Modelling of Circadian Rhythms

Circadian rhythms (from latin circa, about; and dies, day) play important roles in the adaptation of organisms to their natural environment. It is assumed that by measuring day length, the circadian clock participates in the initiation of important daily processes, for example sleep or activity rhythms as well as in the induction of seasonal processes such as flower induction, migration of birds and certain butterflies, or hibernation. In order to work as physiological clocks, circadian rhythms have homeo static compensation mechanisms such as temperature compensation, meaning that the period is practically kept constant at different environmental conditions (for example temperature). An important aspect in trying to understand these regulatory mechanisms and the properties of circadian rhythms is their description by (mathematical) reaction kinetic models. In such an approach the component physiological processes are described as coupled first-order differential equations which are solved numerically. In this project we are developing mathematical tools and reaction kinetic models to describe properties of circadian rhythms. Special attention is given to temperature compensation and the effective calculation of control coefficients Ci. The control coeffic ients describe how sensitive the period of the rhythm is upon variation of the rate constants (and environmental parameters such as temperature) indexed by ?i?. They are important because they provide constraints for temperature compensation to occur in a reaction kinetic model. The specific goal of this project is to provide for experimentalists a comprehensive model of the circadian clock (for the model organism Neurospora crassa), which can be tested in the laboratory.