Insulin signaling in clock neurons regulates sleep in Drosophila.

Sleep relates to numerous biological functions, including metabolism. Both dietary conditions and genes related to metabolism are known to affect sleep behavior. Insulin signaling is well conserved across species including the fruit fly and relates to both metabolism and sleep. However, the neural mechanism of sleep regulation by insulin signaling is poorly understood. Here, we report that insulin signaling in specific neurons regulates sleep in Drosophila melanogaster. We analyzed the sleep behavior of flies with the mutation in insulin-like ligands expressed in the brain and found that three insulin-like ligands participate in sleep regulation with some redundancy. We next used 21 Gal4 drivers to express a dominant-negative form of the insulin receptor (InR DN) in various neurons including circadian clock neurons, which express the clock gene, and the pars intercerebralis (PI). Inhibition of insulin signaling in the anterior dorsal neuron group 1 (DN1a) decreased sleep. Additionally, the same manipulation in PI also decreased sleep. Pan-neuronal induced expression of InR DN also decreased sleep. These results suggested that insulin signaling in DN1a and PI regulates sleep.