Neuroscience

Last month, the National Institutes of Health announced a new collaborative initiative that aims to accelerate the search for biomarkers — changes in the body that can be used to predict, diagnose or monitor a disease — in Parkinson’s disease, in part by improving collaboration among researchers and helping patients get involved in clinical studies. As part of this program, launched by the National Institute of Neurological Disorders and Stroke (NINDS), part of the NIH, Clemens Scherzer, MD, a neurologist and researcher at Brigham and Women’s Hospital (BWH), was awarded $2.6 million over five years to work on the development of biomarkers and facilitate NINDS-wide access to one of the largest data and biospecimens bank in the world for Parkinson’s available at BWH. This NINIDS initiative is highlighted in an editorial in the March issue of Lancet Neurology.

"There is a critical gap in the research that leads to lack of treatment for diseases like Parkinson’s," said Scherzer. "Biomarkers are desperately needed to make clinical trials more efficient, less expensive and to monitor disease and treatment response. We are hopeful that this initiative will fast track new discoveries in this area."

According to Scherzer, most of our knowledge of the human brain is based on the analysis of just 1.5 percent of the human genome that encodes proteins. The first part of Scherzer’s project will examine the function of the remaining 98.5 percent of the genome that, so far, has been unexplored in the human brain. While this remainder had been previously dismissed as “junk”, it is now becoming clearer that parts of it actively regulate cell biology.  Scherzer and colleagues believe that “dark matter” RNA transcribed from stretches of so called “junk” DNA is active in brain cells and contributes to the complexity of normal dopamine neurons and, when corrupted, Parkinson’s disease.

"This offers a potentially ground breaking opportunity for biomarker development. Initially, the team will search for these RNAs associated in brain tissue of individuals at earliest stages of the disease. Then, this team will look for related biomarkers in the bloodstream and cerebrospinal fluid in both healthy brains and those with Parkinson’s," Scherzer said.

Scherzer’s lab has been spearheading biomarker research in this field since 2004 and the team already has 2,000 patients enrolled and being followed in a longitudinal study with rich clinical data and one of the largest biobanks in the world for Parkinson’s tissue with support from the Harvard NeuroDiscovery Center. The biobank was designed as an incubator for Parkinson’s research and until now was chiefly available for research collaborations within the Harvard-affiliated community. As part of this new project, this vast resource will be open to all NIH-funded investigators.

"Our ultimate goal is to personalize treatment for our patients with Parkinson’s." said Scherzer. "By opening up this vast collection of specimens, we are exploding the resources that are available to NIH-funded investigators looking at this disease. We hope to harness the power of collaboration to speed up biomarkers discovery."

Researchers from Plymouth University Peninsula Schools of Medicine and Dentistry are part of an international team which has for the first time identified the role of a tumour suppressor in peripheral neuropathy in those suffering multiple tumours of the brain and nervous system.

One in 25,000 people worldwide is affected by neurofibromatosis type 2 (NF2), a condition where the loss of a tumour suppressor called Merlin results in multiple tumours in the brain and nervous system.

Sufferers may experience 20 to 30 tumours at any one time and such numbers often lead to hearing loss, disability and eventually death. Those with NF2 may also experience peripheral neuropathy, which is when the nerves carrying messages to and from the brain and spinal column to the rest of the body do not work.

Peripheral neuropathy leads to further complications for NF2 sufferers, such as pain and numbness, muscle problems, problems with body organs and other symptoms of nerve damage, such as bladder problems, uncontrollable sweating and sexual dysfunction.

Researchers from Plymouth University Peninsula Schools of Medicine and Dentistry are part of an international research team which has for the first time identified the role of a tumour suppressor called Merlin in regulating the integrity of axons. Axons are nerve fibres which transmit information around the body and it is these are that damaged in peripheral neuropathy.

The research team showed that Merlin regulates a protein called neurofilament which supplies structural support for the axon. A better understanding of this mechanism could lead to effective drug therapies to alleviate the symptoms of peripheral neuropathy in patients with NF2.

The results of the research is published this week in Nature Neuroscience.

