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Neural stem and progenitor cell diversity in brain development may contribute to cortical complexity

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Stem and progenitor cells exhibit diversity in early brain development that likely contributes to later neural complexity in the adult cerebral cortex, a study suggests.

Researchers from the Center for Neuroscience Research (CNR) at Children’s National Hospital say this research expands on existing ideas about brain development, and could significantly impact the clinical care of neurodevelopment diseases in the future. the study was done in collaboration with a research team at Yale University led by Nenad Sestani.

“Our study provides a new glimpse into the landscape of the developing brain. What we are seeing are new complex families of cells very early in development,” says Tarik Haydar, director of CNR at Children’s National, who led this study. “Understanding the role of these cells in forming the cerebral cortex is now possible in a way that wasn’t possible before.”

The cerebral cortex emerges early in development and is the seat of higher-order cognition, social behavior and motor control. While the rich neural diversity of the cerebral cortex and the brain in general is well-documented, how this variation arises is relatively poorly understood.

“We’ve shown in our previous work that neurons generated from different classes of cortical stem and progenitor cells have different functional properties,” says William Tyler, CNR research faculty member and co-first author of the study.

“Part of the reason for doing this study was to go back and try to classify all the different progenitors that exist so that eventually we can figure out how each contributes to the diversity of neurons in the adult brain.”

Using a preclinical model, the researchers were able to identify numerous groups of cortical stem and precursor cells with distinct gene expression profiles. The team also found that these cells showed early signs of lineage diversification likely driven by transcriptional priming, a process by which a mother cell produces RNA for the sole purpose of passing it on to its daughter cells for later protein production.

Using novel trajectory reconstruction methods, the team observed distinct developmental streams linking precursor cell types to particular excitatory neurons. After comparing the dataset of the preclinical model to a human cell database, notable similarities were found, such as the surprising cross-species presence of basal radial glial cells (bRGCs), an important type of progenitor cell previously thought to be found mainly in the primate brain.

“At a very high level, the study is important because we are directly testing a fundamental theory of brain development,” says Zhen Li, CNR research postdoctoral fellow and co-first author of the study. The results add support to the protomap theory, which posits that early stem and progenitor diversity paves the way for later neuronal diversity and cortical complexity. Furthermore the results also hold exciting translational potential.

“There is evidence showing that neurodevelopmental diseases affect different populations of the neural stem cells differently,” says Dr. Li. “If we can have a better understanding of the complexity of these neural stem cells there is huge implication of disease prevention and treatment in the future.”

“If we can understand how this early landscape is affected in disorders, we can predict the resulting changes to the cortical architecture and then very narrowly define ways that groups of cells behave in these disorders,” adds Dr. Haydar. “If we can understand how the cortex normally achieves its complex architecture, then we have key entry points into improving the clinical coruse of a given disorder and improving quality of life.”

Future topics the researchers hope to study include the effects of developmental changes on brain function, the origin and operational importance of bRGCs, and the activity, connections and cognitive features enabled by different families of neurons.

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Abnormal proteins unleash latent toxicity in neurodegenerative diseases

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Most neurological diseases have one thing in common: an accumulation of abnormal proteins around neurons. Researchers agree that these improperly fabricated proteins become progressively more toxic by interacting with healthy proteins, disrupting their functions. This picture, however, may be incomplete, according to a study.

In a recent study published in the Journal of Cell Biology, scientists from Daegu Gyeongbuk Institute of Science and Technology, Korea, have discovered the mechanism of action by which abnormal proteins actually unleash the inherent, but normally latent, toxicity of a natural protein in neurons, causing defects in dendrites (branched parts of a neuron that connect to the next neuron). Therefore, their results provide some clarity as to what actually goes on in diseased neurons. Though the researchers focused on Machado-Joseph disease (MJD), the implications of their results are relevant to other diseases as well.

First, they screened existing data to find candidate genes that were abnormally expressed in MJD patients and mice models. Then, based on the results and using MJD flies as animal models, they identified a problematic transcription factor–a protein that controls and regulates the transcription from DNA of other proteins–called NF-κB. Though this transcription factor is essential for the proper functioning and development of dendrites, the researchers found that something went awry with it when abnormal MJD proteins were around.

