Circadian rhythm and light regulate opsin mRNA in rod photoreceptors.
Disk membranes in the outer segment of rod photoreceptors are continuously renewed, being assembled at the outer segment base, displaced outward by new disks and eventually shed at the tip. In lower vertebrates, disk assembly occurs with a diurnal rhythm with 2-4% of the outer segment length produced daily. We have discovered that in toad and fish retinas the level of mRNA for opsin, the most abundant protein in rod disks, fluctuates with a daily rhythm and is regulated both by light and by a circadian oscillator. The mRNA level rises before light onset, remains high during the light phase of a diurnal cycle and decreases four to tenfold during the dark phase. In constant darkness, mRNA elevation occurs during subjective daytime. At night, rod opsin mRNA can be elevated by exposure to light.
Korenbrot
J I
JI
Department of Physiology, School of Medicine, University of California, San Francisco 94143.
Fernald
R D
RD
D000818:Animals; D002024:Bufo marinus / Q000378:metabolism*; D002940:Circadian Rhythm; D005136:Eye Proteins / Q000235:genetics*; D005399:Fishes / Q000378:metabolism*; D008027:Light; D009693:Nucleic Acid Hybridization; D010507:Periodicity; D010786:Photoreceptor Cells / Q000378:metabolism* / Q000528:radiation effects; D015347:RNA Probes; D012333:RNA, Messenger / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D017299:Rod Opsins
D005136:Eye Proteins; D015347:RNA Probes; D012333:RNA, Messenger; D017299:Rod Opsins