Researchers at Boston University School of Medicine (BUSM) have, for the first time, identified a specific group of cells in the brainstem whose activation during rapid eye movement (REM) sleep is critical for the regulation of emotional memory processing. The findings, published in the Journal of Neuroscience, could help lead to the development of effective behavioral and pharmacological therapies to treat anxiety disorders, such as post-traumatic stress disorder, phobias and panic attacks.

There are two main stages of sleep – REM and non-REM – and both are necessary to maintain health and to regulate multiple memory systems, including emotional memory. During non-REM sleep, the body repairs tissue, regenerates cells and improves the function of the body’s immune system. During REM sleep, the brain becomes more active and the muscles of the body become paralyzed. Additionally, dreaming generally occurs during REM sleep, as well as physiological events including saccadic eye movements and rapid fluctuations of respiration, heart rate and body temperature. One particular physiological event, which is a hallmark sign of REM sleep, is the appearance of phasic pontine waves (P-waves). The P-wave is a unique brain wave generated by the activation of a group of glutamatergic cells in a specific region within the brainstem called the pons.

Memories of fearful experiences can lead to enduring alterations in emotion and behavior and sleep plays a natural emotional regulatory role after stressful and traumatic events. Persistence of sleep disturbances, particularly of REM sleep, is predictive of developing symptoms of anxiety disorders. A core symptom of these disorders frequently reported by patients is the persistence of fear-provoking memories that they are unable to extinguish. Presently, exposure therapy, which involves controlled re-exposure to the original fearful experience, is considered one of the most effective evidence-based treatments for anxiety disorders. Exposure therapy produces a new memory, called an extinction memory, to coexist and compete with the fearful memory when the fearful cue/context is re-encountered.

The strength of the extinction memory determines the efficacy of exposure therapy. A demonstrated prerequisite for the successful development of an extinction memory is adequate sleep, particularly REM sleep, after exposure therapy. However, adequate or increased sleep alone does not universally guarantee its therapeutic efficacy.

"Given the inconsistency and unpredictability of exposure therapy, we are working to identify which process(es) during REM sleep dictate the success or failure of exposure therapy," said Subimal Datta, PhD, director and principle investigator at the Laboratory of Sleep and Cognitive Neuroscience at BUSM who served as the study’s lead author.

The researchers used contextual fear extinction training, which works to turn off the conditioned fear, to study which brain mechanisms play a role in the success of exposure therapy. The study results showed that fear extinction training increased REM sleep. Surprisingly, however, only 57 percent of subjects retained fear extinction memory, meaning that they did not experience the fear, after 24 hours. There was a tremendous increase of phasic P-wave activity among those subjects. In 43 percent of subjects, however, the wave activity was absent and they failed to retain fear extinction memory, meaning that they re-experienced fear.

"The study results provide direct evidence that the activation of phasic P-wave activity within the brainstem, in conjunction with exposure therapy, is critical for the development of long-term retention of fear extinction memory," said Datta, who also is a professor of psychiatry and neurology at BUSM. In addition, the study indicates the important role that the brainstem plays in regulating emotional memory.

Future research will explore how to activate this mechanism in order to help facilitate the development of new potential pharmacological treatments that will complement exposure therapy to better treat anxiety and other psychological disorders.

According to the National Institute of Mental Health, anxiety disorders affect approximately 40 million American adults each year. While anxiety can sometimes be a normal and beneficial reaction to stress, some people experience excessive anxiety that they are unable to control, which can negatively impact their day to day life.

Reducing fear and stress following a traumatic event could be as simple as providing a protein synthesis blocker to the brain, report a team of researchers from McLean Hospital, Harvard Medical School, McGill University, and Massachusetts General Hospital in a paper published in the March 4 issue of Proceedings of the National Academy of Sciences.

“This is an important basic neuroscience finding that has the potential to have clinical implications for the way individuals with posttraumatic stress disorder are treated,” said Vadim Bolshakov, PhD, director of the Cellular Neurobiology Laboratory at McLean Hospital. “We used a well-known behavioral paradigm that we think models PTSD, fear conditioning, to explore how fearful memories are formed. In our study, the level of fear exhibited by experimental subjects was significantly reduced as a result of decreased signal transfer between cells in the amygdala, a key brain region in fear-related behaviors.”

