TL;DR

• Amygdala cells linked to anxiety

• Cooperative care influences brain development in humans and marmosets

• Study identifies neural crest stem cells as reprogramming drivers

• Newborns’ brains recognize complex sound patterns

• New blood test shows promise for early Parkinson’s detection

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The global neuroscience market size was valued at USD 28.4 billion in 2016 and it is expected to reach USD 38.9 billion by 2027.

The latest news and research

Measurement of α-synuclein as protein cargo in plasma extracellular vesicles

by David Walt et al. PNAS

Researchers have developed a method to analyze extracellular vesicles (EVs) in blood for early detection of Parkinson’s disease (PD). By isolating EVs and assessing their contents, the team identified a protein called phosphorylated α-synuclein that appears in elevated levels in PD patients.

Brain disorders like Parkinson’s (PD) or Alzheimer’s Disease (AD) start to develop in patients much earlier than when their first clinical symptoms appear. Treating patients at these early stages could slow or even stop their disease, but there is currently no way to diagnose brain disorders at those pre-symptomatic stages.

Thus far, the specific brain lesions caused by PD, for example, can only be detected by analyzing brain biopsies, which can only be obtained posthumously.

To overcome this critical bottleneck, researchers have been pursuing the new concept of “liquid biopsies,” which involves the easy extraction of blood or other body fluids using non-invasive procedures, and analyzing them for molecules originating from brain and other solid tissues.

A particularly promising target in body fluids are “extracellular vesicles” (EVs), tiny membrane-bound sacs released by brain and other cells into their surrounding fluids.

These sacs contain a variety of molecules that can be unique to the cells types that produce them, such as the brain, and thus could also carry protected biomarkers for the early onset of Parkinson’s and other brain diseases.

However, despite recent progress, EV experts haven’t been able to tackle the problem of whether particular biomarker molecules that they measured in isolated EVs are strictly contained inside EVs or non-specifically bound to their surface.

This challenge has actually prevented them from being able to make unambiguous conclusions about cargo molecules in EVs from all types of tissues.

Now, a collaborative team led by David Walt, Ph.D. at the Wyss Institute at Harvard University and Brigham and Women’s Hospital (BWH) in Boston has solved this problem by adding a crucial step to an already validated ultra-sensitive protocol.

By enzymatically digesting all surface-bound proteins from a purified EV population, they were able to specifically home in on cargo protected inside of EVs while eliminating unspecific “contaminations.”

Using their enhanced protocol to measure the PD biomarker ⍺-synuclein in blood, for the first time they were able to accurately determine the small fraction of any protein contained within EVs vs how much of it is present free in total blood plasma.

Importantly, they integrated this advance with a newly developed ultra-sensitive detection assay for a form of ⍺-synuclein that becomes increasingly phosphorylated during the progression of PD and the related condition Lewy Body Dementia.

Analyzing a cohort of patient samples, they could detect an enrichment of the pathological ⍺-synuclein protein inside EVs relative to total plasma. The findings are published in PNAS.

“Research on EVs in our and other groups over the last few decades has steadily advanced our understanding of their complex biology and molecular composition. Yet, the isolation of pure tissue-specific EVs from body fluids like blood or the cerebrospinal fluid surrounding the central nervous system, including the brain, and validating and quantifying their true contents with precise measurements still present formidable technical challenges,” said Wyss Core Faculty member Walt.

“Our recent work is providing a solution to help fill this technological gap, and gets us closer to being able to obtain EVs free from contamination in order to use them as rich sources for clinical biomarkers, as we show with the example of phosphorylated ⍺-synuclein.”

Walt, who is the faculty lead of the Wyss Institute’s Diagnostic Accelerator, is also the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard Medical School (HMS), Professor of Pathology at Brigham and Women’s Hospital, and a Howard Hughes Medical Institute Professor.

Especially motivated by the diagnostic promise of EVs for the early diagnosis of PD, AD, and other brain disorders, the Walt group has been systematically filling vital pieces into this technical jigsaw puzzle.

With philanthropic support from Good Ventures, the Chan Zuckerberg Initiative, and more recently the Michael J. Fox Foundation, they previously developed a technical framework for quantifying EVs and used this quantification to compare EV isolation methods from body fluids.

Their methodology combines a separation technique known as size exclusion chromatography (SEC) to recover most EVs from biofluids with ultra-sensitive “Simoa assays” that allowed them to count single protein molecules associated with EVs that they captured and visualized with specific antibodies.

By now, the team has engineered Simoa assays for a variety of EV-specific biomarkers and, importantly, excluded a widely used candidate surface protein, L1CAM, as a target to isolate brain-specific EVs, which provided the field with an important course correction.

