My research interests focus on Circadian biology, Neuroscience and Molecular biology.
Endogenous circadian clocks allow organisms to anticipate daily environmental changes and organize a wide array of biological functions, such as activity, sleep and feeding, in a daily schedule. To study the function and organization of these clocks we use Drosophila melanogaster as a model, due to a large degree of similarity between its molecular oscillator and the mammalian one. The molecular clock circuits in Drosophila melanogaster consist of two interlocked negative-feedback transcription loops, with a conserved central role for the heterodimeric transcription factor CLOCK/CYCLE (CLK/CYC) and its inhibitor PERIOD (PER). Whereas the components and circuits of the adult clock have been extensively studied, relatively little is known regarding the underlying developmental requirements for clock function in adult Drosophila. It was shown previously that CLK, CYC and PER are present in the larvae and that larvae can exhibit some circadian behaviour.
Our experiments show that adult circadian behaviour does not require either a functioning clock or the expression of per during prior development. However, inhibition of CLK/CYC activity during metamorphosis (post-pupal formation) either by depletion of CYC or over-expression of its inhibitor PER irreversibly affects clock-controlled locomotor activity (sleep-wake cycle) in adult flies. Even when developmental PER over-expression is restricted to 18 ventral lateral clock neurons (LNvs) expressing the neuropeptide PIGMENT DISPERSING FACTOR (PDF) subsequent adult circadian behaviour is disrupted. Spatial mapping of the arrhythmic behavioural phenotype of constitutive PER over-expression implicated the subset of small ventral lateral neurons (s-LNvs) in particular. In vivo luciferase reporter assays of circadian gene expression indicated that despite behavioural arrhythmicity, circadian oscillations persist in the peripheral tissue of adult flies and are less depended on developmental CLK/CYC activity. Thus, the newly discovered developmental function for CLK/CYC can be separated from its direct role in the circadian oscillator and it appears to be specific to the neural clock circuits. Immunofluorescence analysis of the circadian neurons of adult Drosophila with the PER over expression has revealed that both the rhythms in the oscillation of the circadian protein TIMELESS and its localization in the cells are affected, indicating a possible cause for the adult behavioural arrhythmicity. Currently we are pursuing the detailed mechanisms underlying the newly discovered developmental role for CLK/CYC.
Supervisor: Dr Herman Wijnen
PhD research: Developmental Requirements for Adult Clock Function
Funding: University of Southampton
Molecular and Cellular Biosciences
This project uses the fruit fly Drosophila melanogaster to investigate the developmental role of the conserved circadian clock component CLOCK/CYCLE.