The Development and Decay of the Circadian Clock in .

The way in which the circadian clock mechanism develops and decays throughout life is interesting for a number of reasons and may give us insight into the process of aging itself. The model has been proven invaluable for the study of the circadian clock and development and aging. Here we review the evidence for how the clock develops and changes throughout life, and present a new conceptual model based on the results of our recent work. Firefly luciferase lines faithfully report the output of known clock genes at the central clock level in the brain and peripherally throughout the whole body. Our results show that the clock is functioning in embryogenesis far earlier than previously thought. This central clock in the fly remains robust throughout the life of the animal and only degrades immediately prior to death. However, at the peripheral (non-central oscillator level) the clock shows weakened output as the animal ages, suggesting the possibility of the breakdown in the cohesion of the circadian network.