Through multiple subsequent experiments, they elucidated a long chain of inhibitory/promoting interactions between native proteins that, at a certain point, clashes with the accumulated abnormal proteins and cascades into a “deregulation” of NF-κB. In turn, this improper regulation unlocks the latent toxicity of NF-κB.

Professor Sung Bae Lee, who led the study, remarks: “Our results open-up a new avenue toward finding cures for neurodegenerative diseases by creating inhibition-based drugs that target improperly regulated latent toxic factors.” Such new potential treatments would directly target the early stages of neuron damage, stopping neurological disorders right on their tracks.

This study lights a beacon of hope for many countries that are struggling to deal with the problems of an aging society. “Korea will become a super-aged society in the near future and establishing an appropriate social system to care for and treat people with neurodegenerative diseases is turning into an urgent social issue,” comments Professor Lee. This might be the first step in a completely new road toward treating these chronic age-related diseases.

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Individualised brain stimulation therapy improves language performance in stroke survivors

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Canadian scientists are pioneering the use of individualised brain stimulation therapy to treat aphasia in recovering stroke patients.

Aphasia is a debilitating language disorder that impacts all forms of verbal communication, including speech, language comprehension, and reading and writing abilities. It affects around one-third of stroke survivors, but can also be present in those with dementia, especially in the form of primary progressive aphasia.

“Aphasia can be very isolating,” says Dr. Jed Meltzer, Baycrest’s Canada Research Chair in Interventional Cognitive Neuroscience and a neurorehabilitation scientist at Baycrest’s Rotman Research Institute (RRI).

“It can negatively affect people’s personal relationships, and it often determines whether or not someone can continue working.”

In a recent study published in the journal Scientific Reports, Dr. Meltzer and his team tested language performance and used magnetoencephalography (MEG) to measure brain waves in 11 stroke survivors with aphasia before and after they underwent brain stimulation therapy.

The scientists found that the participants had abnormal electrical activity in brain regions close to but outside the area destroyed by the stroke. This abnormal activity was mainly a shift to slower brain waves, a pattern they have also observed in individuals with dementia.

“We mapped that abnormal activity and targeted it using non-invasive brain stimulation,” says Dr. Meltzer.

“We found that the stimulation made the activity more normal – that is, faster – and improved language performance in the short term.”

Previous research has demonstrated that brain stimulation can improve language performance in aphasia patients. However, this study is one of the first to link this performance improvement to changes in the brain activity surrounding the tissue destroyed by stroke.

In other words, this study suggests not only that brain stimulation works in aphasia patients, but also that the reason it works may be because it addresses abnormalities in the brain surrounding the destroyed tissue.

Another novel aspect of this work is that the scientists targeted each individual’s abnormal brain activity with the stimulation treatment. In contrast, the standard approach in previous studies has been to use the exact same treatment, targeting the same brain areas, on every patient.

“Our results demonstrate a promising method to personalise brain stimulation by targeting the dysfunctional activity outside of the destroyed brain tissue,” says Dr. Meltzer.

“Aphasia patients are highly variable in terms of where their brain damage is and what part of the brain should be stimulated for therapy. By mapping individuals’ brain waves, we are finding ways to target the right area to improve their language performance.”

While the participants in this study were stroke survivors, individuals with dementia have similar dysfunctional tissue in their brains, and the scientists are also examining the use of brain stimulation in this group.

Dr. Meltzer and his team looked at the immediate effects of single stimulation sessions in this study. As a next step, they have received funding from the Heart and Stroke Foundation to conduct a full-scale clinical trial looking at the longer-term impacts of repeated stimulation for stroke survivors with aphasia.

However, this study has been suspended because of the restrictions on in-person research participation due to the COVID-19 pandemic. In the meantime, the scientists have pivoted to optimize other aspects of aphasia treatment.

With additional funding, the researchers could test different types of stimulation with more patients over more sessions, allowing them to make faster progress in developing this treatment for individuals with aphasia.

