We have all heard of our “little gray cells” and the marvelous things they can do. The neurons in our brain carry action potentials that enable us to perform everyday activities and form complex thoughts.. However, scientists have only recently begun to discover the essential properties of glial cells, the neuron’s lesser known relative.
Glial cells – specifically astrocytes, named for their distinctive “star” pattern – are cells in the brain that perform a variety of functions, such as supporting neurons and providing them with nutrition. The astrocytes’ “spongy” structure acts as a metabolic support system that grows in intricate structures around synapses. While astrocytes have been around for as long as the brain has, scientists have long dismissed glial cells as simple structural cells that serve an important purpose, but not complex ones capable of contributing to higher level thinking.
A 2017 study conducted at Duke University has proved past scientists wrong, finding that astrocytes may serve a much larger purpose in brain development than previously thought. They may even play a role in synaptic remodeling and development. Cagla Eroglu, an associate professor of cell biology and neurobiology at Duke University, and her associate Nicola J. Allen, a glial biologist, state:
“Despite the clear importance of astrocytes for the establishment and maintenance of proper synaptic connectivity, our understanding of their role in brain function is still in its infancy. We propose that this is at least in part due to large gaps in our knowledge of the cell biology of astrocytes and the mechanisms they use to interact with synapses.”
To bridge the knowledge gap between astrocytes and their effects on synapses, the team started their research by looking at the formation of astrocytes. Eroglu and her team of researchers discovered that growing astrocytes separately from neurons resulted in stunted growth, while astrocytes grown with neurons resulted in them developing their distinctive elaborate structures. The astrocytes would build off of the neuron’s structure like scaffolding even if it was dead. These results proved that the astrocytes’ structure is not random- it molds itself uniquely to every neuron thus forming deliberately shaped networks.
Eroglu and Allen continue to say:
“We found that astrocytes’ shape and their interactions with synapses are fundamentally important for brain function and can be linked to diseases in a way that people have neglected until now.”
Eroglu’s research team investigated three different proteins in astrocytes that affected their growth and the complexity of their branching. They found that altering protein production stunted the growth of astrocytes, disrupting the manner in which they insulated synapses. This resulted in a severe disruption of inhibitory and excitatory signals, degrading neural communication. The same disruption of these signals is a common symptom of neurological disorders. With these experimental results, Eroglu’s team concluded that astrocyte dysfunction may be an underlying cause of much larger neuronal disorders, such as autism, schizophrenia and epilepsy.
In their 2017 research paper, Eroglu’s team discuss the correlation between astrocyte dysfunction and various neural disorders. They state that:
“What is striking is that each of these neurodevelopmental disorders is caused by diverse genetic mutations, yet the changes in expression and release of synaptogenic factors from astrocytes is overlapping. This points to a shared defect in astrocyte development across these disorders.”
Furthermore, they also discovered that astrocyte development can be detrimental at two extremes. Whether developing with stunted growth or being overgrown, astrocytes can severely damage neurotransmission either way.
“Importantly, altered synaptogenic potential of astrocytes can either be a deficit, as seen in Fragile X and Down syndrome, or an excess, like in Costello Syndrome. This suggests that the levels of astrocyte synaptogenic proteins, not just their presence or absence, are important regulators of neuronal synaptic development.”
While much is still unknown about the role that astrocytes play in the brain, scientists are now more aware of how glial biology can shed light on confounding neurological disorders. As a largely unexplored branch of neuroscience, astrocyte research has nowhere else to go but up.
Edited by: Madison Hopper
Illustrated by: Haley Pak