“The question was, where does the decline of functional connectivity fit in the whole picture of the development of Alzheimer’s disease?” Ances said. “And it clearly does have a place in the middle stages of the disease.”
That’s not the best place to look for an initial diagnosis, according to Ances. Ideally, scientists want to start treating Alzheimer’s disease as soon as possible.
“What this does tell us, though, is that functional connectivity may help us track the progression of Alzheimer’s in patients who are first diagnosed when they’re beginning to show early signs of dementia,” he said.
Dyslexic Readers Have Disrupted Network Connections in the Brain
Dyslexia, the most commonly diagnosed learning disability in the United States, is a neurological reading disability that occurs when the regions of the brain that process written language don’t function normally.
The use of non-invasive functional neuroimaging tools has helped characterize how brain activity is disrupted in dyslexia. However, most prior work has focused on only a small number of brain regions, leaving a gap in our understanding of how multiple brain regions communicate with one another through networks, called functional connectivity, in persons with dyslexia.
This led neuroscience PhD student Emily Finn and her colleagues at the Yale University School of Medicine to conduct a whole-brain functional connectivity analysis of dyslexia using functional magnetic resonance imaging (fMRI). They report their findings in the current issue of Biological Psychiatry.
"In this study, we compared fMRI scans from a large number of both children and young adults with dyslexia to scans of typical readers in the same age groups. Rather than activity in isolated brain regions, we looked at functional connectivity, or coordinated fluctuations between pairs of brain regions over time," explained Finn.
In total, they recruited and scanned 75 children and 104 adults. Finn and her colleagues then compared the whole-brain connectivity profiles of the dyslexic readers to the non-impaired readers, which revealed widespread differences.
Dyslexic readers showed decreased connectivity within the visual pathway as well as between visual and prefrontal regions, increased right-hemisphere connectivity, reduced connectivity in the visual word-form area, and persistent connectivity to anterior language regions around the inferior frontal gyrus. This altered connectivity profile is consistent with dyslexia-related reading difficulties.
Dr. John Krystal, Editor of Biological Psychiatry, said, “This study elegantly illustrates the value of functional imaging to map circuits underlying problems with cognition and perception, in this case, dyslexia.”
"As far as we know, this is one of the first studies of dyslexia to examine differences in functional connectivity across the whole brain, shedding light on the brain networks that crucially support the complex task of reading," added Finn. "Compared to typical readers, dyslexic readers had weaker connections between areas that process visual information and areas that control attention, suggesting that individuals with dyslexia are less able to focus on printed words."
Additionally, young-adult dyslexic readers maintained high connectivity to brain regions involved in phonology, suggesting that they continue to rely on effortful “sounding out” strategies into adulthood rather than transitioning to more automatic, visual-based strategies for word recognition.
A better understanding of brain organization in dyslexia could potentially lead to better interventions to help struggling readers.
Fragmented REM sleep may hinder effective treatment of mental health condition
The effectiveness of post-traumatic stress disorder (PTSD) treatment may hinge significantly upon sleep quality, report researchers at the University of California, San Diego School of Medicine and Veterans Affairs San Diego Healthcare System in a paper published today in the Journal of Neuroscience.
“I think these findings help us understand why sleep disturbances and nightmares are such important symptoms in PTSD,” said Sean P.A. Drummond, PhD, professor of psychiatry and director of the Behavioral Sleep Medicine Program at the VA San Diego Healthcare System. “Our study suggests the physiological mechanism whereby sleep difficulties can help maintain PTSD. It also strongly implies a mechanism by which poor sleep may impair the ability of an individual to fully benefit from exposure-based PTSD treatments, which are the gold standard of interventions.
“The implication is that we should try treating sleep before treating the daytime symptoms of PTSD and see if those who are sleeping better when they start exposure therapy derive more benefit.”
PTSD is an often difficult-to-treat mental health condition triggered by a terrifying event. It is frequently associated with persons who have served in war zones and is characterized by severe anxiety, flashbacks, nightmares and uncontrollable thoughts, often fearful. Research has shown that fear conditioning, considered an animal model of PTSD, results in disruption of animals’ rapid eye movement (REM) sleep – periods of deeper, dream-filled slumber. Fear conditioning is a form of learning in which the animal model is trained to associate an aversive stimulus, such as an electrical shock, with a neutral stimulus, such as a tone or beep.
