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，实验旨在理解转录因子Islet-2（Isl 2）和特异性富含AT的DNA结合蛋白2（Satb 2）在不同类型的视网膜神经节细胞的特化中的作用 （RGC）。RGC是视网膜的输出神经元，并且在几种视网膜疾病如青光眼和视神经发育不全中受到影响。在哺乳动物视网膜中有许多功能类型的RGC，每一种都参与编码视觉场景的特定方面（例如运动、空间图案或颜色）的视网膜回路。这种功能特异性来源于不同的RGC形态和与其他细胞类型的选择性突触形成;然而，两者在发育过程中如何建立尚不清楚。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学示踪。我们专注于Isl 2和Satb 2，因为它们的表达仅限于特定的RGC类，从而表明特定的功能。 在目的1中，我们将使用形态学和生理学标准来确定哪种类型的RGC表达Isl 2和Satb 2。我们的假设是，每个TF指定一个共同的感受野性质的RGC类型，例如，Isl 2 + RGC是开和关的RGC，而Satb 2 RGC可能构成方向选择性细胞类型。目的1a是确定在限定的RGC亚组中表达GFP的小鼠中的Isl 2表达。目的1b和c一起旨在基于形态学和生理学标准对所有Isl 2 + RGC进行分类。 在目的2中，我们将通过从视网膜特异性去除Isl 2或Satb 2并通过在发育中的RGC中异位表达它们来确定Isl 2和Satb 2是否是RGC分化成其正常细胞类型所必需和足够的。然后，我们将使用各种生理和形态标准来确定所得到的RGC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遗传标记的RGC类型的结构和功能的了解来鉴定导致其分化的转录因子。 这将进一步了解发育过程中不同的视网膜回路是如何产生的;这反过来可能对了解影响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于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.