A study published in Nature Neuroscience has identified the manner in which specific brain cells interact during development stages can be related to neuropsychiatric and neurological disease, some of which manifest later in life.

According to researchers from the University of Colorado School of Medicine, brain functions rely on the distinct formation of millions of links between particular types of cells in the brain, including glial cells and neurons. The scientists studied how a specific kind of connection known as myelination, functions among different cell types and how the nervous system eliminates excess connections.

Bruce Appel, senior author of the study, said in a statement, "We believe these new data will lead to improved understanding of the potential causes for some neurological and neuropsychiatric diseases."

Brain
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Immune Cell's Defense System

Appel and first author Alexandria N. Hughes, a graduate student in the CU Graduate School's Neuroscience Program, used larval zebrafish, small and transparent vertebrates that share many aspects of nervous system development with humans. Because zebrafish larvae are transparent, cells of the nervous system can be watched during the course of development.

The team found that microglia, which are the brain's population of immune cells that defend against infection throughout life, also play an essential role in regulating myelination. Myelination is a connection process formed between electrically active neurons and a glial cell type called oligodendrocytes.

Oligodendrocytes wrap the long axons of neurons with segments of fatty myelin membrane to insulate them, which increases the speed brain signals are sent. The process of how the nervous system removes incorrect myelin segments or sheaths is unknown.

Insights Into Development of Disease

In their study, the CU researchers observed that microglia extend within myelinated tracts of the nervous system and examine individual myelin sheaths, removing some of them by phagocytosis, or cellular "eating." Furthermore, the amount of myelin that microglia ate depended on neuronal activity, suggesting that microglia may listen to neurons to determine whether to remove myelin.

Understanding myelin is important because myelin abnormalities are a hallmark of numerous neurological and neuropsychiatric diseases, including Alzheimer's disease, schizophrenia, and an autism spectrum disorder.

These newly reported data raise the possibility that microglial dysfunction, even early in development, could set the stage for later disease emergence and progression by altering myelination.

"Learning how microglia, oligodendrocytes, and neurons work together to build a functional nervous system could ultimately help our understanding of how these cells interact in diseases of development or aging and may influence strategies for myelin repair," Hughes said.

(With inputs from agencies)