Temperature Dependence in Drosophila Circadian Circuit

The circadian clock, the endogenous clock present in almost all life forms, allows organisms to maximize their survival by aligning various biological processes to the day-night cycle caused by the earth’s rotation. The clock regulates a multitude of behavioural and molecular pathways including reproduction, metabolism and hormone secretion. Greater knowledge of the circadian clock would potentially help us understand the health risks associated with disrupted daily rhythms in the modern world. Although the basic molecular mechanisms underlying the cell-autonomous clock have been extensively studied, the neuronal interactions that produces behavioral rhythms remain poorly understood.

This thesis investigates the relative contributions of different clock neurons to behavioural rhythmicity of Drosophila melanogaster, as a function of ambient temperature. To study the role of specific clock neurons in rendering different aspects of rhythmicity, various perturbations were introduced in the circadian network and locomotor activity rhythms were monitored at two different temperatures. Methods of perturbing the circadian network included cell-specific neuronal ablation, neuron-specific rescue of functional clock in an otherwise arrhythmic background, and CRISPR/Cas9 knockout of clock genes in specific neurons. The results of these experiments reveal temperature-dependent changes in the circadian outputs of different clock neuron groups and reinforces the importance of neuronal communication in the emergence of behavioural rhythms.