“To answer the conceptually simple but technically challenging question of what percentage of a given protein (such as ⍺-synuclein) present in plasma is inside of EVs relative to outside, we used SEC isolation methods that we previously developed to isolate most EVs from plasma together with an optimized ‘proteinase protection assay’ where we use an enzyme to gently but efficiently chew all proteins off the surface of isolated EVs, while leaving the membrane-enclosed EV interior intact.” said co-first author Dima Ter-Ovanesyan, Ph.D., who is a Senior Scientist at the Wyss Institute and spearheads the EV project with co-first author and Postdoctoral Fellow Tal Gilboa, Ph.D.

Also, to measure ⍺-synuclein at very low levels, Gilboa, together with Postdoctoral Fellow Gina Wang, Ph.D. and Wyss Research Assistant Sara Whiteman in the Walt lab, developed a Simoa assay for ⍺-synuclein that is much more sensitive that any previously reported assay.

Using this assay in their protocol, the team was able to determine that most of the ⍺-synuclein in EVs isolated using their SEC protocol was protected and that this amount presented less than 5% of total blood plasma ⍺-synuclein.

Understanding this amount is particularly important for the eventual goal of measuring ⍺-synuclein in neuron-derived EVs as EVs that originate from a specific tissue like the brain are expected to be rare relative to EVs from blood cells, where ⍺-synuclein is also expressed.

Importantly, in addition to their ultra-sensitive Simoa assay that enabled them to detect the normal unmodified ⍺-synuclein protein, they also developed an assay that is able to detect ⍺-synuclein that becomes phosphorylated at a specific site (pSer129) in the course of PD progression.

“When we applied our advanced methodology to a cohort of blood samples obtained from patients with PD and Lewy Body Dementia as well as healthy control donors, we found that the ratio of phosphorylated ⍺-synuclein relative to total ⍺-synuclein was two to three-fold higher inside EVs relative to outside of EVs,” said Gilboa.

“This was extremely exciting because it suggests that EVs may protect the phosphorylation state of proteins from circulating phosphatases that would otherwise erase this highly informative mark.”

The team is now further exploring whether these assays could be used to differentiate PD patients from people without the disease.

“The work by David Walt’s team presents a technological tour-de-force that brings us closer and closer to a next-generation diagnostic platform with extraordinary potential. At this point, we are not far from using these extremely rich and telling cell-derived vesicles as a window to peak into the brains of patients without requiring surgery,” said Wyss Founding Director Donald Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and Boston Children’s Hospital and the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences.

Translational Insights From Cell Type Variation Across Amygdala Subnuclei in Rhesus Monkeys and Humans

by Drew Fox et al. American Journal of Psychiatry

Researchers have identified specific cell types in the amygdala linked to anxiety, revealing potential new targets for treatment. By analyzing gene expression in human and macaque brains, scientists discovered clusters of cells with unique roles, including “gatekeeper” cells that help control emotional responses.

Treating anxiety, depression and other disorders may depend on the amygdala, a part of the brain that controls strong emotional reactions, especially fear. But a deep understanding of this structure has been lacking.

Now scientists at the University of California, Davis have identified new clusters of cells with differing patterns of gene expression in the amygdala of humans and non-human primates.

The work could lead to more targeted treatments for disorders such as anxiety that affect tens of millions of people.

“The amygdala is central to emotion processing in the brain, and is known to contribute to fear and anxiety,” said Drew Fox, associate professor in the UC Davis Department of Psychology and senior author on the paper.

For that reason, there has long been interest in whether variations in the size or structure of the amygdala are related to disorders such as anxiety and depression. However, it’s increasingly clear that the overall size and structure of the amygdala is not a good predictor of emotional problems in life, Fox said.

Recently, research in rodents has shown that each subregion of the amygdala contains many different cell types with distinct and sometimes opposing functions.

“This suggests that disorders emerge from alterations in specific cell types with distinct roles,” Fox said. However, it is challenging to identify such cell types in humans or other primates, leaving the cellular landscape of the primate amygdala largely unexplored.

To address this critical knowledge gap, graduate student Shawn Kamboj led a collaboration between Fox’s research group and the lab of Professor Cynthia Schumann at the UC Davis School of Medicine to identify cell types in subregions of the human and non-human primate amygdala, based on the genes they express.

This could advance basic research by making it easier to translate results between rodents, non-human primates and humans, and open up new targets for treatment.

The researchers took samples from brains of humans and rhesus macaque monkeys, separated individual cells and sequenced their RNA. This shows which genes are active (being expressed) in a particular cell and allows researchers to sort them into groups based on gene expression.

“We can cluster cells based on their gene expression, identify cell types and their developmental origin,” Fox said.

The researchers searched for specific cell types that expressed the genes implicated in anxiety and other disorders in humans. This strategy can help identify cell types that are most likely to give rise to psychopathology, Fox said.

