Nonvisual photoreception in the chick iris.
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.
Department of Ophthalmology and Visual Sciences, Washington University Medical School, St. Louis, MO 63110 USA.
Daniel C
DC
Tu
Matthew L
ML
Batten
Krzysztof
K
Palczewski
Russell N
RN
Van Gelder
D000818:Animals; D002642:Chick Embryo; D056931:Cryptochromes; D005420:Flavoproteins / Q000235:genetics / Q000502:physiology*; D007498:Iris / Q000196:embryology* / Q000502:physiology*; D008027:Light; D055537:Light Signal Transduction / Q000187:drug effects; D034741:RNA, Small Interfering; D012025:Reflex, Pupillary; D012176:Retinoids / Q000032:analysis / Q000502:physiology; D017299:Rod Opsins / Q000235:genetics / Q000502:physiology; D014466:Ultraviolet Rays; D000099210:Melanopsin
D056931:Cryptochromes; D005420:Flavoproteins; D034741:RNA, Small Interfering; D012176:Retinoids; D017299:Rod Opsins; D000099210:Melanopsin