A recent study suggests that astrocytes (a type of star-shaped glial cells) may ultimately play a much bigger role than previously thought in our bodies by regulating our circadian rhythm.
An astrocyte is a glial cell of the central nervous system. We knew that they play important functional roles by participating in particular in gliosis, the phenomenon of scarring of lesions of the nervous system. They also intervene at the level of the synapses to capture the neurotransmitters or at the level of the capillaries to ensure the blood-brain barrier. They also have a role in transporting molecules and supplying neurons with lactate. In contrast, we thought astrocytes only had a supporting and structural role in the central nervous system, but a recent study by researchers at Washington University in St Louis suggests that astrocytes ultimately play a role major role in regulating our circadian rhythm.
Until recently, research on biological clocks has focused only on neurons. Our internal clock has long been thought to be controlled by the suprachiasmatic nuclei (SCN), a region of the brain in the hypothalamus made up of approximately 20,000 neurons. But we also know that nearly 6,000 astrocyte cells also sit in the same area, although their exact function has never been fully understood. Considered « secondary », they would in fact be more important than we thought. By isolating astrocytes from the neurons with which they were intertwined, researchers have now been able to alter astrocyte clocks in mice and then monitor their behavior. And what was their surprise!
By fluorescence, the scientists were able to observe that astrocytes express the clock gene according to a rhythmic pattern: in other words, astrocytes keep track of time in living tissues where they interact with each other and with neurons. Finally, when the scientists deleted the clock gene in astrocytes via the new gene-editing tool CRISPR-Cas9, they then realized that the mice’s internal clock had slowed down and shifted by about an hour a day.
Scientists still don’t know how astrocytes interact with neurons in this timing function. Of course, we cannot yet guarantee that astrocytes also regulate body clocks in the same way in humans. Future studies should soon give us the answer.
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