Non-rod, non-cone photoreception in rodents and teleost fish.
Until recently, all ocular photoreception was attributed to the rods and cones of the retina. However, studies on mice lacking rod and cone photoreceptors (rd/rd cl), has shown that these mice can still use their eyes to detect light to regulate their circadian rhythms, suppress pineal melatonin, modify locomotor activity and modulate pupil size. In addition, action spectra for some of these responses have characterized a novel opsin/vitamin A-based photopigment with a lambda(max) approximately 480 nm. Electrophysiological studies have shown that a subset of retinal ganglion cells are intrinsically photosensitive, and melanopsin has been proposed as the photopigment mediating these responses to light. In contrast to mammals, an inner retinal photopigment gene has been identified in teleost fish. Vertebrate ancient (VA) opsin forms a photopigment with a lambda(max) between 460-500 nm, and is expressed in a sub-set of retinal horizontal cells, and cells in the amacrine and ganglion cell layers. Electrophysiological analysis suggests that VA opsin horizontal cells are intrinsically photosensitive and encode irradiance information. In contrast to mammals, however, the function of these novel ocular photoreceptors remains unknown. We compare non-rod, non-cone ocular photoreceptors in mammals and fish, and examine the criteria used to place candidate photopigment molecules into a functional context.
Foster
Russell G
RG
Department of Integrative and Molecular Neuroscience, Division of Neuroscience and Psychological Medicine, Imperial College Faculty of Medicine, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK.
Hankins
Mark
M
Lucas
Robert J
RJ
Jenkins
Aaron
A
Muñoz
Marta
M
Thompson
Stewart
S
Appleford
Joanne M
JM
Bellingham
James
J
D000595:Amino Acid Sequence; D000818:Animals; D005399:Fishes; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D051381:Rats; D012168:Retinal Pigments / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D017299:Rod Opsins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D017386:Sequence Homology, Amino Acid
D012168:Retinal Pigments; D017299:Rod Opsins