The Drosophila Circadian Clock Is a Variably Coupled Network of Multiple Peptidergic Units

Circadian Rhythms Circadian rhythms in the fruit fly Drosophila are driven by neurons in the brain. Yao and Shafer (p. 1516) analyzed different sets of neurons that can drive circadian rhythms. Manipulating the period of each set of neurons separately revealed that when the various clock signals were fairly consistent, the fly showed a robust circadian rhythm. But when the various clock signals were seriously out of sync with one another, the fly was oblivious to the day-night cycle. Behavioral rhythms emerge from the interactions of many independent oscillators rather than from a group of master pacemakers. Daily rhythms in behavior emerge from networks of neurons that express molecular clocks. Drosophila’s clock neuron network consists of a diversity of cell types, yet is modeled as two hierarchically organized groups, one of which serves as a master pacemaker. Here, we establish that the fly’s clock neuron network consists of multiple units of independent neuronal oscillators, each unified by its neuropeptide transmitter and mode of coupling to other units. Our work reveals that the circadian clock neuron network is not orchestrated by a small group of master pacemakers but rather consists of multiple independent oscillators, each of which drives rhythms in activity.

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