Circadian clocks--from genes to complex behaviour.
Circadian clocks control temporal structure in practically all organisms and on all levels of biology, from gene expression to complex behaviour and cognition. Over the last decades, research has begun to unravel the physiological and, more recently, molecular mechanisms that underlie this endogenous temporal programme. The generation of circadian rhythms can be explained, at the molecular level, by a model based upon a set of genes and their products which form an autoregulating negative feedback loop. The elements contributing to this transcriptional feedback appear to be conserved from insects to mammals. Here, we summarize the process of the genetic and molecular research that led to 'closing the molecular loop'. Now that the reductionist approach has led to the description of a detailed clock model at the molecular level, further insights into the circadian system can be provided by combining the extensive knowledge gained from decades of physiological research with molecular tools, thereby reconstructing the clock within the organism and its environment. We describe experiments combining old and new tools and show that they constitute a powerful approach to understanding the mechanisms that lead to temporal structure in complex behaviour.
Roenneberg
T
T
Institute for Medical Psychology, Ludwig Maximilians University, Munich, Germany. till.roenneberg@imp.med.uni-muenchen.de
Merrow
M
M
D056930:ARNTL Transcription Factors; D000828:Animal Population Groups / Q000235:genetics / Q000502:physiology; D000818:Animals; D018407:Bacterial Physiological Phenomena; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology; D005246:Feedback; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D017343:Genes, Plant; D019476:Insect Proteins / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics; D056950:Period Circadian Proteins; D017440:Photoperiod; D010944:Plants / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D029721:Drosophila Proteins; D005656:Fungal Proteins; D019476:Insect Proteins; D009687:Nuclear Proteins; D056950:Period Circadian Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C087405:FRQ protein, Neurospora crassa; C539040:PER protein, Drosophila