Light, immediate-early genes, and circadian rhythms

Behav Genet. 1996 May;26(3):221-40. doi: 10.1007/BF02359382.


Many diverse behaviors exhibit clear circadian rhythms in their expression. In mammals, these rhythms originate from a neural circadian clock located in the suprachiasmatic nuclei (SCN). Recently, signaling pathways activated by light in the SCN have begun to be identified. A specific set of immediate-early genes is induced by light in the SCN, and their expression is correlated with the resetting of circadian behavioral rhythms. These light-regulated immediate-early genes offer multiple inroads into the biology of the SCN: first, they are functional markers for the activation of SCN neurons by light; second, they can direct us to the upstream light-activated (and clock-regulated) signal transduction pathways which mediate their induction; and finally, they encode transcription factor proteins which may play a role in the molecular mechanism of resetting the circadian clock.

Publication types

  • Review

MeSH terms

  • Animals
  • Circadian Rhythm / genetics*
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Genes, Immediate-Early / genetics*
  • Humans
  • Light*
  • Molecular Biology
  • Neurons / physiology
  • Proto-Oncogene Proteins c-fos / genetics
  • Signal Transduction / genetics
  • Suprachiasmatic Nucleus / physiology*


  • Cyclic AMP Response Element-Binding Protein
  • Proto-Oncogene Proteins c-fos