Molecular and cellular dissection of morning and evening chronotypes in drosophila melanogaster

For many of us life is mainly spent indoors, so we are no longer exposed to the natural variations in light and temperature that characterise the day-night cycle. . Moreover, the rhythm of life is such that for many people the economic or social call to start a new day comes hours before the endogenous call from the body clock. The combined effect of these two lifestyles causes a discrepancy between internal and external timing which, can be more or less pronounced for late rising 'owl' or early rising 'lark' chronotypes. This creates a clock dysfunction that is not only reflected in temporal disorientation and sleep problems, but also in pathologies such as obesity, mental illness, cardiovascular disease and cancer. To improve the quality of life, new policies and interventions that consider the issue of TIME are urgently required. However, to translate the insights of circadian biology into real life, a comprehensive understanding of how the circadian clock works is a prerequisite. The fruitfly Drosophila melanogaster is an ideal model organism for the study of circadian rhythms because the clock mechanism shares the same design and molecular components with mammals. Our collaborator, Dr Sharma (Bangalore), applied artificial selection to create flies that are 'owls' or 'larks' in their timing of emergence from the pupa a character that is under circadian control. These populations offer a unique opportunity to study how these 'chronotypes' come to exist, because they can be analysed at the molecular and cellular levels to identify their underlying genetic and anatomical substrates. By taking a large scale approach embracing the whole system (systems biology) we will be able to ascertain whether the main differences between 'owls' and 'larks' reside in the genes that control the core of the clock in the brain, or in those that are involved in its rhythmic output via peripheral organs, or both. Our work will contribute to a fuller comprehension of the biology of the circadian clock, and provide a novel framework for understanding human chronotypes. In addition, by focusing on emergence, a key process in the insect life-cycle, it will have implications within applied entomology for future medical, industrial and agricultural interventions.

It has become apparent in recent years that the human circadian system shows natural variation in terms of the chronotypes that are expressed (eg 'larks' versus 'owls'). Given the underlying conservation of the fly and human circadian mechanism at the molecular level, fly chronotypes represent a potentially powerful model system to study such variation. Our collaborator in India, has generated selected fly lines that show early day and late day circadian eclosion, which have a significant phase difference in adult emergence, but only a small difference in circadian period. We plan to study these 'chronotypes' by subjecting them to a modified QTL analysis in order to identify their underlying genetic bases. We shall complement this genomic analysis with global expression profiling using an Affymetrix platform. It is hoped that these two approaches may identify all the differences between early and late flies irrespective of whether they originate from changes in the coding or in the regulatory regions of genes. Any candidate genes identified from the genomic and/or expression studies will be subsequently disrupted with the use of mutants or RNAi, to validate their contributions to the chronotype. We shall also generate a number of novel constructs using GAL4/UAS and FLP/FRT , to dissect out the anatomical substrates that underlie the two phenotypes, and to assess the importance of central versus peripheral clocks in generating these phase differences in behaviour. We suspect that our results will provide a novel theoretical framework by which to understand the origins of human chronotypes.

Our study of fly chronotypes and their underlying genetic, molecular and anatomical substrates will provide a novel perspective and theoretical framework by which to study human chronotypes. Given the current public concern about the chronically 'jet-lagged' human population, our work may have some direct implications for remedial action in terms of adapting chronotypes to their optimal temporal environments. The similarities between flies and mammals in the genetic basis of their circadian system, also means that any new genes that we identify that underlie fly chronotypes, may have interesting mammalian homologues (or analogues), with similar functions. While the research is 'pure', there are further downstream implications for our research, even if these are not immediate. Other beneficiaries apart from the academic beneficiaries would thus be 1. The medical profession. 2. The pharmaceutical industry who might be interested in our genes as potential targets. 3. Agricultural and medical entomologists interested in controlling problem insects using eclosion as a target. 4. Policymakers who are concerned about the effects of our 'round the clock' lifestyles, and the additional burden this puts on the health services. 5. The public, who is always very curious and responsive to issues concerning the body clock. As with all basic research, it could be many years down the line before any of the discoveries we will make might be translated into drugs, treatments and policies. However, the work of many chronobiologists (including ourselves) has produced, through the years, a tangible effect on the culture and the knowledge of the UK (and the Western world). Nowadays everybody is aware of the existence of a body clock and of its tremendous power in regulating our lives. We have many years of experience in talking to schoolchildren and their teachers, to the general public in open lectures, to artists and to the press. We also communicate with the medical profession and with applied researches in the form of publications, and by dissemination at conferences. We will update our websites, open to anyone, so that any informed citizen will have the opportunity to understand the problems we are concerned with in our research and to echo them to policy makers. Furthermore, we are open to collaborations with any interested groups, academic, or commercial. Our project will also contribute to the cultural and economic growth of the UK by enhancing the skills of the staff that will be working on the proposed research. Staff will gain specialised skills through performing advanced laboratory techniques and data analysis. These are generally and widely applicable to their subsequent career progression in molecular biology. In addition, transferable skills that will be acquired in the form of public speaking, computing and writing are again widely relevant to any professional forum. Finally, we will contribute to the success of the UK through high quality publications in top scientific journals. This is an essential metric for the evaluation of the international prestige of a nation with political and economic repercussions.