Polyphasic circadian neural circuits drive differential activities in multiple downstream rhythmic centers.

Area of Science:

• Neuroscience
• Chronobiology
• Genetics

Background:

• Circadian clocks regulate daily behaviors for optimal adaptation.
• The translation of pacemaker circuit rhythms to neuronal outputs remains unclear.

Purpose of the Study:

• Investigate circadian rhythmic activity in Drosophila dopaminergic and neurosecretory neurons.
• Determine how pacemaker network activity drives downstream neuronal outputs.

Main Methods:

• Utilized brain-wide, 24-hour in vivo calcium imaging in Drosophila.
• Identified and analyzed circadian rhythmic activity in specific neuron clusters.

Main Results:

• Discovered widespread circadian rhythms in dopaminergic (DA) and neurosecretory (NS) neurons, driven by the PERIOD-dependent pacemaker network.
• Identified distinct morning (M), evening (E), and mid-day (MD) pacemaker phases.
• Demonstrated that different pacemaker subgroups regulate specific downstream neurons, including DA-PPM3, DA-PAL, DA-PPL1, DA-PPM1/2, and three NS cell types.

Conclusions:

• The Drosophila circadian pacemaker network functions as a polyphasic rhythm generator with dedicated M, E, and MD phases.
• These phases are functionally transduced into neuronal outputs to organize diverse daily activity patterns in downstream circuits.