For example, they identified a specific group of cells that expressed a gene called FOXP2. The new study shows that in humans and macaques, FOXP2 is expressed in cells on the edges of the amygdala, called intercalated cells.

Excitingly, researchers have demonstrated that in rodents, this small group of FOXP2-expressing cells play a role as “gatekeepers,” controlling signal traffic in or out of the amygdala. Together, these data suggest intercalated cells to be a potentially powerful avenue for developing treatments.

The researchers were also able to identify both similarities and differences between cell types in the human and non-human primate amygdala. This is important for understanding how discoveries in animal models of disorders such as anxiety and autism relate to humans.

The approach could help identify cell types as potential drug targets. For example, FOXP2-expressing cells tend to express both anxiety-related genes and a receptor that can be targeted by drugs, called Neuropeptide FF Receptor 2 (NPFFR2).

This result can guide the development of new treatment strategies, by suggesting drugs that activate the NPFFR2 pathway as a potential treatment target in relation to anxiety-related disorders.

Anxiety is a complicated disorder that can present in many different ways. With a better understanding of the cell types involved, it may be possible to identify and target “chokepoints” that affect large numbers of people who experience extreme and debilitating anxiety, Fox said.

“Put simply, if we’re developing a drug to target the amygdala, we want to know which cell type we are targeting,” he said.

Neurodevelopmental timing and socio-cognitive development in a prosocial cooperatively breeding primate (Callithrix jacchus)

by Paola Cerrito et al. Science Advances

Cooperative breeding influences brain development in common marmosets and humans, allowing longer periods for social learning. Marmoset brains, like human brains, develop socio-cognitive regions slowly, maturing in early adulthood. This extended development period supports advanced social skills like prosociality and cooperation. Care from multiple caregivers from birth significantly affects brain structure, shaping socio-cognitive abilities. The findings highlight marmosets as a key model for understanding human social evolution. Insights suggest that early-life social experiences may be central to humans’ unique social behaviors.

The development of primate brains is shaped by various inputs. However, these inputs differ between independent breeders, such as great apes, and cooperative breeders, such as the common marmoset (Callithrix jacchus) and humans. In these species, group members other than the parents contribute substantially to raising the infants from birth onwards.

A group of international researchers led by Paola Cerrito from the University of Zurich’s Department of Evolutionary Anthropology studied how such social interactions map onto brain development in common marmosets.

The study provides new insights into the relationship between the timing of brain development and the socio-cognitive skills of marmosets, in particular their prosocial and cooperative behaviors.

The research team analyzed brain development using magnetic resonance data and showed that in marmosets, the brain regions involved in the processing of social interactions exhibit protracted development — in a similar way to humans.

These brain regions only reach maturity in early adulthood, allowing the animals to learn from social interactions for longer.

Like humans, immature marmosets are surrounded and cared for by multiple caregivers from birth and are therefore exposed to intense social interaction.

Feeding is also a cooperative business: the immature animals are fed by group members and as they get older, they have to beg for food because their mothers are already busy with the next offspring.

According to the study, the need to elicit care from several group members significantly shapes brain development and contributes to the sophisticated socio-cognitive motivation (and observed skills) of these primates.

Given their similarities with humans, marmosets are an important model for studying the evolution of social cognition.

“Our findings underscore the importance of social experiences to the formation of neural and cognitive networks, not only in primates, but also in humans,” explains Cerrito.

The early-life social inputs that characterize infants’ life in cooperatively breeding species may be a driving force in the development of humans’ marked social motivation.

“This insight could have an impact on various fields, ranging from evolutionary biology to neuroscience and psychology,” adds Cerrito.

Neural crest precursors from the skin are the primary source of directly reprogrammed neurons

by Derek van der Kooy et al. StemCell Reports

A team led by researchers at the University of Toronto has discovered that a group of cells located in the skin and other areas of the body, called neural crest stem cells, are the source of reprogrammed neurons found by other researchers.

Their findings refute the popular theory in cellular reprogramming that any developed cell can be induced to switch its identity to a completely unrelated cell type through the infusion of transcription factors. The team proposes an alternative theory: there is one rare stem cell type that is unique in its ability to be reprogrammed into different types of cells.

“We believed that most cases of cell reprogramming could be attributed to a rare, multi-potential stem cell that is found throughout the body and lays dormant within populations of mature cells,” said Justin Belair-Hickey, first author on the study and graduate student of U of T’s Donnelly Centre for Cellular and Biomolecular Research.

“It was not fully understood why reprogramming tends to be an inefficient process. Our data explain this inefficiency by demonstrating that the neural crest stem cell is one of the few stem cells that can produce the desired reprogrammed cell type.”

