Parapinopsin, a novel catfish opsin localized to the parapineal organ, defines a new gene family.
Multiple sites of extraretinal photoreception are present in vertebrates, but the molecular basis of extraretinal phototransduction is poorly understood. This study reports the cloning of the first opsin specifically expressed in the directly photosensitive pineal and parapineal of cold-blooded vertebrates. This opsin, identified in channel catfish and termed parapinopsin, defines a new gene family of vertebrate photopigments and is expressed in a majority of parapinealocytes and a subset of pineal photoreceptor cells. Parapinopsin shows a caudal-rostral gradient of expression within the pineal organ. This study also reports the cloning of partial cDNAs encoding the channel catfish orthologues of rhodopsin and the red cone pigment-the full complement of retinal opsins in the species. In situ hybridization studies using probes derived from these retinal opsins, together with parapinopsin, reveal no expression of retinal opsins in pineal and parapineal organ and no expression of any opsin tested in the "deep brain," iris, or dermal melanophores. These data imply that phototransduction in these sites of extraretinal photoreception must be mediated by novel opsins.
Blackshaw
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Johns Hopkins University School of Medicine, Department of Neuroscience, Baltimore, Maryland 21205, USA.
Snyder
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D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005136:Eye Proteins / Q000737:chemistry; D029941:Fish Proteins; D005786:Gene Expression Regulation; D005796:Genes; D006054:Goldfish; D007059:Ictaluridae / Q000235:genetics*; D008547:Melanophores / Q000737:chemistry; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity; D010786:Photoreceptor Cells / Q000737:chemistry*; D010802:Phylogeny; D010870:Pineal Gland / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D012160:Retina / Q000737:chemistry; D017299:Rod Opsins / Q000737:chemistry / Q000235:genetics*; D012679:Sense Organs / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D013650:Taste Buds / Q000737:chemistry
D018076:DNA, Complementary; D005136:Eye Proteins; D029941:Fish Proteins; D017299:Rod Opsins; C095855:long-wavelength opsin; C108815:parapinopsin protein, Ictalurus punctatus