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illustration of the brain

New research provides glimpse into landscape of the developing brain

illustration of the brain

Stem and progenitor cells exhibit diversity in early brain development that likely contributes to later neural complexity in the adult cerebral cortex, this according to a new study in Science Advances. This research expands on existing ideas about brain development, and could significantly impact the clinical care of neurodevelopmental diseases in the future.

Stem and progenitor cells exhibit diversity in early brain development that likely contributes to later neural complexity in the adult cerebral cortex, this according to a study published Nov. 6, 2020, in Science Advances. 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 neurodevelopmental diseases in the future. The study was done in collaboration with a research team at Yale University led by Nenad Sestan, M.D, Ph.D.

“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, Ph.D., 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, Ph.D., 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.

Tarik Haydar

“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, Ph.D., 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.”

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, Ph.D., 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 course 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.

illustration of brain showing cerebellum

NIH grant supports research on locomotor dysfunction in Down Syndrome

illustration of brain showing cerebellum

The National Institutes of Health (NIH) has granted the Children’s National Research Institute (CNRI) nearly $500,000 to better understand and identify specific alterations in the circuitry of the cerebellum that results in locomotor dysfunction in down syndrome.

Down syndrome (DS), the most commonly diagnosed chromosomal condition, affects a range of behavioral domains in children including motor and cognitive function. Cerebellar pathology has been consistently observed in DS, and is thought to contribute to dysfunction in locomotor and adaptive motor skills. However, the specific neural pathways underlying locomotor learning that are disrupted in DS remain poorly understood.

The National Institutes of Health (NIH) has granted the Children’s National Research Institute (CNRI) nearly $500,000 through their NIH-wide initiative INCLUDE – INvestigating Co-occurring conditions across the Lifespan to Understand Down syndrome – to better understand and identify specific alterations in the circuitry of the cerebellum that results in locomotor dysfunction in DS. The INCLUDE initiative aims to support the most promising high risk-high reward basic science.

“There is still a lot unknown about Down syndrome, in particular how fundamental cellular and physiological mechanisms of neural circuit function are altered in this syndrome,” says Vittorio Gallo, Ph.D., chief research officer at Children’s National Hospital and scientific director of CNRI. “Grant funding is particularly important to have the resources to develop and apply new cutting-edge methodology to study this neurodevelopmental disorder.”

The main goal of this research is to identify specific alterations in the circuitry of the cerebellum that result in locomotor dysfunction in DS. Defining specific abnormalities in motor behavior, and identifying the brain regions and neurons which are functionally involved will provide the basis for developing potential therapies for treating motor problems in individuals with DS.

“The last decade has brought rapid advances in neurotechnology to address questions at the ‘systems-level’ understanding of brain function,” says Aaron Sathyanesan, Ph.D., a Children’s National postdoctoral research fellow. “This technology has rarely been applied to preclinical models of neurodevelopmental disorders, and even more rarely to models of Down syndrome.”

An example is the use of fiber-optics to probe changes in neural circuitry during behavior. Using this technology, researchers can now directly correlate the changes in circuitry to deficits in behavior.

“Along with the other approaches in our proposal, this represents the synthesis of a new experimental paradigm that we hope will push the field forward,” says Dr. Sathyanesan.

In 1960, the average life expectancy of a baby with Down syndrome was around 10 years. Today, that life expectancy has increased to more than 47 years. That significant increase reflects critical advances in medicine, however, kids with DS still live with long-term challenges in motor and cognitive ability.

Children’s National strongly supports translation and innovation, and recently recruited internationally renowned DS researcher, Tarik Haydar, Ph.D., as its new director of the Center for Neuroscience Research.

“We’re building significant strength in this area of research. This grant helps open new avenues of investigation to define which cells and circuits are impacted by this common neurodevelopmental disorder,” says Dr. Gallo. “Our cutting-edge approach will help us answer questions that we could not answer before.”

Illustration of brain hemispheres

Children use both brain hemispheres to understand language

Illustration of brain hemispheres

New research finds young children process language in both hemispheres of the brain, which could help compensation after a neural injury. This is unlike adults who process most language tasks in one side (usually the left) of their brain’s two hemispheres. It suggests a possible reason why children often seem to recover from brain injury more easily than adults.

New research finds young children process language in both hemispheres of the brain, which could help compensate after a neural injury. The study, published Sept. 8, 2020, in PNAS, says this is unlike adults who process most language tasks in one side (usually the left) of their brain’s two hemispheres. It suggests a possible reason why children often seem to recover from brain injury more easily than adults.

We talked with researcher William D. Gaillard, M.D., chief of the Divisions of Child Neurology, Epilepsy and Neurophysiology at Children’s National Hospital, to discuss the importance of this work.

Q: Tell us a little bit about this study.

A: This is a study we did with our colleagues at Georgetown University Medical Center, using fMRI to map brain regions that are used to process language across development. What we found was that younger children have more bilateral “activation” in language processing regions, the traditional left and homotopic regions in the right. With aging there is consolidation that becomes more left lateralized. This process is most clearly seen in the frontal brain regions, called Broca’s area, where the right activation diminishes over age

Q: Why are these findings important?

A: It’s important because this work provides evidence for how cognitive systems, and the neural networks that underlie them, become consolidated and lateralized over time during development. It provides insights into principles of the development of cognitive systems.

The timeline for lateralization of language systems means that the cognitive systems that sustain language are “plastic” – that is the right hemisphere can sustain language functions in the setting of injury to the left hemisphere until around 10 years of age.

Q: What excites you about this work?

