Photic induction of Period gene expression is reduced in Clock mutant mice.
The Clock mutation leads to abnormal circadian behavior and defective transcriptional activity of CLOCK, a basic helix-loop-helix (bHLH)/PAS protein. In situ hybridization was used to assess whether the Clock mutation affects the photic induction of mPer1, mPer2, and c-fos in the mouse suprachiasmatic nucleus (SCN). Exposure of wild-type mice to a 15 min light pulse at night rapidly induced expression of c-fos mRNA, with mPer1 and mPer2 mRNAs peaking later. Light exposure also increased c-fos, mPer1 and mPer2 mRNA levels in the SCN of homozygous Clock mutant mice, but the amplitude of the response to light was significantly reduced. Clock appears to play a role in circadian photoreception that is distinct from its role in the circadian oscillatory mechanism.
Shearman
L P
LP
Pediatric Service, Massachusetts General Hospital, Boston 02114, USA.
Weaver
D R
DR
D000818:Animals; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology; D015870:Gene Expression / Q000528:radiation effects*; D008027:Light; D051379:Mice; D008817:Mice, Mutant Strains / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D013493:Suprachiasmatic Nucleus / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D056926:CLOCK Proteins; C538944:Clock protein, mouse