Influenced by the original findings of Karim Nader, PhD, professor of Psychology at McGill University, whose pioneering work showed that old memories should be un-stored in their brain after their recollection in order to last, Bolshakov’s team exposed rats to auditory stimulus that the animals learned to associate with a mildly traumatic event. After a single exposure to the training procedures, the rats exhibited fear during subsequent exposures to auditory stimuli. The researchers then provided the animals with rapamycin, a protein synthesis blocker, immediately after memory was retrieved in order to control bonding between the cells in the brain. The animals exhibited significantly less fear in response to the fear-invoking stimulus when retested the next day.

“The animals showed stereotypical signs of fear after the initial exposure to the auditory stimulus,” explained Nader, a co-author on the paper. “Following the administration of rapamycin, we show a significant decrease in fear, but not a complete elimination. We were surprised to note that activity between cells was significantly affected by postsynaptic mechanisms.”

The findings of this study, which was funded by a grant from the United States Department of Defense spearheaded by Roger Pitman, suggest that different plasticity rules within cells in the brain are recruited during the formation of the original fear memory and after  fear memory was reactivated.

“Although further work at the molecular level needs to be completed, we are hopeful that this unexpected discovery is the foundation needed to identify ways in which we can better treat anxiety disorders in which fear condition plays a role, such as post-traumatic stress disorder,” said Bolshakov.

A shortage of a protein called TDP-43 caused muscle wasting and stunted nerve cells. This finding supports the idea that malfunction of this protein plays a decisive role in ALS and FTD. The study is published in the “Proceedings of the National Academy of Sciences of the USA" (PNAS).

ALS is an incurable neurological disease which manifests as rapidly progressing muscle wasting. Both limbs and respiratory muscles are affected. This leads to impaired mobility and breathing problems. Patients commonly die within a few years after the symptoms emerged. In rare cases, of which the British physicist Stephen Hawking is the most notable, patients can live with the disease for a long time. In Germany estimates show over 150,000 patients suffering from ALS – an average of 1 in 500 people.

Proteins gone astray

Over the last few years, there has been increasing evidence that ALS and FTD – a form of dementia associated with changes in personality and social behaviour – may have similar or even the same origins. The symptoms overlap and common factors have also been found at the microscopic level. In many cases, particles accumulate and form clumps in the patient’s nerve cells: this applies particularly to the TDP-43 protein.

"Normally, this protein is located in the cell nucleus and is involved in processing genetic information," explains molecular biologist Dr. Bettina Schmid, who works at the DZNE Munich site and at LMU. "However, in cases of disease, TDP-43 accumulates outside the nucleus forming aggregates." Schmid explains that it is not yet clear whether these clumps are harmful. "However, the protein’s normal function is clearly disrupted. It no longer reaches the nucleus to perform its actual task. There seems to be a relationship between this malfunction and the disease."

Studies on zebrafish

However, until now little was known about the function of TDP-43. What are the consequences when this protein becomes non-functional? In order to answer this question, the team led by Bettina Schmid cooperated with the research group of Prof. Christian Haass to investigate the larvae of specially bred zebrafish. Their genetic code had been modified in such a way that no TDP-43 was produced in the organism of the fish. The result: the young fish showed massive muscle wasting and died a few days after hatching. Moreover, the extensions of the nerve cells which control the muscles were abnormal.

"To some extent, these are symptoms typical of ALS and FTD. Therefore, a loss of function of TDP-43 does seem to play a critical role in the disease," says Haass, Site Speaker of the DZNE Munich Site and chair of Metabolic Biochemistry at LMU.

The study revealed one more finding which surprised the researchers: the blood flow of the fish was massively disturbed. “It is well known that circulatory disorders play a part in other forms of dementia, notably in the case of Alzheimer’s,” says Haass. “We now want to investigate whether such problems with blood flow may be a general problem of neurodegenerative diseases and whether such problems occur particularly in patients with ALS and FTD.”