Development of retinal ganglion cell types

描述(由申请人提供)：本提案的目标是了解用于创建哺乳动物视网膜回路的机制。具体地说，实验旨在了解转录因子Islet-2(Isl2)和特定的富含AT的DNA结合蛋白2(Satb2)在指定不同类型的视网膜神经节细胞中的作用 (RGCs)。视网膜节细胞是视网膜的输出神经元，在几种视网膜疾病中受到影响，如青光眼和视神经发育不良。在哺乳动物的视网膜中有许多功能类型的RGC，每一种都参与一个视网膜回路，该回路编码视觉场景的一个特定方面，如运动、空间模式或颜色。这种功能特异性来自不同的RGC形态和与其他类型细胞的选择性突触形成；然而，这两者是如何在发育过程中建立的仍不清楚。我们的实验结合了小鼠转基因技术、体内生理电记录和成像技术以及解剖示踪技术。我们关注Isl2和Satb2，因为它们的表达被限制在特定的RGC类，从而暗示了特定的功能。在目标1中，我们将使用形态和生理标准来确定哪些类型的视网膜节细胞表达Is12和Satb2。我们的假设是，每个Tf指定RGC类型的一个共同的感受场属性；例如，Is12+RGC是开和关的RGC，而Satb2 RGC可能构成方向选择性细胞类型。目的1a确定在已定义的RGC亚群中表达GFP的小鼠中Isl2的表达。目标1b和c共同致力于根据形态和生理标准对所有Is12+RGC进行分类。在目标2中，我们将通过从视网膜中专门去除Isl2或Satb2，并通过在发育中的RGC中异位表达它们，来确定Isl2和Satb2是否是RGC分化为正常细胞类型的必要条件和充分条件。然后，我们将使用各种生理和形态标准来确定所产生的视网膜节细胞的形态和生理特性。我们研究RGC分化的方法将利用我们对不同基因标记的RGC类型的结构和功能的知识来识别导致它们分化的转录因子。 这将进一步加深我们对不同视网膜回路在发育过程中如何产生的理解；这反过来可能对理解影响RGC功能的疾病的后果有实际好处。此外，治疗视网膜疾病的成功疗法将取决于 修复受损的视觉回路，使这些回路的发展知识对设计治疗策略和评估功能恢复至关重要。

DESCRIPTION (provided by applicant): The goal of this proposal is to understand the mechanisms used to create the circuitry of the mammalian retina. Specifically, experiments are aimed toward understanding the role of the transcription factors Islet-2 (Isl2) and specific AT-rich DNA-binding protein 2 (Satb2) in the specification of distinct types of retinal ganglion cells (RGCs). RGCs are the output neurons of the retina and are affected in several retinal diseases such as glaucoma and optic nerve hypoplasias. There are numerous functional types of RGCs in the mammalian retina, each participating in a retinal circuit that encodes a specific aspect of the visual scene, such as motion, spatial patterns, or color. This functional specificity is derive from distinct RGC morphology and selective synapse formation with other cell types; however, how both are established during development remains unclear. Our experiments use a combination of mouse transgenic technology, in vivo physiological electrical recording and imaging techniques, and anatomical tracing. We focus on Isl2 and Satb2 because their expression is restricted to specific RGC classes, thereby suggesting a specific function. In Aim 1 we will determine which types of RGCs express Isl2 and Satb2 using both morphological and physiological criteria. Our hypothesis is that each TF specifies a common receptive field property of RGC types; for example, that Isl2+ RGCs are On and Off RGCs, while Satb2 RGCs may constitute direction selective cell types. Aim 1a is to determine Isl2 expression in mice expressing GFP in defined RGC subsets. Aims 1b and c together aim to classify all Isl2+ RGCs based on morphological and physiological criteria. In Aim 2 we will determine if Isl2 and Satb2 are necessary and sufficient for the RGCs to differentiate into their normal cell types by specifically removing Isl2 or Satb2 from the retina and by ectopically expressing them in developing RGCs. We will then determine the morphological and physiological properties of the resulting RGCs using a variety of physiological and morphological criteria. Our approach to study RGC differentiation will use our knowledge of the structure and function of different genetically-labeled RGC types to identify transcription factors that lead to their differentiation. This will further our understanding of how different retinal circuits arise during development; thi in turn is likely to have practical benefits in understanding the consequences of diseases that affect RGC function. In addition, successful therapies for treating retinal diseases will depend on the restoration of damaged visual circuits, making knowledge of the development of these circuits essential for designing therapeutic strategies and assessing functional recovery.