The Logic of Circadian Organization in Drosophila

In the fruit fly Drosophila melanogaster, interlocked negative transcription/translation feedback loops provide the core of the circadian clock that generates rhythmic phenotypes. Although the current molecular model portrays the oscillator as cell autonomous, cross-talk among clock neurons is essential for robust cycling behavior. Nevertheless, the functional organization of the neuronal network remains obscure. Here we show that shortening or lengthening of the circadian period of locomotor activity can be obtained either by targeting different groups of clock cells with the same genetic manipulation or by challenging the same group of cells with activators and repressors of neuronal excitability. Based on these observations we interpret circadian rhythmicity as an emerging property of the circadian network and we propose an initial model for its architectural design. [Display omitted] •Locomotor activity rhythms in Drosophila have 24 hr periodicity•Different clock neurons promote either longer or shorter activity rhythms•Circadian period is an emerging property of a network of diverse oscillators•The logic connecting the network is beginning to emerge Our understanding of the circadian clock relies on the assumption that all rhythmic cells cycle with the same ∼24 hr rhythm that is characteristic of the organism as a whole. Dissel et al. show that the brain of Drosophila harbors a mosaic of cellular periodicities whose integration results in the ∼24 hr clock as we know it.