PMID:20174658

Citation	Kubo, Y, Takeuchi, T, Okano, K and Okano, T (2010) Cryptochrome genes are highly expressed in the ovary of the African clawed frog, Xenopus tropicalis. PLoS ONE 5:e9273
Abstract	Cryptochromes (CRYs) are flavoproteins sharing high homology with photolyases. Some of them have function(s) including transcription regulation in the circadian clock oscillation, blue-light photoreception for resetting the clock phase, and light-dependent magnetoreception. Vertebrates retain multiple sets of CRY or CRY-related genes, but their functions are yet unclear especially in the lower vertebrates. Although CRYs and the other circadian clock components have been extensively studied in the higher vertebrates such as mice, only a few model species have been studied in the lower vertebrates. In this study, we identified two CRYs, XtCRY1 and XtCRY2 in Xenopus tropicalis, an excellent experimental model species. Examination of tissue specificity of their mRNA expression by real-time PCR analysis revealed that both the XtCRYs showed extremely high mRNA expression levels in the ovary. The mRNA levels in the ovary were about 28-fold (XtCry1) and 48-fold (XtCry2) higher than levels in the next abundant tissues, the retina and kidney, respectively. For the functional analysis of the XtCRYs, we cloned circadian positive regulator XtCLOCK and XtBMAL1, and found circadian enhancer E-box in the upstream of XtPer1 gene. XtCLOCK and XtBMAL1 exhibited strong transactivation from the XtPer1 E-box element, and both the XtCRYs inhibited the XtCLOCK:XtBMAL1-mediated transactivation, thereby suggesting this element to drive the circadian transcription. These results revealed a conserved main feedback loop in the X. tropicalis circadian clockwork and imply a possible physiological importance of CRYs in the ovarian functions such as synthesis of steroid hormones and/or control of estrus cycles via the transcription regulation.
Links	PubMed PMC2822860 Online version:10.1371/journal.pone.0009273
Keywords	ARNTL Transcription Factors/genetics; Animals; CLOCK Proteins/genetics; Cell Line; Cell Nucleus/metabolism; Cryptochromes/classification; Cryptochromes/genetics; Cryptochromes/metabolism; E-Box Elements/genetics; Female; Gene Expression Profiling; Green Fluorescent Proteins/genetics; Green Fluorescent Proteins/metabolism; Humans; Kidney/metabolism; Male; Microscopy, Fluorescence; Ovary/metabolism; Period Circadian Proteins/genetics; Phylogeny; Protein Isoforms/genetics; Protein Isoforms/metabolism; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Retina/metabolism; Reverse Transcriptase Polymerase Chain Reaction; Transcriptional Activation; Xenopus/genetics; Xenopus/metabolism; Xenopus Proteins/classification; Xenopus Proteins/genetics; Xenopus Proteins/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XENTR:F6WSJ3		GO:0005634: nucleus	ECO:0000314:		C		Xenopus tropicalis CRY2. Both GFP-CRY1 and GFP-CRY2 localized in the nucleus, while GFP alone localized predominantly in the cytoplasm (Figure 4).	complete CACAO 12877

References

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