Snapshot: What are Astrocytes?

The human brain contains about 170 billion cells. Half of these are neurons and the other half are lesser known cells called glia. Glial cells include astrocytes, oligodendrocytes and microglia. Astrocytes tile the entire brain and interact closely with neurons. Astrocytes are very important for neuronal function, in many ways playing a parenting-like role. They provide energy and support to neurons, and they clean after them. Astrocytes make sure that neuronal surroundings are “just right” for optimal function of neurons. They can also actively influence neuronal activity.

An astrocyte cell grown in tissue culture stained with antibodies to GFAP and vimentin. The GFAP is coupled to a red fluorescent dye and the vimentin is coupled to a green fluorescent dye. Both proteins are present in large amounts in the intermediate filaments of this cell, so the cell appears yellow, the result of combining strong red and green signals. The blue signal is DNA revealed with DAPI, and shows the nucleus of the astrocyte and of other cells in this image.
An astrocyte cell imaged using a microscope and colored antibodies. Imaged courtesy of Wikimedia.

Similar to neurons, there are important differences in astrocytes from different brain regions. For instance, in the cerebellum there are about 5 times more neurons than astrocytes. Meanwhile in the cortex there are 10 times more astrocytes than neurons. In addition, astrocytes in the cerebellum and hippocampus (a brain region that plays an important role in memory) express different sets of proteins. These brain region differences can contribute to the role that astrocytes play in neuronal function in health as well as in disease.

Bergman Glia: An Important type of Astrocyte in Ataxia

In the cerebellum, there is a special type of astrocyte called Bergman glia that are very closely connected with Purkinje cells, neurons that are often vulnerable in ataxia. In fact, the relationship between Purkinje cells and Bergmann glia is often referred to as the most intimate neuron-astrocyte relationship in the brain. This is important as in brain injury and neurodegenerative diseases astrocytes undergo process called gliosis that changes their function. Gliosis can make them either more neuroprotective (helpful) or harmful.

For instance, when there is disease Bergmann glia can increase their support to help Purkinje neurons maintain their function and delay onset of disease symptoms. But also, Bergmann glia can become harmful worsening the dysfunction of Purkinje neurons and more severe disease symptoms.

Bergmann glia  help support Purkinje cells early on in ataxia, but as the disease progresses they can actual make symptoms worse.
Illustrating intimate relationship between Bergmann glia (BG) and Purkinje cells (PC). Bergmann glia may increase their support to Purkinje cells early in disease. However, they can become harmful with disease progression. Image desgined by Marija Cvetanovic.

It is important to learn more about how astrocytes are altered in ataxia for these reasons. We can use that knowledge about astrocytes to develop novel therapies to delay onset of ataxia symptoms and their severity.

If you would like to learn more about astrocytes, take a look at these resources by Khan Academy and Tempo Bioscience.

Snapshot written by Dr. Marija Cvetanovic and edited by David Bushart.