Pigment-dispersing factor and CCHamide1 in the Drosophila circadian clock network

ABSTRACT

Animals possess a circadian central clock in the brain, where circadian behavioural rhythms are generated. In the fruit fly (Drosophila melanogaster), the central clock comprises a network of approximately 150 clock neurons, which is important for the maintenance of a coherent and robust rhythm. Several neuropeptides involved in the network have been identified, including Pigment-dispersing factor (PDF) and CCHamide1 (CCHa1) neuropeptides. PDF signals bidirectionally to CCHa1-positive clock neurons; thus, the clock neuron groups expressing PDF and CCHa1 interact reciprocally. However, the role of these interactions in molecular and behavioural rhythms remains elusive. In this study, we generated Pdf ⁰¹ and CCHa1^SK8 double mutants and examined their locomotor activity-related rhythms. The single mutants of Pdf ⁰¹ or CCHa1^SK8 displayed free-running rhythms under constant dark conditions, whereas approximately 98% of the double mutants were arrhythmic. In light-dark conditions, the evening activity of the double mutants was phase-advanced compared with that of the single mutants. In contrast, both the single and double mutants had diminished morning activity. These results suggest that the effects of the double mutation varied in behavioural parameters. The double and triple mutants of per ⁰¹, Pdf ⁰¹, and CCHa1^SK8 further revealed that PDF signalling plays a role in the suppression of activity during the daytime under a clock-less background. Our results provide insights into the interactions between PDF and CCHa1 signalling and their roles in activity rhythms.

KEYWORDS:

• Neuropeptide
• neural network
• clock protein
• activity rhythm
• masking effect

Acknowledgements

We would like to thank C. J. P. Grimmelikhuijzen, P. H. Taghert, J. Giebultwicz, K. Tomioka, the Developmental Studies Hybridoma Bank, and the Bloomington Drosophila Stock Center for providing us with materials and reagents. We also thank the Division of Instrumental Analysis, Okayama University for letting us use a laser scanning confocal microscope (FV1200).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the JSPS (KAKENHI 19H03265).