VA Opsin-Based Photoreceptors in the Hypothalamus of Birds
VA Opsin-Based Photoreceptors in the Hypothalamus of Birds
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DOI：
10.1016/j.cub.2009.06.066
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发表时间：
2009-08-25
期刊：
影响因子：
9.2
通讯作者：
Foster, Russell G.
中科院分区：
文献类型：
--
作者：
Halford, Stephanie;Pires, Susana S.;Foster, Russell G.
20世纪30年代的研究表明，鸟类拥有位于下丘脑的光感受器，并调节光周期对日长的反应[1，2]。最近，光周期被证明可以改变结节部释放促甲状腺激素的活性，最终驱动生殖反应[3，4]。尽管有这些重要的发现，但下丘脑光感受器的细胞和分子身份仍然是一个谜。作用光谱暗示了一种基于视蛋白的光致变色系统[5]，但基于杆状或锥形视蛋白探针的进一步鉴定失败，表明利用了一种新的视蛋白[6]。脊椎动物古代(VA)视光色素于1997年被分离出来[7，8]，但被认为有一个有限的分类分布，仅限于无脊椎动物和硬骨鱼。在这里，我们报道了从鸡中分离出VA视蛋白，并证明了从该基因拼接的两个亚型(cVAL和CVA)能够形成功能性感光色素。此外，我们发现VA视蛋白在下丘脑神经元中表达，这些神经元广泛投射到正中隆起。这些结果提供了所有脊椎动物中最完整的大脑深层光感受器的细胞和分子描述，并强烈暗示VA视蛋白参与了鸟类的光周期反应。
Studies in the 1930s demonstrated that birds possess photoreceptors that are located within the hypothalamus and regulate photoperiodic responses to day length [1, 2]. Most recently, photoperiod has been shown to alter the activity of the pars tuberalis to release thyrotrophin, which ultimately drives a reproductive response [3, 4]. Despite these significant findings, the cellular and molecular identity of the hypothalamic photoreceptors has remained a mystery. Action spectra implicated an opsin-based photopigment system [5], but further identification based on rod- or cone-opsin probes failed, suggesting the utilization of a novel opsin [6]. The vertebrate ancient (VA) opsin photopigments were isolated in 1997 [7, 8] but were thought to have a restricted taxonomic distribution, confined to the agnatha and teleost fish. Here, we report the isolation of VA opsin from chicken and show that the two isoforms spliced from this gene (cVAL and cVA) are capable of forming functional photopigments. Further, we show that VA opsin is expressed within a population of hypothalamic neurons with extensive projections to the median eminence. These results provide the most complete cellular and molecular description of a deep brain photoreceptor in any vertebrate and strongly implicate VA opsin in mediating the avian photoperiodic response.