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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.”