Nav: Home

Astroglia zip the 2 halves of the brain together

October 11, 2016

Scientists have identified the cellular origins of the corpus callosum, the 200 million nerve fibers that connect the two hemispheres of the brain. A study of mice and human brains published on October 11 in Cell Reports shows that during development, astroglia, the main supporting cells of the brain, weave themselves between the right and left lobes, and form the bridge for axons to grow across the gap. Without these astroglia, the corpus callosum doesn't form correctly, causing a condition called callosal agenesis--which affects 1 out of 4,000 people--and a range of developmental disorders.

"Very little is known about the cause of callosal agenesis, and there hasn't been a satisfactory explanation for how it occurs," says first author Ilan Gobius, a postdoctoral research fellow at the Queensland Brain Institute, University of Queensland in Australia. "We believe we've finally discovered one of the major causes for this group of disorders."

During development, the hemispheres of the brain are separated by a gap filled with fibroblasts--and other non-neural cells. In order to see how callosal axons navigated around this area to connect the hemispheres, the researchers used mice embryos to observe the growth of individual axons. They observed that the axons cannot grow through this gap, and instead grow down and around it to connect the two hemispheres of the brain. However, they don't do this on their own; instead they rely on astroglial cells to guide their path.

Using the mice embryos and human brain scans, the team lead by Linda Richards, Deputy Director of the Queensland Brain Initiative found that these astroglial cells are initially located beneath the area filled with fibroblasts, but during fetal development a molecular pathway signals the astroglia to migrate forward and mature, allowing them to weave together into a thick column along the center of the brain, which pushes back against the gap and causes it to shrink. This column of astroglia acts as a bridge for callosal axons and allows them to cross between the two sides of the brain. As this bridge grows, the gap between the hemispheres shrinks until only a small portion of it remains, and the corpus callosum begins to form.

The researchers saw that when there was an issue with molecular signaling, the astroglial cells didn't change into multipolar cells. This prevented the formation of the callosal tract and resulted in callosal agenesis. "This midline area is one of the first places in the brain that you normally start to see these astroglial cell changes," says Gobius. "And we found that if these cells don't make this transition, the remodeling process that you need to form the corpus callosum doesn't get started."

Moving forward, the team hopes to use this knowledge to help make better diagnostic tests for callosal agenesis. As of now, doctors can only diagnose the disorder during fetal development using an ultrasound or MRI, but since the condition can range in severity, the lack of an accurate genetic test makes it difficult to council parents about what developmental issues to expect in their child.

"The field is desperate for a genetic test for this disorder," says Richards. "This opens up the possibility for testing for genes like those that Dr. Gobius identified. Identifying the cellular process that causes this range of disorders is very important for looking to the future and finding new genes for possible therapeutic targets."
This work was supported by research grants from the Australian National Health and Medical Research Council, the Australian Research Council and the National Institutes of Health, USA and was performed at the Queensland Brain Institute at The University of Queensland, the Departments of Neurology, Psychiatry, Radiology and Biomedical Imaging at the University of California San Francisco, the National Centre for Medical Genetics at Our Lady's Hospital for Sick Children, and the Center for Integrative Brain Research at the Seattle Children's Research Institute.

Cell Reports Gobius, Morcom, Suárez, Bunt, Richards, et al: "Astroglial-mediated remodeling of the interhemispheric midline is required for the formation of the corpus callosum"

Cell Reports (@CellReports), published by Cell Press, is a weekly open-access journal that publishes high-quality papers across the entire life sciences spectrum. The journal features reports, articles, and resources that provide new biological insights, are thought-provoking, and/or are examples of cutting-edge research. Visit: To receive Cell Press media alerts, contact

Cell Press

Related Brain Articles:

Study describes changes to structural brain networks after radiotherapy for brain tumors
Researchers compared the thickness of brain cortex in patients with brain tumors before and after radiation therapy was applied and found significant dose-dependent changes in the structural properties of cortical neural networks, at both the local and global level.
Blue Brain team discovers a multi-dimensional universe in brain networks
Using a sophisticated type of mathematics in a way that it has never been used before in neuroscience, a team from the Blue Brain Project has uncovered a universe of multi-dimensional geometrical structures and spaces within the networks of the brain.
New brain mapping tool produces higher resolution data during brain surgery
Researchers have developed a new device to map the brain during surgery and distinguish between healthy and diseased tissues.
Newborn baby brain scans will help scientists track brain development
Scientists have today published ground-breaking scans of newborn babies' brains which researchers from all over the world can download and use to study how the human brain develops.
New test may quickly identify mild traumatic brain injury with underlying brain damage
A new test using peripheral vision reaction time could lead to earlier diagnosis and more effective treatment of mild traumatic brain injury, often referred to as a concussion.
This is your brain on God: Spiritual experiences activate brain reward circuits
Religious and spiritual experiences activate the brain reward circuits in much the same way as love, sex, gambling, drugs and music, report researchers at the University of Utah School of Medicine.
Brain scientists at TU Dresden examine brain networks during short-term task learning
'Practice makes perfect' is a common saying. We all have experienced that the initially effortful implementation of novel tasks is becoming rapidly easier and more fluent after only a few repetitions.
Balancing time & space in the brain: New model holds promise for predicting brain dynamics
A team of scientists has extended the balanced network model to provide deep and testable predictions linking brain circuits to brain activity.
New view of brain development: Striking differences between adult and newborn mouse brain
Spikes in neuronal activity in young mice do not spur corresponding boosts in blood flow -- a discovery that stands in stark contrast to the adult mouse brain.
Map of teenage brain provides evidence of link between antisocial behavior and brain development
The brains of teenagers with serious antisocial behavior problems differ significantly in structure to those of their peers, providing the clearest evidence to date that their behavior stems from changes in brain development in early life, according to new research led by the University of Cambridge and the University of Southampton, in collaboration with the University of Rome Tor Vergata in Italy.

Related Brain Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".