Naureen Hameed¹, Sergio L. Crespo Flores¹, Evan Cirone¹, Chenyue Zhao¹, Annika F. Barber^1,2,*

Central pacemaker neurons use a combination of external stimuli and neuropeptide signaling to synchronize molecular oscillations leading to circadian behaviors. The clock network structure and signaling between these pacemaker neuron groups have been well described, but how these pacemakers communicate with specific brain output regions remains poorly understood. Here, we identified how “core” clock neurons in Drosophila, the ventrolateral neurons (LNvs), signal to the proto-hypothalamic region, the pars intercerebralis (PI). Previously thought to communicate with the PI only indirectly, we provide evidence to show that LNvs functionally modulate, the PI’s insulin-producing cells (IPCs) in a time-of-day-dependent manner. This functional connectivity relies on neuropeptidergic signaling of two canonical clock neuropeptides: pigment dispersing factor (PDF) and short Neuropeptide F (sNPF). Loss of either receptor alone in PI subpopulations does not alter feeding or locomotor rhythmicity. Further, we provide insight into how these two neuropeptides may be acting together via their receptors to signal to IPCs. We identify sexually dimorphic responses of IPC response to LNv stimulation, which may be partially explained by sex differences in proximity of clock neurons to the PI. Our findings indicate that LNvs form both direct peptidergic signaling but also form indirect multisynaptic circuits with IPCs, which may model more broadly how they communicate with various other clock output regions.

¹ Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA.

² Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, Piscataway, NJ, 08854, USA.

* annika.barber@waksman.rutgers.edu