Drummond and colleagues investigated the impact of fear conditioning – and another form of behavioral training called safety signal learning – upon human REM sleep, using 42 healthy volunteers tested over three consecutive days and nights. Safety signals are learned cues that predict the non-occurrence of an aversive event.
“We examined the relationship between REM sleep and the ability to learn – and consolidate memory for – stimuli that represent threats and that represent safety,” said Drummond.
“In PTSD, humans learn to associate threat with a stimulus that used to be neutral or even pleasant. Often, this fear generalizes so that they have a hard time learning that other stimuli are safe. For example, a U.S. Marine in Iraq might suffer trauma when her personnel carrier is blown up by road side bomb hidden in trash alongside the road. When she comes home, she should learn that trash on the side of I-5 does not pose a threat – it’s a safe stimulus – but that may be difficult for her.”
The researchers found that increased safety signaling was associated with increased REM sleep consolidation at night and that the quality of overnight REM sleep was related to how well volunteers managed fear conditioning.
Drummond said stimuli representing safety increased human REM sleep and that “helps humans distinguish threatening stimuli from safe stimuli the next day. So while animal studies focused on learning and unlearning a threat, our study showed REM sleep in humans is more related to learning and remembering safety.”
He noted, however, that the findings are not conclusive. No comparable animal studies, for example, have examined the relationship between safety and REM sleep. Nonetheless, the findings do encourage further investigation, eventually into human PTSD populations where fear, safety and sleep are on-going and paramount concerns among military veterans and others.
“A very large percentage of missions in both Iraq and Afghanistan were at night,” said Drummond, who is also associate director of the Mood Disorders Psychotherapy Program at VA San Diego Healthcare System. “So soldiers learned the night was a time of danger. When they come home, they have a hard time learning night here is a time to relax and go to sleep.”
McLean Hospital researchers are reporting that xenon gas, used in humans for anesthesia and diagnostic imaging, has the potential to be a treatment for post-traumatic stress disorder (PTSD) and other memory-related disorders.
“In our study, we found that xenon gas has the capability of reducing memories of traumatic events,” said Edward G. Meloni, PhD, assistant psychologist at McLean Hospital and an assistant professor of Psychiatry at Harvard Medical School. “It’s an exciting breakthrough, as this has the potential to be a new treatment for individuals suffering from PTSD.”
In the study, published in the current issue of PLOS ONE, Meloni, and Marc J. Kaufman, PhD, director of the McLean Hospital Translational Imaging Laboratory, examined whether a low concentration of xenon gas could interfere with a process called reconsolidation – a state in which reactivated memories become susceptible to modification. “We know from previous research that each time an emotional memory is recalled, the brain actually restores it as if it were a new memory. With this knowledge, we decided to see whether we could alter the process by introducing xenon gas immediately after a fear memory was reactivated,” explained Meloni.
The investigators used an animal model of PTSD called fear-conditioning to train rats to be afraid of environmental cues that were paired with brief footshocks. Reactivating the fearful memory was done by exposing the rats to those same cues and measuring their freezing response as a readout of fear. “We found that a single exposure to the gas, which is known to block NMDA receptors involved in memory formation in the brain, dramatically and persistently reduced fear responses for up to 2 weeks. It was as though the animals no longer remembered to be afraid of those cues”, said Dr. Meloni.
Meloni points out that the inherent properties of a gas such as xenon make it especially attractive for targeting dynamic processes such as memory reconsolidation. “Unlike other drugs or medications that may also block NMDA receptors involved in memory, xenon gets in and out of the brain very quickly. This suggests that xenon could be given at the exact time the memory is reactivated, and for a limited amount of time, which may be key features for any potential therapy used in humans.”
“The fact that we were able to inhibit remembering of a traumatic memory with xenon is very promising because it is currently used in humans for other purposes, and thus it could be repurposed to treat PTSD,” added Kaufman.
For these investigators, several questions remain to be addressed with further testing. “From here we want to explore whether lower xenon doses or shorter exposure times would also block memory reconsolidation and the expression of fear. We’d also like to know if xenon is as effective at reducing traumatic memories from past events, so-called remote memories, versus the newly formed ones we tested in our study”.
