Role of Fat Cadherins in Neural Development of the Vertebrate Retina

项目摘要 在神经回路的组装过程中，新生的神经元迁移到特定的位置并延伸过程 以固定的方式联系合适的突触伴侣。这在脊椎动物中最为明显 视网膜由三个核层组成，中间有两个突触丛状层。 尽管这种组织的基本性质是鲜为人知的细胞机制，位置 神经元细胞类型和直接树突延伸。本研究探讨了非典型钙粘蛋白的功能， 在无长突细胞发育过程中协调这些事件的蛋白质Fat3。Fat3是一个非常大的 一种分子量约为500 Kd的钙粘蛋白分子，含有34个细胞外钙粘蛋白结构域， 在整个发育中的内丛状层（IPL）中。基因敲除小鼠的分析表明，fat3是必需的 用于引导无长突细胞树突的极化延伸进入IPL以及适当地分布 内核层（INL）和神经节细胞层（GCL）之间的无长突细胞。如果没有脂肪3 异位无长突细胞树突在IPL外精心制作，导致形成两个额外的突触。 层次。 在这个项目中，Fat3功能的分子和细胞机制将使用新的细胞系来确定。 FAT3基因敲除小鼠和条件性敲除小鼠。具体地，转基因报告基因将用于鉴定 表达Fat3的无长突细胞和神经节细胞的形态分类，并区分一般的 无长突细胞发育的功能与特定神经元回路组装的功能。 另外的体外实验将剖析控制Fat3信号传导的调节机制，包括 选择性剪接和与不同细胞质蛋白的动态相互作用。最后是神经节细胞 将分析发育，以确定Fat3是否也是形态发生和分布所必需的。 将检查这种细胞类型和中央投射，以确定Fat3是否是轴突生长所必需的。 发展虽然专注于Fat3在视网膜中的功能，但所提出的工作仍将 提供了重要的洞察脂肪钙粘蛋白在神经发育和其他系统中的作用， 它们在内耳和肾脏中高度表达。

Project Summary During the assembly of neural circuits, newly born neurons migrate to specific locations and extend processes in stereotyped manners to contact the appropriate synaptic partners. This is most evident in the vertebrate retina which is organized into three nuclear layers separated by two intervening synaptic plexiform layers. Despite the fundamental nature of this organization little is known about the cellular mechanisms that position neuronal cell types and direct dendrite extension. This study examines the function of the atypical cadherin protein Fat3 which coordinates these events during amacrine cell development. Fat3 is an unusually large cadherin molecule with a mass of ~500Kd that contains 34 extracellular cadherin domains and is present throughout the developing inner plexiform layer (IPL). Analysis of knockout mice reveals that fat3 is necessary for directing the polarized extension of amacrine cell dendrites into the IPL as well as properly distributing amacrine cells between the inner nuclear layer (INL) and the ganglion cell layer (GCL). In the absence of fat3 ectopic amacrine cell dendrites elaborate outside of the IPL resulting in the formation of two additional synaptic layers. In this project the molecular and cellular mechanism(s) of Fat3 function will be determined using novel lines of fat3 knockout and conditional knockout mice. Specifically transgenic reporters will be used to identify morphological classes of amacrine and ganglion cells expressing Fat3 and distinguish between a general function for amacrine cell development versus a function in the assembly of specific neuronal circuits. Additional in vitro experiments will dissect the regulatory mechanisms that control Fat3 signaling including alternative splicing and dynamic interactions with different cytoplasmic proteins. Finally ganglion cell development will be analyzed to determine if Fat3 is also required for the morphogenesis and distribution of this cell type, and central projections will be examined to determine if Fat3 is necessary for axonal development. Although focused on the function of Fat3 in the retina, the proposed work will nevertheless provide important insight into the role of Fat cadherins during neurodevelopment and in other systems where they are highly expressed such as the inner ear and kidney.