Astrocytes Set the Pace of Our Body Clocks
The suprachiasmatic nucleus of the hypothalamus is the master clock of the body. This small nucleus at the base of the brain orchestrates the daily behavioral and physiological rhythms of the human body that wake us up in the morning and put us to sleep at night. Until now, it was thought that these 24-hour sleep/wake oscillations were caused by the periodical changes in gene expression and electrical activity within the neurons of this clock nucleus as disrupting the activity of the clock neurons affects the sleep-wake cycles of experimental animals.
In their article published recently, which features on the front cover of Neuron, the Hastings Group describe their findings that astrocytes control sleep/wake cycles. Lead author, Dr Marco Brancaccio explains, “When we re-programmed the periodic gene expression changes in astrocytes in the suprachiasmatic nucleus, we were surprised to find that sleep/wake behavior was also re-programmed.”
The team looked deeper into the mechanisms underlying their finding. Using organotypic culture methods, the team made explants of the clock nucleus from mice that express fluorescent proteins and reporter molecules in their brain cells. This special form of culture keeps the tissue alive and healthy for several days up to weeks, enabling long-term measurements of cellular activity.
Immunofluorescence image of the Suprachiasmatic Nucleus (SCN, labelled blue). Astrocytes are shown in green and Neurons of the dorsal SCN in magenta. Hastings Group MRC LMB.
The team wanted to understand the mechanistic basis for this reciprocal activity at the level of the receptors expressed in the cell membranes.
This comprehensive investigation of body clock control by astrocytes from the level of the receptor up to the freely behaving animal underlies the importance of these cells in maintaining normal physiology.
Reference:Brancaccio, M., Patton, A., Chesham, J., Maywood, E. and Hastings, M. (2017). Astrocytes Control Circadian Timekeeping in the Suprachiasmatic Nucleus via Glutamatergic Signaling. Neuron. http://dx.doi.org/10.1016/j.neuron.2017.02.030Adapted from original article by Dr Adam Tozer (Technology Networks)
Posted on 04/04/2017
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