Meloni and Kaufman indicate that future studies are planned to test if the effects of xenon in rats seen in their study translate to humans. Given that intrusive re-experiencing of traumatic memories – including flashbacks, nightmares, and distress and physiological reactions induced when confronted with trauma reminders – is a hallmark symptom for many who suffer from PTSD, a treatment that alleviates the impact of those painful memories could provide welcome relief.
Marijuana compound may offer treatment for Alzheimer’s disease
Extremely low levels of the compound in marijuana known as delta-9-tetrahydrocannabinol, or THC, may slow or halt the progression of Alzheimer’s disease, a recent study from neuroscientists at the University of South Florida shows.
Researchers from the USF Health Byrd Alzheimer’s Institute showed that extremely low doses of THC reduce the production of amyloid beta, found in a soluble form in most aging brains, and prevent abnormal accumulation of this protein — a process considered one of the pathological hallmarks evident early in the memory-robbing disease. These low concentrations of THC also selectively enhanced mitochondrial function, which is needed to help supply energy, transmit signals, and maintain a healthy brain.
“THC is known to be a potent antioxidant with neuroprotective properties, but this is the first report that the compound directly affects Alzheimer’s pathology by decreasing amyloid beta levels, inhibiting its aggregation, and enhancing mitochondrial function,” said study lead author Chuanhai Cao, PhD and a neuroscientist at the Byrd Alzheimer’s Institute and the USF College of Pharmacy.
“Decreased levels of amyloid beta means less aggregation, which may protect against the progression of Alzheimer’s disease. Since THC is a natural and relatively safe amyloid inhibitor, THC or its analogs may help us develop an effective treatment in the future.”
The researchers point out that at the low doses studied, the therapeutic benefits of THC appear to prevail over the associated risks of THC toxicity and memory impairment.
Neel Nabar, a study co-author and MD/PhD candidate, recognized the rapidly changing political climate surrounding the debate over medical marijuana.
“While we are still far from a consensus, this study indicates that THC and THC-related compounds may be of therapeutic value in Alzheimer’s disease,” Nabar said. “Are we advocating that people use illicit drugs to prevent the disease? No. It’s important to keep in mind that just because a drug may be effective doesn’t mean it can be safely used by anyone. However, these findings may lead to the development of related compounds that are safe, legal, and useful in the treatment of Alzheimer’s disease.”
The body’s own system of cannabinoid receptors interacts with naturally-occurring cannabinoid molecules, and these molecules function similarly to the THC isolated from the cannabis (marijuana) plant.
Dr. Cao’s laboratory at the Byrd Alzheimer’s Institute is currently investigating the effects of a drug cocktail that includes THC, caffeine as well as other natural compounds in a cellular model of Alzheimer’s disease, and will advance to a genetically-engineered mouse model of Alzheimer’s shortly.
“The dose and target population are critically important for any drug, so careful monitoring and control of drug levels in the blood and system are very important for therapeutic use, especially for a compound such as THC,” Dr. Cao said.
Scientists Uncover Navigation System Used by Cancer, Nerve Cells
Duke University researchers have found a ”roving detection system” on the surface of cells that may point to new ways of treating diseases like cancer, Parkinson’s disease and amyotrophic lateral sclerosis (ALS).
The cells, which were studied in nematode worms, are able to break through normal tissue boundaries and burrow into other tissues and organs — a crucial step in many normal developmental processes, ranging from embryonic development and wound-healing to the formation of new blood vessels.
But sometimes the process goes awry. Such is the case with metastatic cancer, in which cancer cells spread unchecked from where they originated and form tumors in other parts of the body.
“Cell invasion is one of the most clinically relevant yet least understood aspects of cancer progression,” said David Sherwood, an associate professor of biology at Duke.
Sherwood is leading a team that is investigating the molecular mechanisms that control cell invasion in both normal development and cancer, using a one-millimeter worm known as C. elegans.
At one point in C. elegans development, a specialized cell called the anchor cell breaches the dense, sheet-like membrane that separate the worm’s uterus from its vulva, opening up the worm’s reproductive tract.
Anchor cells can’t see, so they need some kind of signal to tell them where to break through. In a 2009 study, Sherwood and colleagues discovered that an extracellular cue called netrin orients the anchor cell so that it invades in the right direction.
In a new study appearing Aug. 25 in the Journal of Cell Biology, the team shows how receptors on the invasive cells essentially rove around the cell membrane ”hunting” for the missing netrin signal that will guide the cell to the correct location.
