Structure & Function of Ganglion-Cell Photoreceptors Contributing to Form Vision

描述(由申请人提供)： 自从发现一种新型的视网膜色素黑素以来，仅仅过去了十年，这种新的视网膜色素黑素在一小部分视网膜神经节细胞中表达，称为固有光敏性视网膜神经节细胞(IpRGCs)。这一领域的快速发展已经将这些细胞与调节生物钟、瞳孔反射、神经内分泌和情绪的季节性变化联系在一起。经典观点认为，ipRGC的功能贡献仅限于这些纯粹的反射性、内稳态和非成像作用。然而，最近发现了各种新的ipRGC，它们向大脑中涉及对形状、运动和颜色的有意识视觉感知的区域发送信号。本研究的目的是首次系统地描述这些新的基于黑素的视觉通道(S)投射到大脑的成像中心的形式和功能。具体目标1将描述投射到脑的两个成像视觉中枢--丘脑背外侧膝状核(DLGN)和上丘(SC)的ipRGC的形态。这样的结构数据将允许识别哪些ipRGC亚型参与这一通道，但也将形成一个重要的描述性基础，以确定这些细胞的突触关系。具体目标2将描述投射到dLGN和SC的ipRGC的生理特性。这些研究将有助于确定这一神秘知觉通道的独特属性。为了识别感兴趣的细胞，将使用在ipRGC中选择性表达GFP的转基因小鼠，并使用对比鲜明的逆行轴突示踪剂标记那些具有膝曲或丘状投射的细胞。这只是实现这些目标所使用的众多技术之一，使该项目成为理想的培训场所。其他包括膜片钳记录、细胞内染料填充、免疫组织化学、轴突运输追踪、感受野分析、突触药理学和共聚焦显微镜。这些研究将为黑素蛋白和辐射编码的ipRGC对正常视觉知觉机制的功能贡献提供更广泛和更完整的图景。鉴于ipRGC在人体对日光的反应中扮演的关键角色，这些研究与时差、季节性情感障碍和轮班工作时的警觉性等公共健康问题有关。此外，这项工作可能会为患有视网膜外部疾病的眼盲患者的剩余视力提供新的线索，例如视网膜色素变性、老年性黄斑变性或Leber先天性黑色素，在这些疾病中，视网膜内部基本上是幸免于难的。对这些个体中残留的神经节细胞光接收的新理解可能被利用来开发临床治疗和改善生活。 公共卫生相关性： 这个项目的目标是研究哺乳动物视网膜的特殊输出细胞的结构和功能，这些细胞可以将光能转化为神经信号。此前，这类细胞被认为可以调节对光线的无意识反应，比如调节生物钟、某些荷尔蒙的水平以及眼睛的瞳孔大小。我们最近发现了这类细胞的新变种，它们向涉及有意识视觉感知的大脑区域发送信号。在这里，我们将第一次系统地描述这些细胞的形式和功能。由于这些细胞在人体对日光的反应中扮演着关键角色，这些研究与时差和季节性情感障碍等公共健康问题有关，也与眼盲人群中可用于新的临床治疗的剩余视觉能力有关。

DESCRIPTION (provided by applicant): Only a decade has elapsed since the discovery of the novel retinal photopigment melanopsin expressed in a small subset of retinal ganglion cells, called intrinsically photosensitive retinal ganglion cells (ipRGCs). Rapid progress in this field has linked these cells to the regulation the circadian clock, the pupillary reflex, neuroendocrine secretions, and seasonal variations of mood. The canonical view has been that the functional contributions of ipRGCs are limited to these purely reflexive, homeostatic, and non-image forming roles. However, new varieties of ipRGCs have recently been discovered that send signals to brain regions involved in conscious visual perception of form, motion and color. The goal of this study is to provide the first systematic description of the form and function of these novel melanopsin-based visual channel(s) projecting to image- forming centers of the brain. Specific Aim 1 will characterize the morphology of ipRGCs projecting to two image-forming visual centers of the brain - the dorsal lateral geniculate nucleus of the thalamus (dLGN) and the superior colliculus (SC). Such structural data will permit the identification of which ipRGC subtypes participate in this channel, but will also form a crucial descriptive foundation for working out the synaptic relationships of these cells. Specific Aim 2 will characterize the physiological properties of the ipRGCs that project to the dLGN and SC. These studies will help define the unique attributes of this enigmatic perceptual channel. To identify the cells of interest, a genetically modified mouse with selective expression of GFP in ipRGCs will be used, and a contrasting retrograde axon tracer will label those that have geniculate or collicular projections. This will be just one of many techniques utilized in the pursuit of these aims, making this project an ideal training venue. Others include patch clamp recording, intracellular dye filling, immunohistochemistry, axon transport tracing, receptive field analysis, synaptic pharmacology, and confocal microscopy. These studies will provide a broader and more complete picture of the functional contribution of melanopsin and irradiance-encoding ipRGCs to normal visual perceptual mechanisms. Given the key role that ipRGCs play in the body's responses to daylight, these studies are relevant to such public health issues as jet lag, seasonal affective disorder, and alertness during shift work. In addition, this work may be shed new light on residual visual capacities in ocularly blind patients with outer retinal diseases, such as retinitis pigmentosa, age-related macular degeneration or Leber's congenital amaurosis, in which the inner retina is largely spared. New understanding of residual ganglion cell photoreception in these individuals might be harnessed to develop clinical treatments and improve lives. PUBLIC HEALTH RELEVANCE: The goal of this project is to study the structure and function of specialized output cells of the mammalian retina that can convert light energy into neural signals. Such cells have previously been thought to regulate unconscious responses to light, such as adjusting the biological clock, the levels of certain hormones, and the size of the eye's pupil. We have recently discovered new varieties of such cells that send signals to brain regions involved in conscious visual perception. Here we will provide the first systematic description of the form and function of these cells. Because of the key role these cells play in the body's responses to daylight, these studies are relevant to such public health issues as jet lag and seasonal affective disorder, as well as residual visual capacities in the ocularly blind population that can be harnessed for new clinical treatments.