Cells Once Thought Only To Be Scaffolding May Be Keeping Time In Our Brains

The researchers tagged the proteins responsible for keeping time with a green flourescent protein. Washington University in St. Louis

Josh Davis 27 Mar 2017, 20:40

One's internal clock is crucial for the maintenance of a working body. From body temperature to brain waves, many of our functions are driven by this circadian rhythm, which is primarily controlled by a part of the brain known as the suprachiasmatic nucleus (SCN).

This tiny region of the brain is composed of several types of cells, including those known as astrocytes. Until recently, it was thought that astrocytes simply functioned like glue, or scaffolding, in the SCN for the neurons, which did the real job of keeping time. But it now seems that the astrocytes may in fact be the ones pulling the strings, setting the pace for the SCN as it ticks away.

The body’s biological clock works, in effect, like an hourglass. Cells produce a particular protein that, when it reaches a certain level, induces the cell to shut down production of the protein, before a feedback loop basically flips the hourglass and the clock carries on ticking. The genes that make up this biological clock were initially thought to be found only in the neurons of the SCN, until they were found littered throughout the body in almost every cell.

The astrocyte cells in the SCN expressing their clock genes to keep time. Herzog lab

Back in 2005, Erik Herzog, a neuroscientist at Washington University, discovered that the astrocytes in the SCN were able to keep time. However, it was almost impossible to study them independently because the astrocytes were supporting the neurons. It has only been recently that researchers have been able to decode the exact role that the astrocytes play. 

Matt Tso, a graduate student of Herzog’s, managed to come up with a way in which the astrocytes in the SCN could be altered separately of the neurons. This means that the researchers could now test the astrocytes to see what they do. As it turned out, fiddling with these cells in mice slowed down their sense of time. “We had no idea they would be that influential,” says Tso, lead author of the paper now published in Current Biology, in a statement.

They were even able to grow the astrocytes on their own in a petri dish and added a bioluminescent protein to the clock gene in the cells. By doing this, the researchers were able to watch as the cells slowly lit up and then dimmed in a rhythmic fashion as the cells' clock kept time.

By doing a similar thing while the astrocytes were still entwined with the SCN neurons, coupled with the knockouts they performed on the mice, they were able to confirm the importance of the cells in keeping time.

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