An Extraretinally Expressed Insect Cryptochrome with Similarity to the Blue Light Photoreceptors of Mammals and Plants

Photic entrainment of insect circadian rhythms can occur through either extraretinal (brain) or retinal photoreceptors, which mediate sensitivity to blue light or longer wavelengths, respectively. Although visual transduction processes are well understood in the insect retina, almost nothing is know...

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Bibliographic Details
Published in:	The Journal of neuroscience 1999-05, Vol.19 (10), p.3665-3673
Main Authors:	Egan, Elizabeth S, Franklin, Tina M, Hilderbrand-Chae, Marla J, McNeil, Gerard P, Roberts, Mary A, Schroeder, Andrew J, Zhang, Xiaolan, Jackson, F. Rob
Format:	Article
Language:	eng
Subjects:	Amino Acid Sequence Animals Biological Clocks Brain - metabolism Chromosome Mapping Circadian Rhythm - physiology Cryptochromes Drosophila Drosophila Proteins Eye Proteins Flavoproteins - chemistry Genes, Insect Humans Insect Proteins - chemistry Mice Molecular Sequence Data Oscillometry Photoreceptor Cells, Invertebrate - chemistry Photosynthetic Reaction Center Complex Proteins - chemistry Receptors, G-Protein-Coupled RNA, Messenger - biosynthesis Sequence Homology, Amino Acid
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Summary:	Photic entrainment of insect circadian rhythms can occur through either extraretinal (brain) or retinal photoreceptors, which mediate sensitivity to blue light or longer wavelengths, respectively. Although visual transduction processes are well understood in the insect retina, almost nothing is known about the extraretinal blue light photoreceptor of insects. We now have identified and characterized a candidate blue light photoreceptor gene in Drosophila (DCry) that is homologous to the cryptochrome (Cry) genes of mammals and plants. The DCry gene is located in region 91F of the third chromosome, an interval that does not contain other genes required for circadian rhythmicity. The protein encoded by DCry is approximately 50% identical to the CRY1 and CRY2 proteins recently discovered in mammalian species. As expected for an extraretinal photoreceptor mediating circadian entrainment, DCry mRNA is expressed within the adult brain and can be detected within body tissues. Indeed, tissue in situ hybridization demonstrates prominent expression in cells of the lateral brain, which are close to or coincident with the Drosophila clock neurons. Interestingly, DCry mRNA abundance oscillates in a circadian manner in Drosophila head RNA extracts, and the temporal phasing of the rhythm is similar to that documented for the mouse Cry1 mRNA, which is expressed in clock tissues. Finally, we show that changes in DCry gene dosage are associated predictably with alterations of the blue light resetting response for the circadian rhythm of adult locomotor activity.
ISSN:	0270-6474 1529-2401