The researchers used a video camera attached to a powerful microscope to take time-lapse movies of the slow movement of the C. elegans anchor cell during its invasion (Figure 1, Figure 2).
Their time-lapse analyses reveal that when netrin production is blocked, netrin receptors on the surface of the anchor cell periodically cluster, disperse and reassemble in a different region of the cell membrane. The receptors cluster alongside patches of actin filaments — thin flexible fibers that help cells change shape and form invasive protrusions –- that pop up in each new spot.
“It’s kind of like a missile detection system,” Sherwood said.
Rather than the whole cell having to move around, its receptors move around on the outside of the cell until they get a signal. Once the receptors locate the netrin signal, they stabilize in the region of the cell membrane that is closest to the source of the signal.
The findings redefine decades-old ideas about how the cell’s navigation system works. “Cells don’t just passively respond to the netrin signal — they’re actively searching for it,” Sherwood said.
Given that netrin has been found to promote cell invasion in some of the most lethal cancers, the findings could lead to new treatment strategies. Disrupting the cell’s netrin detection system, for example, could prevent cancer cells from finding their way to the bloodstream or the lymphatic system and stop them from metastasizing, or becoming invasive and spreading throughout the body.
“One of the things we’re gearing up to do next are drug screens with our collaborators to see if we can block this detection system during invasion,” Sherwood said.
Scientists have also known for years that netrin plays a key role in wiring the brain and nervous system by guiding developing nerve cells as they grow and form connections.
This means the results could also point to new ways of treating neurological disorders like Parkinson’s and ALS and recovering from spinal cord injuries.
Tinkering with the cell’s netrin detection machinery, for example, may make it possible to encourage damaged cells in the central nervous system — which normally have limited ability to regenerate — to regrow.
Changes in the eye can predict changes in the brain
Researchers at the Gladstone Institutes and University of California, San Francisco have shown that a loss of cells in the retina is one of the earliest signs of frontotemporal dementia (FTD) in people with a genetic risk for the disorder—even before any changes appear in their behavior.
Published today in the Journal of Experimental Medicine, the researchers, led by Gladstone investigator Li Gan, PhD and UCSF associate professor of neurology Ari Green, MD, studied a group of individuals who had a certain genetic mutation that is known to result in FTD. They discovered that before any cognitive signs of dementia were present, these individuals showed a significant thinning of the retina compared with people who did not have the gene mutation.
“This finding suggests that the retina acts as a type of ‘window to the brain,’” said Dr. Gan. “Retinal degeneration was detectable in mutation carriers prior to the onset of cognitive symptoms, establishing retinal thinning as one of the earliest observable signs of familial FTD. This means that retinal thinning could be an easily measured outcome for clinical trials.”
Although it is located in the eye, the retina is made up of neurons with direct connections to the brain. This means that studying the retina is one of the easiest and most accessible ways to examine and track changes in neurons.
Lead author Michael Ward, MD, PhD, a postdoctoral fellow at the Gladstone Institutes and assistant professor of neurology at UCSF, explained, “The retina may be used as a model to study the development of FTD in neurons. If we follow these patients over time, we may be able to correlate a decline in retinal thickness with disease progression. In addition, we may be able to track the effectiveness of a treatment through a simple eye examination.”
The researchers also discovered new mechanisms by which cell death occurs in FTD. As with most complex neurological disorders, there are several changes in the brain that contribute to the development of FTD. In the inherited form researched in the current study, this includes a deficiency of the protein progranulin, which is tied to the mislocalization of another crucial protein, TDP-43, from the nucleus of the cell out to the cytoplasm.
However, the relationship between neurodegeneration, progranulin, and TDP-43 was previously unclear. In follow-up studies using a genetic mouse model of FTD, the scientists were able to investigate this connection for the first time in neurons from the retina. They identified a depletion of TDP-43 from the cell nuclei before any signs of neurodegeneration occurred, signifying that this loss may be a direct cause of the cell death associated with FTD.
TDP-43 levels were shown to be regulated by a third cellular protein called Ran. By increasing expression of Ran, the researchers were able to elevate TDP-43 levels in the nucleus of progranulin-deficient neurons and prevent their death.
