MOLECULAR MECHANISMS OF RETINAL CIRCUIT ASSEMBLY

视网膜电路组装的分子机制

• 批准号: 9894802
• 负责人: Daniel Kerschensteiner
• 金额: $ 38.13万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2022-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9894802
• 关键词: 3-Dimensional; Affect; Amacrine Cells; Axon; Behavior; Behavior Control; Behavioral; Behavioral Assay; Cell Adhesion Molecules; Cell Count; Cells; Complex; Data; Degenerative Disorder; Dendrites; Detection; Development; Ensure; Event; Eye Movements; Gene Delivery; Geometry; Growth; Head Movements; Image; Intuition; Knock-out; Knowledge; Lateral; Light; Link; Measures; Mediating; Molecular; Morphogenesis; Morphology; Motion; Mus; Neurites; Neurodegenerative Disorders; Neurodevelopmental Disorder; Neurons; Output; Pathway interactions; Pattern; Peripheral; Photophobia; Radial; Retina; Rod; Role; Shapes; Signal Transduction; Synapses; Testing; Variant; Vision; Visual; axon growth; base; behavioral response; cell type; functional restoration; ganglion cell; horizontal cell; insight; interdisciplinary approach; multi-electrode arrays; netrin-G1; neurite growth; neuronal circuitry; neuronal replacement; patch clamp; postsynaptic; presynaptic; receptive field; reconstruction; response; retinal neuron; retinal rods; starburst; starburst amacrine cell; synaptic function; synaptogenesis; two-photon; visual threshold

The morphology of axons and dendrites shapes the connectivity and function of neuronal circuits; and dysmorphic axons and dendrites are a common feature of neurodevelopmental disorders. To establish cell-type-specific morphologies, developing neurites need to (1) grow towards and branch in the right places (i.e. neurite targeting), (2) elaborate arbors with distinct branching patterns and geometries (i.e. neurite shape), and (3) occupy appropriate territories (i.e. neurite size). How axons and dendrites grow to an exact size, how arbor size regulates connectivity, and how it influences specific circuit computations is not well understood. In preliminary studies, we identified four cell adhesion molecules (CAMs; Amigo1, Amigo2, netrin-G1, and NGL1) that regulate dendrite and axon size of neurons in two circuits of the retina: the direction selective (DS) circuit, which extracts motion information in the inner retina, and the rod bipolar pathway, which transmits dim-light-signals from the outer to the inner retina. Starburst cells have radially symmetric arbors that overlap extensively among neighbors and express Amigo2. The central two thirds of each arbor receive input and the peripheral third provides output. Inhibitory input from starburst cells is critical for DS responses of ganglion cells. Neurite size of starburst cells is increased in Amigo2 knockout (Amigo2-/-) mice, while functional compartmentalization is maintained. In Aim 1, we will analyze the molecular mechanisms of Amigo2’s actions, test its influence on neurite morphology and connectivity, DS circuit function, and image stabilizing head and eye movements. At the first stage of the rod bipolar pathway, horizontal cell axons mediate lateral inhibition among rods, which provide input to rod bipolar dendrites. Horizontal cells express Amigo1. In Amigo1-/- mice, horizontal cell axons and rod bipolar dendrites are both reduced in size. In Aim 2, we will characterize the signaling mechanism of Amigo1, explore territory matching between synaptic partners, analyze effects on connectivity and measure light sensitivity along the rod bipolar pathway, and in behavioral responses. At the second stage of the rod bipolar pathway, netrin-G1-expressing rod bipolar axons synapse onto NGL1-expressing AII cells. Rod bipolar axon size is reduced in netrin- G1-/- and NGL1-/- mice, suggesting that retrograde signals of trans-synaptic netrin-G1/NGL1 complexes regulates axon growth. In Aim 3, we will explore whether forward signals control AII arbor size. We will determine how netrin-G1/NGL1 complexes affect the number, ultrastructure and function of synapses between rod bipolar and AII cells, and assess their influences on light responses along the rod bipolar pathway and on the ability of mice to detect dim light flashes. Together these studies will provide insights into the molecular mechanisms that control axon and dendrite size in the retina, reveal how neurite size regulates connectivity, and how it shapes specific circuit computations and influences visually guided behaviors.

轴突和树突的形态塑造了神经元电路的连通性和功能；和 营养不良的轴突和树突是神经发育障碍的常见特征。为了建立细胞型特异性形态，发展神经运动需要（1）在正确的位置生长并分支（即神经蛋白 靶向），（2）具有不同分支模式和几何形状（即神经蛋白的形状）的精心制作的乔木和（3） 占据适当的区域（即神经蛋白酶的大小）。轴突和树突如何生长到确切的尺寸，植物大小 调节连通性及其如何影响特定电路计算的方式尚不清楚。在初步 研究，我们鉴定了四个细胞粘附分子（CAM； Amigo1，Amigo2，Netrin-G1和NGL1），它们调节了 视网膜两个电路中神经元的树突和轴突大小：方向选择性（DS）电路，提取 内部视网膜和杆双极通路中的运动信息，从 外部视网膜外。 Starburst细胞具有根本对称的乔木，在邻居之间广泛重叠 并表达Amigo2。每个乔木的中央三分之二接收输入，外围三分之一提供输出。 Starburst细胞的抑制输入对于神经节细胞的DS反应至关重要。 Starburst细胞的神经突大小为 在维持功能隔室化的同时，Amigo2敲除（Amigo2 - / - ）小鼠的增加。在AIM 1中， 我们将分析Amigo2作用的分子机制，检验其对神经怪的形态的影响和 连通性，DS电路功能以及图像稳定头和眼动。在杆的第一阶段 双极途径，水平细胞轴突介导了杆之间的横向抑制，这为杆双极提供了输入 树突。水平细胞表达Amigo1。在Amigo1 - / - 小鼠中，水平细胞轴突和杆双极树突为 两者的大小都降低。在AIM 2中，我们将表征Amigo1的信号传导机制，探索区域 合成伙伴之间的匹配，分析对连通性的影响并测量沿杆的光灵敏度 双极途径和行为反应。在杆双极途径的第二阶段，表达Netrin-G1双极轴突在表达NGL1的AII细胞上。 Netrin-中杆双极轴突尺寸降低 G1 - / - 和NGL1 - / - 小鼠，表明反式突触Netrin-G1/NGL1复合物的逆行信号调节 轴突生长。在AIM 3中，我们将探索向前信号是否控制AII Arbor尺寸。我们将确定如何 Netrin-g1/ngl1复合物影响杆双极与突触的数量，超微结构和功能 AII细胞，并评估它们对沿杆双极途径的光反应的影响以及小鼠的能力 检测昏暗的光闪烁。这些研究将共同​​提供对控制分子机制的见解 视网膜中的轴突和树突大小，揭示神经蛋白的大小如何调节连通性及其形成特定的连通性 电路计算并影响视觉引导行为。