LIGHT-TRANSDUCTION IN MELANOPSIN-EXPRESSING PHOTORECEPTORS OF AMPHIOXUS Mechanistic analysis and evolutionary implications

“这项奖励是根据2009年美国复苏和再投资法案（公法111-5）资助的。”动物视觉传统上被认为是由两种不同的感觉细胞组成的，它们分别在脊椎动物和无脊椎动物中进化。这些光感受器在光传感器结构和将捕获的光子转化为电信号的生物化学方面有着根本的不同。这种观点受到了其他光探测方案的发现和所有光感受器可能有共同起源的线索的挑战。一个关键的发现是发现了一种新的感光哺乳动物细胞，这种细胞通过一种类似于无脊椎动物的光子捕获分子黑视素来调节生物钟。然而，这些动物群体之间的巨大差异使得比较分析变得困难，由于哺乳动物细胞的稀缺性，表征黑视素信号传导的困难加剧了比较分析。这种僵局可以通过研究一些现代脊椎动物的前身来缓解，以弥合这一进化鸿沟。文昌鱼提供了独特的优势，因为基因组研究表明它是最基础的活脊索动物，并保持接近其祖先的状态。因此，它提供了一个有利的窗口来检查生物机制，因为它们可能已经存在，当脊椎动物分支分离。在一些可识别的文昌鱼细胞中检测到黑视素，但没有进行功能研究；研究人员将利用他们的初步结果，证明分离这些细胞和测量光致电反应的可行性。该项目将在伍兹霍尔的海洋生物实验室招募和培训研究生。海洋生物实验室为这项工作提供了良好的环境。多管齐下的方法将表征光响应机制，确定刺激-响应耦合的中间步骤，并启动它们的分子表征。其好处将是双重的：有助于阐明光感的进化，并阐明黑视素的信号机制，这在很大程度上仍然是难以捉摸的。该项目的多学科性质为培养年轻的研究人员提供了肥沃的土壤，使他们接触到从进化生物学到感觉生理学和细胞生物物理学的问题；技术库将相应地多样化，包括电子和光学记录、分子和免疫识别以及生物信息学工具。

"This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5)."Animal vision was traditionally thought to be comprised of two distinct lineages of sensory cells that evolved separately in vertebrates vs. invertebrates. These photoreceptors differ fundamentally in the light sensor structure and the biochemistry to convert captured photons into electrical signals. Such view was challenged by the discovery of additional light-detection schemes and by clues pointing to a likely common origin for all photoreceptors. One pivotal finding was the identification of novel light-sensitive mammalian cells, which regulate the biological clock via a photon-capturing molecule, melanopsin, akin to those of invertebrates. However, the enormous divergence between these groups of animals makes comparative analysis arduous, exacerbated by the difficulties to characterize melanopsin-signaling in mammalian cells, owing to their scarcity. This impasse could be alleviated by examining some precursor of modern vertebrates, to bridge this evolutionary chasm. Amphioxus offers unique advantages, because genomic research established that it is the most basal living chordate and has remained close to its ancestral condition. It thus provides a favorable window to examine biological mechanisms as they may have existed when the vertebrate branch separated. Melanopsin has been detected in some identifiable amphioxus cells, but no functional study had been conducted; the investigators will capitalize on their initial results, demonstrating the feasibility to isolate these cells and measure light-induced electrical responses. The project will recruit and train graduate students at the Marine Biological Laboratory in Woods Hole. The Marine Biological Laboratory provides an outstanding environment for this work. A multi-pronged approach will characterize the photoresponse mechanisms, identify intermediate steps of stimulus-response coupling, and initiate their molecular characterization. The benefits will be two-fold: help clarify the evolution of light-sensing, and elucidate melanopsin signaling mechanisms, which remain largely elusive. The multi-disciplinary nature of the project provides a fertile ground to train young investigators, exposing them to issues ranging from evolutionary biology to sensory physiology and cellular biophysics; the technical arsenal will be correspondingly diverse, encompassing electrical and optical recording, molecular and immunological identification, and bio-informatics tools.