CIRCADIAN REGULATION OF IODOPSIN GENE-EXPRESSION IN EMBRYONIC PHOTORECEPTORS IN RETINAL CELL-CULTURE

A circadian clock regulates number of diverse physiological functions in the vertebrate eye. In this study, we show that mRNA for the red-se nsitive cone pigment, iodopsin, fluctuates with a circadian rhythm in chicken retina. Transcript levels increase in the late afternoon just prior to the time of cone disc shedding. Furthermore, iodopsin mRNA le vels are regulated similarly by a circadian oscillator in primary cult ures of dispersed embryonic chick retina. Nuclear run-on experiments s how that the circadian regulation of iodopsin transcript abundance occ urs at the level of gene transcription. Our results provide a demonstr ation of clock-regulated gene expression in a vertebrate preparation m aintained in cell culture.