Structural and molecular determinants of duplex functionality in a pure-rod retina

项目摘要/摘要： 双眼视网膜的正常功能取决于视杆细胞和视锥细胞在加工 照明的暗视和明视范围内的视觉信息。重要的是，当任何一种类型的 光感受器在视网膜变性过程中丢失，剩下的光感受器，无论是视杆细胞还是视锥细胞，都不能 执行相反单元格类型的功能。大多数脊椎动物的视网膜都有这种“二元性”屏障 目前的视力恢复努力的目标是取代丢失的光感受器群体。然而， 弹力木(ElasmoBranch L.erinacea)(Little Skate)的视网膜是单视杆的，它可以在暗视下和 照相照明。我们很难理解是什么因素导致了这种非凡的可塑性 滑行视网膜，但对如何实现这一点的详细了解可能是扩大功能的关键 病变双眼视网膜中存活的视杆细胞或视锥细胞的谱系。我们认为滑冰的视网膜表现出一种 在分子和超微结构水平上调节其功能可塑性的许多杂交特征。 此外，我们的初步数据使我们得出两个主要假设：1)滑冰杆在暗视下的功能和 通过在突触终末水平上的形态适应的组合， 和视蛋白表达水平的遗传适应；以及：2)滑冰视网膜表现出多种适应 杆下游的细胞电路，以适应其功能可塑性。我们已经建立了 这些预测基于几项初步数据。首先，长波敏视蛋白(LWS)可以 在溜冰鞋的全球基因组中检测到。第二，在超微结构中表现出多种杂交特征 滑冰杆突触末端的水平。第三，突触后的数量增加了3倍 内陷到滑冰杆末端的过程，与来自双眼视网膜的杆相比。因此，我们将 在以下特定目标中测试我们的假设：目标1：分析光下基因表达的差异- 和暗适应的纯视杆视网膜，并揭示功能可塑性的分子机制。的目标是 目的1是确定是什么分子因素介导了这种不寻常的功能可塑性。目标2：确定 细胞和电路水平的结构和生理特性对调节功能的贡献 纯杆状视网膜的可塑性。目标2的目的是确定滑冰棒是否具有超微结构 调节其功能可塑性的元素，以及视杆下游的视网膜电路是否已经进化 特定的结构和生理属性，以适应更大范围的输入。这个 提出的研究是创新的，因为单纯性滑冰视网膜已经自然进化到现在的状态 并允许我们有独特的机会来研究和描述杆电路的特性 这是一种经过进化优化的视觉系统，不像转基因的杆状模型。这一点意义重大，因为 它将揭示自然产生的单型视网膜的功能适应的基本原理，这是 可能导致视力恢复方面的新方法，特别是在选择性丧失光感受器之后。

PROJECT SUMMARY/ABSTRACT: Proper function in the duplex retina depends on the utilization of rods and cones in the processing of visual information across the scotopic and photopic ranges of illumination. Importantly, when either type of photoreceptor is lost during retinal degeneration, the remaining photoreceptors, be they rods or cones, cannot perform the function of the opposite cell type. Most vertebrate retinae have this “duality” barrier and many current vision restoration efforts are targeted towards replacing the lost photoreceptor population. However, the elasmobranch L. erinacea (Little skate) has a pure-rod simplex retina, which can function under scotopic and photopic illumination. We have a poor understanding of what factors govern this remarkable plasticity in the skate retina, but a detailed knowledge of how this is achieved could hold the key to expanding the functional repertoire of surviving rods or cones in diseased duplex retinae. We propose that the skate retina exhibits a number of hybrid features on the molecular and ultrastructural levels that mediate its functional plasticity. Furthermore, our preliminary data leads us to two main hypotheses: 1) Skate rods function under scotopic and photopic conditions through a combination of morphological adaptations at the level of the synaptic terminal, and genetic adaptations at the level of opsin expression; and: 2) The skate retina exhibits multiple adaptions in the cell circuitry downstream of rods in order to accommodate for their functional plasticity. We have based these predictions on several pieces of preliminary data. First, a long-wavelength sensitive opsin (LWS) can be detected in the global genome of the skate. Second, multiple hybrid features are present at the ultrastructural level in the synaptic terminals of the skate rods. Third, there is a 3-fold increase in the number of postsynaptic processes that invaginate into a skate rod terminal, compared to rods from duplex retinae. Therefore, we will test our hypotheses in the following specific aims: Aim 1: To analyze differences in gene expression in light- and dark-adapted pure-rod retinae and uncover molecular mechanisms of functional plasticity. The objective of Aim 1 is to determine what molecular factors mediate this unusual functional plasticity. Aim 2: To determine the contribution of cell- and circuit-level structural and physiological characteristics mediating functional plasticity in a pure-rod retina. The objectives of Aim 2 are to determine if skate rods posses ultrastructural elements that mediate their functional plasticity, and if the retinal circuitry downstream of rods has evolved specific structural and physiological attributes in order to accommodate for a wider range of inputs. The proposed research is innovative because the simplex skate retina has evolved naturally to the present state and allows us the unique opportunity to study and describe the properties of rod circuitry within the context of an evolutionarily optimized visual system, unlike genetically modified rod-only models. It is significant because it will reveal fundamental principles of functional adaptation in a naturally occurring monotypic retina, which may lead to novel approaches in vision restoration efforts, especially after selective loss of photoreceptors.