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Science 306 (5693): 129-131

Copyright © 2004 by the American Association for the Advancement of Science

Nonvisual Photoreception in the Chick Iris

Daniel C. Tu,1 Matthew L. Batten,3 Krzysztof Palczewski,3,4 Russell N. Van Gelder1,2*

Abstract: The embryonic chicken iris constricts to light ex vivo, but with characteristics atypical of visual phototransduction. The chick iris was most sensitive to short-wavelength light, demonstrating an action spectrum consistent with cryptochrome rather than with opsin pigments. Pupillary responses did not attenuate after saturating light exposure, but showed paradoxical potentiation. Iris photosensitivity was not affected by retinoid depletion or inhibitors of visual phototransduction. Knockdown of cryptochrome expression, but not of melanopsin expression, decreased iris photosensitivity. These data characterize a non-opsin photoreception mechanism in a vertebrate eye and suggest a conserved photoreceptive role for cryptochromes in vertebrates.

1 Department of Ophthalmology and Visual Sciences, Washington University Medical School, St. Louis, MO 63110 USA.
2 Department of Molecular Biology and Pharmacology, Washington University Medical School, St. Louis, MO 63110 USA.
3 Department of Ophthalmology, University of Washington, Seattle, WA 98195 USA.
4 Departments of Pharmacology and Chemistry, University of Washington, Seattle, WA 98195 USA.

* To whom correspondence should be addressed. E-mail: Vangelder{at}

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