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Living with a spinal cord injury and maintaining good mental health during lockdown

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In conjunction with Mental Health Day 2020, Irwin Mitchell organised a webinar offering valuable insights into maintaining good mental health for those affected by Spinal Cord Injury (SCI).

The speakers were a mixture of professionals and people living with a SCI.

Dr Parashar Ramanuj, Consultant Psychiatrist gave an in depth clinical insight as to what a person who has recently sustained an SCI may be dealing with and what ‘coping’ really means

Sophie Lester, a case manager and spinal occupational therapist provided some really helpful guidance on how to maintain good mental health alongside rehabilitation and sustaining a healthy balance.

Ian Younghusband and Anne Luttman-Johnson provided first-hand insight into specific challenges of living with SCI and offered tips, advice and practical strategies to develop coping mechanisms in support of you and/or your loved ones.

The webinar offered some invaluable tips, but after seven months of different degrees of lockdown there were two key points that struck home with me. These were firstly the importance of reaching out to friends, family and charities and secondly keeping to some sort of daily routine and structure which includes hobbies, interests and exercise.

Lockdown was difficult for everyone, but especially for those who were deemed to be high risk. For those living with a SCI, a common cold has the potential to be life threatening. Most people with a SCI live with suppressed immune systems and/or possible respiratory issues, and so the possible impact of coronavirus has the potential to be devastating. Accordingly, people with a SCI were considered to be potentially high risk and were advised to shield.

For anyone who was asked to shield, in order to protect themselves, they were advised to isolate and effectively cut themselves off from their families, support networks and normal daily routines. This would have undoubtedly had an impact upon their mental health and wellbeing.

#TogetherInIsolation

In response to the growing situation, a number of positive and innovative projects have been launched to support the tens of thousands of SCI people who were isolating.

The Spinal Injuries Association (“SIA”) set up a movement, Together in Isolation. The SIA along with other charities and partners, joined forces to support and provide advice to those living with a SCI.

This included weekly inspirational blogs, an online drop-in café at 3pm every Wednesday with SCI Nurse Specialists and Horatio’s Garden providing gardening tips. Back Up, another national SCI charity also set up an online BackUp Lounge for people to just chat.

NeuroKinex is a not for profit organisation which in usual times, provides hands-on activity based rehabilitation for those living with an SCI. They continued to provide therapies and treatment virtually for a number of their clients, providing continuity of their rehabilitation, treatment and routine.

Online accessible experiences

Accessible exercise and fitness and wellness experiences have also become available online, to assist wheelchair users to continue to access exercise from home.

AirBNB launched their ‘experiences’ back in 2017, but when travel had to stop, these converted to virtual experiences with the option of filtering your results to those designed for accessibility. The experiences which have been featured include seated fitness and wellness experiences including Cardiobox, seated adaptive yoga, wheelchair dance and fitness, Mindfulness and Positive thinking with Paralympic heroes. Back Up moved their national wheelchair skills to virtual videos.

Additionally a number of free accessible exercise videos have been shared on social media. Ella, a GB U25 Wheelchair basketball player created Ella’s Wheelchair Workouts, a page on YouTube and Facebook offering and sharing exercise videos to do at home. She does this in conjunction with GymPossible an accessible gym in the North East who then started to produce adaptive fitness videos online.

Looking forward

The last seven months have been tough for everyone, and I am sure that it has had a huge impact on mental health across the country. But I am encouraged by the innovation and sense of community fostered by the use of online and virtual communication which has been sparked by this pandemic, and hope it has assisted some people to be able to continue with accessing their support networks and connecting with others, while participating in their hobbies and exercising from home.

Having access to positive experiences, friendships and exercise virtually when we can’t be there in person helps maintain good mental health. And although it doesn’t replace face to face in person experiences, I am hopeful that this positive community movement continues when life returns to what will be our new ‘normal’.

For those who are interested, I would really recommend watching the webinar recording which gives practical tips and guidance. This can be seen below:


Written by Jessica Bowles, a solicitor specialising in serious injury with a specific interest in Spinal Cord Injuries and rehabilitation at Irwin Mitchell.

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