Melanopsin: An opsin in melanophores, brain, and eye
- *Department of Anatomy and Cell Biology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814; †Institute of Cellular Signaling, University of Nijmegen, 6500 HB Nijmegen, The Netherlands; and ‡Department of Biology, The Catholic University of America, Washington, DC 20064
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Edited by Jeremy Nathans, Johns Hopkins University School of Medicine, Baltimore, MD, and approved November 5, 1997 (received for review September 16, 1997)
Abstract
We have identified an opsin, melanopsin, in photosensitive dermal melanophores of Xenopus laevis. Its deduced amino acid sequence shares greatest homology with cephalopod opsins. The predicted secondary structure of melanopsin indicates the presence of a long cytoplasmic tail with multiple putative phosphorylation sites, suggesting that this opsin’s function may be finely regulated. Melanopsin mRNA is expressed in hypothalamic sites thought to contain deep brain photoreceptors and in the iris, a structure known to be directly photosensitive in amphibians. Melanopsin message is also localized in retinal cells residing in the outermost lamina of the inner nuclear layer where horizontal cells are typically found. Its expression in retinal and nonretinal tissues suggests a role in vision and nonvisual photoreceptive tasks, such as photic control of skin pigmentation, pupillary aperture, and circadian and photoperiodic physiology.
Footnotes
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↵§ To whom reprint requests should be addressed at: Department of Anatomy, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814. e-mail: rollag{at}usuhsb.usuhs.mil.
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This paper was submitted directly (Track II) to the Proceedings Office.
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Abbreviations: RPE, retinal pigment epithelium; SCN, suprachiasmatic nucleus.
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Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF014797).
- Received September 16, 1997.
- Copyright © 1998, The National Academy of Sciences
