A Component of Retinal Light Adaptation Mediated by the Thyroid Hormone Cascade

Neurobiology Sector, International School for Advanced Studies (SISSA), Trieste, Italy.
PLoS ONE (Impact Factor: 3.23). 10/2011; 6(10):e26334. DOI: 10.1371/journal.pone.0026334
Source: PubMed


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.

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Available from: Diana Bedolla
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    • "Serial, coronal sections (40 ␮m) of the hypothalamus of each CCI and BC rat (all identified PD rats and randomly chosen ND and BC rats) were cut on a cryostat (Leica), and collected in a one in five series into 0.1 M PBS (pH 7.4); one series was Nissl stained for anatomical validation of the remaining immunohistochemically stained series. The remaining series were incubated as free-floating sections in one of the following antibodies: rabbit polyclonal antibody to Thyroid Hormone Receptor ␤ (TR␤) (ab5622, abcam ® ); this antibody has been used in human heart muscle and rat liver (Sun et al., 2007; Liu et al., 2007; Modesti et al., 2008): goat polyclonal antibody to Deiodinase 2 enzyme (Dio2) (ab77481, abcam ® ); this product has been used to identify Dio2 in mouse heart muscle and characterised using Western blot (Wang et al., 2010): rabbit polyclonal antibody to Deiodinase 3 enzyme (Dio3) (ab82041, abcam ® ); this product has been used to identify Dio3 in rat retina and characterised using Western blot (Bedolla and Torre, 2011). "
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