Blackshaw S, Snyder S H
Johns Hopkins University School of Medicine, Department of Neuroscience, Baltimore, Maryland 21205, USA.
J Neurosci. 1997 Nov 1;17(21):8083-92. doi: 10.1523/JNEUROSCI.17-21-08083.1997.
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.
脊椎动物存在多个视网膜外光感受器位点，但视网膜外光转导的分子基础却知之甚少。本研究报告了首个在冷血脊椎动物的直接感光松果体和副松果体中特异性表达的视蛋白的克隆。这种在沟鲶中鉴定出并命名为副视蛋白的视蛋白，定义了一个脊椎动物光色素的新基因家族，并且在大多数副松果体细胞和一部分松果体光感受器细胞中表达。副视蛋白在松果体内呈现尾到头的表达梯度。本研究还报告了编码沟鲶视紫红质和红锥色素直系同源物的部分cDNA的克隆，这是该物种视网膜视蛋白的完整组合。使用源自这些视网膜视蛋白以及副视蛋白的探针进行的原位杂交研究表明，视网膜视蛋白在松果体和副松果体器官中不表达，并且在“深部脑区”、虹膜或真皮黑素细胞中测试的任何视蛋白也不表达。这些数据表明，这些视网膜外光感受器位点的光转导必定由新的视蛋白介导。
