Temporal and spatial expression patterns of canonical clock genes and clock-controlled genes in the suprachiasmatic nucleus.
In mammals, the suprachiasmatic nuclei (SCN) of the hypothalamus control endogenous circadian rhythms and entrainment to the environment. A core SCN region of calbindin (CalB)-containing cells is retinorecipient and the cells therein lack rhythmic expression of clock genes and electrical activity. The core is surrounded by a 'shell' of rhythmic oscillator cells. In the present experiments, we studied the spatial arrangement of oscillator cells by examining the spatial and temporal patterns of expression of the canonical clock genes Per1, Per2 and vasopressin mRNA, a clock-controlled gene. Surprisingly, in the SCN shell, the dorsomedial cells were the first to rhythmically express both Per1 and VP mRNA, with gene expression then spreading very slowly through much of the nucleus for the next 12 h then receding to baseline levels. Following a light pulse, Per expression increased after 1 h in the core SCN and after 1.5 h in the shell. Although expression in the shell occurred earlier in light-pulsed animals than in those housed in constant darkness, it still followed the same spatial and temporal expression pattern as was observed in constant darkness. The results suggest that not only is the SCN organized into light-responsive and rhythmic regions but also that the rhythmic region of the SCN itself has an ordered arrangement of SCN oscillator cells.
Hamada
Toshiyuki
T
Department of Psychology, Columbia University, 1190 Amsterdam Avenue, New York, NY 10027, USA.
Antle
Michael C
MC
Silver
Rae
R
D000818:Animals; D064026:Calbindins; D002452:Cell Count / Q000379:methods; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000235:genetics*; D006224:Cricetinae; D004076:Digoxigenin / Q000378:metabolism; D005786:Gene Expression Regulation / Q000528:radiation effects; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D010775:Photic Stimulation; D017440:Photoperiod; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors; D014157:Transcription Factors; D014667:Vasopressins / Q000235:genetics / Q000378:metabolism*
D064026:Calbindins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D014157:Transcription Factors; D014667:Vasopressins; D004076:Digoxigenin