Radial glia: what is it and what functions does it have in the brain?

Thinking about the brain or the nervous system in general is equivalent to thinking about neurons. And it is that the neuron is the basic unit of the nervous system, which is why we usually focus on them when we are exploring the functioning of said system. But in the brain there are not only neurons. We can also find glial cells, which support, protect and keep neurons alive. Among the multiple types of glial cells that we can find, in this article we are going to focus on the so-called radial glia, an essential element for our development.

• Related article: "Glial cells: much more than the glue of neurons"

What are glial cells?

We understand by glia or glial cells to that group of cells derived from the embryonic epithelium that cover the nervous system and form a network of support, protection, nutrition and maintenance of neurons. Initially it was believed that they were a substance that only held neurons together, although this hypothesis was rejected after the discovery of the existence of synapses.

Its functions are multiple: in addition to contributing to provide a structure to the nervous system, it has been observed that they are glial cells which interact between neurons and cells of the cerebrovascular system, acting as filter. This means that the glia can provide nutrients and oxygen to the neurons., something that refers to one of its main and most relevant roles: that of providing nutrients and keeping the nervous system alive. One last especially relevant role of this type of cells is the fact that they eliminate waste and maintain stability in the environment in which the neurons are found.

But while traditionally viewed primarily as supportive, research recent studies propose that they are capable of both uptake and release transmitter substances of information with a possible influence on synaptic transmission that occurs between neurons. Thus, they have an effect on information processing beyond mere neural support.

Glial cells are essential for the proper functioning and survival of the nervous system. But the term glia includes a large number of cell types. Among them we can find astrocytes, oligodendrocytes, the Schwann cells or the one that concerns us in this article, the radial glia.

Radial glia: basic elements

As regards the radial glia, we are before a type of glial cell of generally bipolar morphology that extends throughout the cerebral and cerebellar cortex (although in the latter case there are more elongations, being multipolar). These are cells that serve as a structural pillar and contribute to the development of the nervous system.

They have often been associated with another glial cell type, astrocytes, because they have roles typical of this cell type. glial cells and that, like these, present similar cytoskeletal and membrane proteins (possessing, among other receptors, glutamate or GABA). In fact, the radial glia can become or derive in them.

Radial glia, also called aldainoglia, are known primarily for serving as pathway or guide for neurons during fetal development. Said guide is produced due to the interaction of glia and neuron, through a process of attraction to chemical level and the role of glia in promoting the growth and migration of fibers nervous.

However, this role is reduced with the passage of time: once the migration of the neurons of the cortex has taken place towards their position In the end, and once new neurons stop being born in most areas of the nervous system, their role becomes focused on supporting the network. neural.

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Its most important and well-known functions

The radial glia fulfills different roles within the organism, but the most outstanding, investigated and known of all of them we have already mentioned previously: it is the type of cell that enables and acts as a guide for neurons during neuronal migration, allowing them to reach the positions that belong to them.

This process is especially visible during fetal development, seeing how newly formed neurons travel through glial cells, using them as a guide to the cortex. Although it is not the only neuronal migration method available, it is the best known and most widely used, especially with regard to the cerebral cortex.

In addition to this guiding and transport function, the radial glia It has also been related to the generation and neuronal synthesis itself.: It has been observed that they can act as progenitors of other cells such as neurons. This neurogenesis is especially linked to childhood, but its involvement in the birth of new cells is suspected. nerve cells in the adult brain in the few areas in which it has been detected (in the hippocampus and in the olfactory bulb is where it has been detected the most). observed). Likewise, they have been related to the recovery of some functions after the presence of brain lesions, and Its association with processes such as synaptic and neuronal pruning that occurs during the growth.

It has been seen that glial cells also have a very important role in generating a complex cerebrovascular network, functional and stable in the brain, especially in early life but also throughout the life cycle. In experiments with mice, it was observed that its inhibition generates a degradation of the cerebral vascularization network and the metabolism of the brain, something that greatly facilitates the appearance of neurodegeneration (something that in fact is discussed about its involvement in diseases such as Alzheimer's).

Finally, it is worth mentioning that, like the rest of glial cells, radial glia also have important role supporting and keeping alive the neurons that surround them, facilitating their growth and nurturing them

Bibliographic references

• Allen, N. J. and b. TO. Barres (2009). Glia – more than just brain glue. Nature, 457: 675-677.
• Malatesta, P. & Gotz, M. (2013). Radial glia: from boring cables to stem cell stars. Developments, 140: 483-486. The Company of Biologists Ltd.
• Rakick, P. (1972). Mode of cell migration to the superficial layers of fetal monkey neocortex. Journal of Compared Neurology, 145: 61-83.