title: A component of retinal light adaptation mediated by the thyroid hormone cascade.
abstract: Analysis with DNA-microrrays and real time PCR show that several genes involved in the thyroid hormone cascade, such as deiodinase 2 and 3 (Dio2 and Dio3) are differentially regulated by the circadian clock and by changes of the ambient light. The expression level of Dio2 in adult rats (2-3 months of age) kept continuously in darkness is modulated by the circadian clock and is up-regulated by 2 fold at midday. When the diurnal ambient light was on, the expression level of Dio2 increased by 4-8 fold and a consequent increase of the related protein was detected around the nuclei of retinal photoreceptors and of neurons in inner and outer nuclear layers. The expression level of Dio3 had a different temporal pattern and was down-regulated by diurnal light. Our results suggest that DIO2 and DIO3 have a role not only in the developing retina but also in the adult retina and are powerfully regulated by light. As the thyroid hormone is a ligand-inducible transcription factor controlling the expression of several target genes, the transcriptional activation of Dio2 could be a novel genomic component of light adaptation.
authors: Neurobiology Sector, International School for Advanced Studies (SISSA), Trieste, Italy.
authors: Diana E
authors: DE
authors: Bedolla
authors: Vincent
authors: V
authors: Torre
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001483:Base Sequence; D002940:Circadian Rhythm; D017931:DNA Primers; D003624:Darkness; D007150:Immunohistochemistry; D007453:Iodide Peroxidase / Q000235:genetics / Q000378:metabolism; D008027:Light; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D012160:Retina / Q000201:enzymology / Q000502:physiology*; D013963:Thyroid Hormones / Q000502:physiology*
chemical_list: D017931:DNA Primers; D013963:Thyroid Hormones; D007453:Iodide Peroxidase