“With these findings,” said Dr. Gan, “we now not only know that retinal thinning can act as a pre-symptomatic marker of dementia, but we’ve also gained an understanding into the underlying mechanisms of frontotemporal dementia that could potentially lead to novel therapeutic targets.”
Mouse model for epilepsy, Alzheimer's gives window into the working brain
University of Utah scientists have developed a genetically engineered line of mice that is expected to open the door to new research on epilepsy, Alzheimer’s and other diseases.
The mice carry a protein marker, which changes in degree of fluorescence in response to different calcium levels. This will allow many cell types, including cells called astrocytes and microglia, to be studied in a new way.
"This is opening up the possibility to decipher how the brain works," said Petr Tvrdik, Ph.D., a research fellow in human genetics and a senior author on the study.
The research was published Aug. 14, 2014, in Neuron, a world-leading neuroscience journal. The work is the result of a three-year study involving multiple labs connected with The Brain Institute at the University of Utah. The lead author is J. Michael Gee, who is pursuing both a medical degree and a graduate degree in bioengineering at the university.
"We’re really in the era of team science," said John White, Ph.D., professor of bioengineering, executive director of the Brain Institute and the study’s corresponding author.
With the new mouse line, scientists can use a laser-based fluorescence microscope to study the calcium indicator in the glial cells of the living mouse, either when the mouse is anesthetized or awake. Calcium is studied because it is an important signaling molecule in the body and it can reveal how well the brain is functioning.
Using this method, the scientists are essentially creating a window into the working brain to study the interactions between neurons, astrocytes and microglia.
"We believe this will give us new insights for treatments of epilepsy and for new views of how the immune system of the brain works," White said.
About one-third of the 3 million Americans estimated to have epilepsy lack adequate treatment to manage the disease.
Describing a long-standing collaboration with fellow university researcher and professor of pharmacology and toxicology Karen Wilcox, Ph.D., White said, “We believe the glial cells are malfunctioning in epilepsy. What we’re trying to do is find out in what ways astrocytes participate in the disease.”
This research is expected to lead to new classes of drugs.
The ability to track calcium changes in microglial cells will also open up the possibility of studying inflammatory diseases of the brain. Every neurological disease, including Multiple Sclerosis and Alzheimer’s, appears to include components of inflammation, the scientists said.
"Live imaging and monitoring microglial activity and responses to inflammation was not possible before," said Tvrdik, particularly in living animals. In the past, researchers studied post-mortem tissue or relied on invasive approaches using synthetic dyes.
Study of self-awareness in MS has implications for rehabilitation
A new study of self-awareness by Kessler Foundation researchers shows that persons with multiple sclerosis (MS) may be able to improve their self-awareness through task-oriented cognitive rehabilitation. The study was epublished ahead of print on July 2 in NeuroRehabilitation. Self-awareness is one’s ability to recognize cognitive problems caused by brain injury. This is the first study of self-awareness in MS that includes assessment of online awareness, as well as metacognitive awareness.
Yael Goverover, PhD, OT, is a visiting scientist at Kessler Foundation. She is an associate professor at New York University. Dr. Goverover is a recipient of the National Institute on Disability and Rehabilitation Research Fellowship award (Mary Switzer Award). Drs. Genova, Chiaravalloti and DeLuca are MS researchers at Kessler Foundation.
The researchers assessed 18 people with MS and 16 healthy controls for 2 types of self-awareness - metacognitive knowledge of disabilities (or intellectual awareness) and online awareness (emergent or anticipatory awareness). They also looked at the relationships among self-awareness, functional performance and quality of life (QoL). Assessment involved the Functional Behavior Profile, questionnaires administered before and after functional tasks (purchasing cookies and airline tickets via the Internet) and the Functional Assessment of Multiple Sclerosis measure.
“Results showed that compared with controls, people with MS assessed their actual performance more realistically following completion of a task. This suggests that individuals may be able to improve their self-awareness through more experience with tasks,” noted Nancy Chiaravalloti, PhD, director of Neuropsychology & Neuroscience Research at Kessler Foundation.
"Research that leads to better understanding of types of self-awareness, functional outcomes and QOL will aid the development of effective assessments and rehabilitation interventions,” said Dr. Chiaravalloti. “The association between online awareness and task performance in this study, for example, may have implications for cognitive rehabilitation strategies in the MS population.”