Diurnal rhythmic expression of the rhythm-related genes, rPeriod1, rPeriod2, and rClock, in the rat brain.
High densities of the mRNA of three rhythm-related genes, rPeriod1 (rPer1), rPer2, and rClock, which share high homology in Drosophila and mammals, are found in the rat hypothalamic suprachiasmatic nucleus (SCN). The SCN, however, is not the only brain region that expresses these genes. To understand the possible physiological roles of these rhythm-related genes, we examined expression of these genes in different brain regions at various time points in male Sprague--Dawley rats. Using semi quantitativein situ hybridization with 35S-riboprobes to evaluate mRNA levels, the diurnal rhythmicity of rPer1, and rPer2 mRNA levels was found in the SCN, arcuate nucleus, and median eminence/pars tuberalis. Expression patterns of mRNA for rPer1 and rPer2, however, were not similar in these brain regions. The rhythmicity in these brain regions was specific, because it was not observed in the cerebellum or hippocampus. Moreover, diurnal changes in rClock mRNA expression were not detected in any of the brain regions examined. These findings suggest that the different expression patterns observed for rPer1, rPer2, and rClock mRNAs may be attributed to their different physiological roles in these brain regions, and support previous work indicating that circadian rhythms in the brain are widespread.
Shieh
Kun-Ruey
KR
Institute of Neuroscience, Tzu Chi University, Hualien 970, ROC. krishieh@mail.tcu.edu.tw
Yang
Shu-Chuan
SC
Lu
Xin-Yun
XY
Akil
Huda
H
Watson
Stanley J
SJ
D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D056926:CLOCK Proteins; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D017403:In Situ Hybridization; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539023:Per1 protein, mouse; C539024:Per1 protein, rat; C513312:Per2 protein, mouse; C513311:Per2 protein, rat; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D056926:CLOCK Proteins; C538944:Clock protein, mouse; C538945:Clock protein, rat