A research team studying sleep in a C. elegans model have discovered that glial cells play an important role in regulating the roundworm’s sleep-like states. Glial cells were originally thought to only provide structure and support to neurons, however, researchers have discovered that these specialized cells have several other important roles. This most recent study was published in Cell Reports. The study findings could improve the understanding of glial cell function in humans and their role in sleep and movement.
C.elegans normally continually search for food and don’t stop moving except during lethargus, a sleep-like state associated with molting. The roundworm has CEPsh glial cells that surround neurons and some synapses—the spaces that connect neurons. To study the function of CEPsh glia, the researchers removed these cells from a line of C. elegans. The researchers observed that the worms would suddenly stop in place for several seconds or minutes at a time, which was atypical behavior for C. elegans.
In addition, during lethargus, the CEPsh negative worms stayed asleep for a longer time than normal. Overall, the worms lacking CEPsh cells seemed to sleep much more than normal worms. The lack of these cells also seemed to impact their development through larval stages which was much slower than expected. This finding suggests that there is a link between development and the right amount of sleep.
Looking at CEPsh glia-covered neurons, the team found that the synapse between two neurons, one that is known to be involved in sleep (ALA) and another that controls movement (AVE), is inhibitory. When the sleep neuron is active, the movement neuron is inhibited. When ALA neurons were removed in CEPsh glia-deprived C. elegans, the worms’ abnormal drowsiness was no longer observed and their movement returned to normal. These findings indicate that ALA constantly inhibits AVE when CEPsh cells are not there suggesting that CEPsh glia counteract ALA neurons which allows normal movement. "When the animal needs to be moving, the glia are important in making sure that AVE isn't listening to ALA," says Shai Shaham, Rockefeller's Richard E. Salomon Family Professor.