Time after time: inputs to and outputs from the mammalian circadian oscillators.
Oscillating levels of clock gene transcripts in the suprachiasmatic nucleus (SCN) are essential components of the mammalian circadian pacemaker. Their synchronization with daily light cycles involves neural connections from light-sensitive photoreceptor-containing retinal ganglion cells. This clock orchestrates rhythmic expression for approximately 10% of the SCN gene transcripts, of which only 10% are also rhythmically expressed in other tissues. Many of the transcripts expressed rhythmically only in the SCN are involved in neurosecretion, and their secreted products could mediate SCN control over physiological rhythms by coordinating rhythmicity in other nuclei within the brain. The coordination of clock gene transcript oscillations in peripheral tissues could be controlled directly by specific signals or indirectly by rhythmic behavior such as feeding.
Morse
David
D
Dept des Sciences Biologiques, Université de Montréal, 4101 Sherbrooke est, Montréal Quebec, Canada H1X 2B2.
Sassone-Corsi
Paolo
P
D000818:Animals; D001683:Biological Clocks / Q000235:genetics* / Q000502:physiology; D002940:Circadian Rhythm / Q000235:genetics*; D025461:Feedback, Physiological / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000502:physiology*