title: Theoretical models for circadian rhythms in Neurospora and Drosophila.
abstract: We examine theoretical models proposed for the molecular mechanism of circadian rhythms in Drosophila. The models are based on the negative feedback exerted by a complex between the PER and TIM proteins on the expression of the per and tim genes. We show that a similar model can account for circadian oscillations in Neurospora, where the protein FRQ negatively regulates the expression of the frq gene. The effect of light on the circadian rhythms is included by considering that it elicits a rise in the rate of TIM degradation in Drosophila, whereas in Neurospora it enhances the rate of frq transcription. The models account for the occurrence of sustained circadian oscillations in continuous darkness in Drosophila and Neurospora. Numerical simulations further indicate that the periodic forcing of circadian oscillations by light-dark cycles can result either in the entrainment to the external periodicity or in aperiodic oscillations (i.e. chaos), depending on the magnitude of the periodic changes in the light-controlled parameter.
authors.affiliation: Faculté des sciences, université libre de Bruxelles, Belgium.
authors.forename: D
authors.initials: D
authors.lastname: Gonze
authors.forename: J C
authors.initials: JC
authors.lastname: Leloup
authors.forename: A
authors.initials: A
authors.lastname: Goldbeter
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins; D005246:Feedback; D005656:Fungal Proteins / Q000235:genetics; D015870:Gene Expression; D019476:Insect Proteins / Q000235:genetics; D008433:Mathematics; D008954:Models, Biological; D009491:Neurospora / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics; D056950:Period Circadian Proteins
chemical_list: D029721:Drosophila Proteins; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; C096445:tim protein, Drosophila