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Cryptochromes mediate rhythmic repression of the glucocorticoid receptor

ABSTRACT: The circadian transcriptional repressors cryptochromes 1 (Cry1) and 2 (Cry2) interact with the C-terminus of the glucocorticoid receptor (GR) and are required for transrepression in response to the synthetic GR ligand dexamethasone (Dex) in mouse embryonic fibroblasts. Dex induction of many genes was increased in Cry-deficient fibroblasts suggesting that cryptochromes oppose transactivation in addition to contributing to transrepression. In mice, genetic loss of Cry1 and/or Cry2 resulted in glucose intolerance and constitutively high levels of circulating corticosterone, suggesting reduced glucocorticoid suppression of the hypothalamic-pituitary-adrenal axis coupled with increased sensitivity to the hyperglycemic effects of glucocorticoid-mediated transactivation in the liver. Cry1 and Cry2 association with a GRE in the Pck1 promoter was stimulated by Dex, and Dex-induced transcription of pck1 was strikingly increased in Cry-deficient livers. Finally, cry1-/-;cry2-/- mice subjected to 8 weeks of chronic Dex treatment exhibited incomplete suppression of circulating corticosterone and greater glucose intolerance compared with wildtype littermates subjected to the same chronic treatment, consistent with enhanced transcriptional response to the synthetic glucocorticoid ligand.

ORGANISM(S): Mus musculus

PROVIDER: GSE24469 | GEO | 2011/12/22

SECONDARY ACCESSION(S): PRJNA132767

REPOSITORIES: GEO

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Project description:Plant growth and development are strongly affected by light signals perceived by phytochromes (phy) and cryptochromes (cry). The physical interaction between photoreceptors and the cross-talk among downstream signalling steps creates a network of interactions in which the action of one photoreceptor depends on the status of the others. The processes modulated by phy and or cry include seed germination, seedling de-etiolation, plant body formation and flowering. Compared to the wild type the leaves of the phyB mutant are characterised by their extended petioles and pale colour. These features resemble the phenotype of normal plants grown under the low red to far-red ratios typical of dense plant canopies thus providing support to the idea that phyB plays a key role in the perception of high red to far-red ratios. The triple mutant lacking phyA cry1 and cry2 shows little differences in leaf size and shape with the wild typebut the quadruple phyA phyB cry1 cry2 mutant shows severely impaired leaf expansion. In addition to the specific effects on leaf sizeshape and pigmentation the phyB mutation accelerates flowering in the wild type background. This effect can be observed as a reduced number of days between sowing and visible flower buds (time scale) and as a reduced final number of leaves (developmental scale). However in the phyA cry1 cry2 triple mutant background the phyB mutation accelerates flowering on a developmental scale but severely delays flowering on a time scale. The long photoperiods inducing flowering are perceived by the leaves. Flowering signals that could include hormones and sugars migrate from the leaves to the apex in response to the light stimulus. We propose to compare the following mRNA samples of expanding leaves: 1) wild type 2) phyB mutant 3) phyA cry1 cry2 triple mutant 4) phyA phyB cry1 cry2 quadruple mutant. The comparison between the wild type and the phyB mutant will help to uncover the changes in leaf mRNA patterns underlying enhanced petiole growthreduced pigmentation and early flowering in response to the absence of phyB activity. The comparison between the phyA cry1 cry2 triple mutant and the phyA phyB cry1 cry2 quadruple mutant should reveal the mRNA differences between photosynthetic leaves with dramatically different abilities to expand. The added value of the simultaneous analysis of the two comparisons is that effect of phyB is different in both genetic backgrounds and this should provide information on the mechanisms and significance of photoreceptor interactions.

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Cryptochromes mediate rhythmic repression of the glucocorticoid receptor

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