Analysis of clock proteins in mouse SCN demonstrates phylogenetic divergence of the circadian clockwork and resetting mechanisms

Neuron. 2000 Feb;25(2):437-47. doi: 10.1016/s0896-6273(00)80906-x.


The circadian clock in the suprachiasmatic nuclei (SCN) is comprised of a cell-autonomous, autoregulatory transcriptional/translational feedback loop. Its molecular components include three period and two cryptochrome genes. We describe circadian patterns of expression of mPER2 and mPER3 in the mouse SCN that are synchronous to those for mPER1, mCRY1, and mCRY2. Coimmunoprecipitation experiments demonstrate in vivo associations of the SCN mPER proteins with each other and with the mCRY proteins, and of mCRY proteins with mTIM, but no mPER/mTIM interactions. Examination of the effects of weak and strong resetting light pulses on SCN clock proteins highlights a central role for mPER1 in photic entrainment, with no acute light effects on either the mCRY or mTIM proteins. These clock protein interactions and photic responses in mice are divergent from those described in Drosophila.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Cycle Proteins
  • Circadian Rhythm / genetics*
  • Cryptochromes
  • Drosophila
  • Drosophila Proteins*
  • Eye Proteins*
  • Flavoproteins / analysis
  • Flavoproteins / genetics
  • Gene Expression / physiology
  • Genetic Variation
  • In Situ Hybridization
  • Male
  • Mice
  • Mice, Inbred Strains
  • Nuclear Proteins / analysis
  • Nuclear Proteins / genetics*
  • Period Circadian Proteins
  • Photic Stimulation
  • Photoreceptor Cells, Invertebrate*
  • Phylogeny*
  • RNA, Messenger / analysis
  • Receptors, G-Protein-Coupled
  • Suprachiasmatic Nucleus / chemistry
  • Suprachiasmatic Nucleus / physiology
  • Transcription Factors


  • Cell Cycle Proteins
  • Cryptochromes
  • Drosophila Proteins
  • Eye Proteins
  • Flavoproteins
  • Nuclear Proteins
  • Per2 protein, mouse
  • Per3 protein, mouse
  • Period Circadian Proteins
  • RNA, Messenger
  • Receptors, G-Protein-Coupled
  • Transcription Factors
  • cry protein, Drosophila