Neural crest cells, which can be found below the hair follicle in the skin, are genetically predisposed to develop into neurons. This is not unexpected, as many cell types in the skin originate from the same location in the embryo as neurons: the ectodermal germ layer. The ectoderm is the outermost of the three layers of cells that form during embryonic development.

The team was driven to conduct this study through their own questioning of how experimental data from cellular reprogramming research is interpreted in terms of how flexible the identity of a cell is.

This includes theories of how mature cells from one embryonic layer can be directly reprogrammed to mature cells of another embryonic layer, even though the three germ layers are separated by different developmental histories.

They hypothesized that cellular reprogramming can only occur from a stem cell to a mature cell, where both come from the same germ layer.

“I think claims about direct reprogramming are either overstated or based on inaccurate interpretations of the data,” said Belair-Hickey.

“We set out to demonstrate that the identity of a cell is much more defined and stable than the field of cellular reprogramming has proposed. At first glance, it appears that we’ve found skin cells that can be reprogrammed into neurons, but what we’ve actually found are stem cells in the skin that are derived from the brain.”

Neural crest stem cells are found throughout the body, including in skin, bone and connective tissue. Their distribution throughout the body, ability to be reprogrammed into many types of cells and accessibility within the skin for collection makes them a high-potential candidate for stem cell transplantation to treat disease.

“Neural crest stem cells may have gone unnoticed by others studying cell reprogramming because, while they are widespread throughout the body, they are also rare,” said Derek van der Kooy, principal investigator on the study and professor of molecular genetics at the Donnelly Centre and U of T’s Temerty Faculty of Medicine.

“As such, they may have been mistaken for mature cells of various types of tissue that could be reprogrammed into other cell types. I think what we’ve found is a unique group of stem cells that can be studied to understand the true potential of cell reprogramming.”

Functional reorganization of brain regions supporting artificial grammar learning across the first half year of life

by Simon Townsend et al. PLOS Biology

A team of researchers, including psycholinguist Jutta Mueller from the University of Vienna, has discovered that newborns are capable of learning complex sound sequences that follow language-like rules.

This groundbreaking study provides long-sought evidence that the ability to perceive dependencies between non-adjacent acoustic signals is innate.

It has long been known that babies can learn sequences of syllables or sounds that directly follow one another. However, human language often involves patterns that link elements which are not adjacent.

For example, in the sentence “The tall woman who is hiding behind the tree calls herself Catwoman,” the subject “The tall woman” is connected to the verb ending “-s,” indicating third-person singular.

Language development research suggests that children begin to master such rules in their native language by the age of two. However, learning experiments have shown that even infants as young as five months can detect rules between non-adjacent elements, not just in language but in non-linguistic sounds, such as tones.

“Even our closest relatives, chimpanzees, can detect complex acoustic patterns when embedded in tones,” says co-author Simon Townsend from the University of Zurich.

Although many previous studies suggested that the ability to recognize patterns between non-adjacent sounds is innate, there was no clear-cut evidence — until now.

The international team of researchers has provided this evidence by observing the brain activity of newborns and six-month-old infants as they listened to complex sound sequences. In their experiment, newborns — just a few days old — were exposed to sequences where the first tone was linked to a non-adjacent third tone.

After only six minutes of listening to two different types of sequences, the babies were presented with new sequences that followed the same pattern but at a different pitch. These new sequences were either correct or contained an error in the pattern.

Using near-infrared spectroscopy to measure brain activity, the researchers found that the newborns’ brains could distinguish between the correct and incorrect sequences.

“The frontal cortex — the area of the brain located just behind the forehead — played a crucial role in newborns,” explains Yasuyo Minagawa from Keio University in Tokyo.

The strength of the frontal cortex’s response to incorrect sound sequences was linked to the activation of a predominantly left-hemispheric network, which is also essential for language processing.

Interestingly, six-month-old infants showed activation in this same language-related network when distinguishing between correct and incorrect sequences.

The researchers concluded that complex sound patterns activate these language-related networks from the very beginning of life. Over the first six months, these networks become more stable and specialized.

“Our findings demonstrate that the brain is capable of responding to complex patterns, like those found in language, from day one,” explains Jutta Mueller from the University of Vienna’s Department of Linguistics.

“The way brain regions connect during the learning process in newborns suggests that early learning experiences may be crucial for forming the networks that later support the processing of complex acoustic patterns.”

These insights are key to understanding the role of environmental stimulation in early brain development. This is especially important in cases where stimulation is lacking, inadequate, or poorly processed, such as in premature babies.

The researchers also highlighted that their findings show how non-linguistic acoustic signals, like the tone sequences used in the study, can activate language-relevant brain networks.

This opens up exciting possibilities for early intervention programs, that could, for example, use musical stimulation to foster language development.

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