A: This is part of a larger collaborative effort that is mapping out the consolidation of cognitive systems across development (language, visual spatial, memory and working memory). This work will help us to understand the limits of brain plasticity in the setting of injury caused by stroke or epilepsy, which could have benefits down the road to helping patients recover from these types of events.

Q: How is Children’s National leading the ongoing discovery in this space?

A: It is a true team effort. We are working with colleagues at Georgetown University Medical Center, MedStar National Rehabilitation Network and Johns Hopkins Medicine. Team members come from diverse backgrounds and scientific skills. We are one of the leading groups using advanced functional imaging to investigate brain development of critical cognitive systems and their response to brain injury.

You can find the full study published in PNAS. Learn more about the Children’s National Research Institute Center for Neuroscience Research.

 

Nobuyuki Ishibashi

Cortical dysmaturation in congenital heart disease

Nobuyuki Ishibashi

On Jan. 4, 2019, Nobuyuki Ishibashi, M.D., the director of the Cardiac Surgery Research Laboratory and an investigator with the Center for Neuroscience Research at Children’s National Health System, published a review in Trends in Neurosciences about the mechanisms of cortical dysmaturation, or disturbances in cortical development, that can occur in children born with congenital heart disease (CHD). By understanding the early-life impact and relationship between cardiac abnormalities and cortical neuronal development, Dr. Ishibashi and the study authors hope to influence strategies for neonatal neuroprotection, mitigating the risk for developmental delays among CHD patients.

Dr. Ishibashi answers questions about this review and CHD-neurodevelopmental research:

  1. Tell us more about your research. Why did you choose to study these interactions in this patient population?

My research focuses on studying how CHD and neonatal cardiac surgery affect the rapidly-developing brain. Many children with CHD, particularly the most complex anomalies, suffer from important behavioral anomalies and neurodevelopmental delays after cardiac surgery. As a surgeon scientist, I want to optimize treatment strategy and develop a new standard of care that will reduce neurodevelopmental impairment in our patients.

  1. How does this study fit into your larger body of work? What are a few take-home messages from this paper?

Our team and other laboratories have recently identified a persistent perinatal neurogenesis that targets the frontal cortex – the brain area responsible for higher-order cognitive functions. The main message from this article is that further understanding of the cellular and molecular mechanisms underlying cortical development and dysmaturation will likely help to identify novel strategies to treat and improve outcomes in our patients suffering from intellectual and behavioral disabilities.

  1. What do you want pediatricians and researchers to know about this study? Why is it important right now?

Although the hospital mortality risk is greatly reduced, children with complex CHD frequently display subsequent neurological disabilities affecting intellectual function, memory, executive function, speech and language, gross and fine motor skills and visuospatial functions. In addition to the impact of the neurological morbidity on the patients themselves, the toll on families and society is immense. Therefore it is crucial to determine the causes of altered brain maturation in CHD.

  1. How do you envision this research influencing future studies and pediatric health outcomes? As a researcher, how will you proceed?

In this article we placed special emphasis on the need for well-designed preclinical studies to define disturbances in cortical neurogenesis due to perinatal brain injury. I believe that further study of the impact of hypoxemia on brain development is of broad relevance — not just for children with congenital heart disease, but for other populations where intellectual and behavioral dysfunctions are a source of chronic morbidity, such as survivors of premature birth.

  1. What discoveries do you envision being at the forefront of this field?

One of the important questions is: During which developmental period, prenatal or postnatal, is the brain most sensitive to developmental and behavioral disabilities associated with hypoxemia? Future experimental models will help us study key effects of congenital cortical development anomalies on brain development in children with CHD.

  1. What impact could this research make? What’s the most striking finding and how do you think it will influence the field?

Although cortical neurogenesis at fetal and adult stages has been widely studied, the development of the human frontal cortex during the perinatal period has only recently received greater attention as a result of new identification of ongoing postnatal neurogenesis in the region responsible for important intellectual and behavioral functions. Children’s National is very excited with the discoveries because it has opened new opportunities that may lead to regeneration and repair of the dysmature cortex. If researchers identify ways to restore endogenous neurogenic abilities after birth, the risk of neurodevelopment disabilities and limitations could be greatly reduced.

  1. Is there anything else you would like to add that we didn’t ask you about? What excites you about this research?

In this article we highlight an urgent need to create a truly translational area of research in CHD-induced brain injury through further exploration and integration of preclinical models. I’m very excited about the highly productive partnerships we developed within the Center for Neuroscience Research at Children’s National, led by an internationally-renowned developmental neuroscientist, Vittorio Gallo, Ph.D., who is a co-senior author of this article. Because of our collaboration, my team has successfully utilized sophisticated and cutting-edge neuroscience techniques to study brain development in children born with CHD. To determine the causes of altered brain maturation in congenital heart disease and ultimately improve neurological function, we believe that a strong unity between cardiovascular and neuroscience research must be established.

Additional study authors include Camille Leonetti, Ph.D., a postdoctoral research fellow with the Center for Neuroscience Research and Children’s National Heart Institute, and Stephen Back, M.D., Ph.D., a professor of pediatrics at Oregon Health and Science University.

The research was supported by multiple grants and awards from the National Institutes of Health, inclusive of the National Heart Lung and Blood Institute (RO1HL139712), the National Institute of Neurological Disorders and Stroke (1RO1NS054044, R37NS045737, R37NS109478), the National Institute on Aging (1RO1AG031892-01) and the National Institute of Child Health and Human Development (U54HD090257).

Additional support for this review was awarded by the American Heart Association (17GRNT33370058) and the District of Columbia Intellectual and Developmental Disabilities Research Center, which is supported through the Eunice Kennedy Shriver National Institute of Child Health and Human Development program grant 1U54HD090257.