Influence of retinal ganglion cells on visual neuron identity in superior colliculus

摘要 人类大脑能够进行令人震惊的复杂计算，这在很大程度上要归功于大脑的多样性。 被优化以处理离散信息的特殊神经元。例如，在视觉系统中， 神经元的不同亚型被调节以区分视觉场景的各个方面，例如运动、颜色或对比度。几十年 优雅的工作已经定义了子类在许多方面，使用功能，形态和分子标准。 然而，我们对这种多样性是如何在发展中的视觉系统中产生的， 这是发展再生策略以恢复因疾病或创伤而丧失的视力的障碍。到 为了解决这一问题，我们将重点放在小鼠上级丘（SC），我们认为这是一个易于处理的模型 to开始to start开始to tackle处理this complex复杂problem问题.先前的研究已经确定了SC所需的艾德转录因子 神经发生和pakKerning，导致认为内在基因机制是SC中命运特异性的基础。 然而，与其他视觉区域相比，很少有分子被证实具有这种作用（例如re 8 na或 而且，我们先前和初步的数据挑战了这一观点，揭示了视网膜神经节的潜在作用。 细胞（RGC）以命运特异性支配SC。为了测试这种可能性，我们将采用互补增益， 运用独特的基因工具，重新安排研资局投入的资源， 在不同背景下，SC和以下基因定义的神经元群体。此外，通过结合 单个神经元的形态学分析、单核RNA测序和细胞特异性体内光基因， 视觉调谐分析，我们将全面测试我们的假设。在目标1中，我们将直接确定 通过检查神经元形态学（目标1A）和转录定义的细胞多样性（目标1B） 对照组和去核小鼠的SC神经元。在目标2中，我们将利用一种独特的小鼠模型， 在SC中，Islet 2+和Islet 2- RGCs的投射被分离成不同的结构域。 这些区域的功能是不同的，可能是神经元功能的转换。为了验证这种可能性，我们 将决定基因的视觉调谐特性（Aim 2A）、形态学（Aim 2B）和转录组（Aim 2C）， 在Islet 2 +-和Islet 2--RGC支配的SC区域中定义的SC神经元群。 这些实验将大大促进我们对细胞多样性产生机制的理解， 揭示了外源性突触输入在形成神经元突触中潜在范式转换作用。

ABSTRACT The human brain is capable of making astoundingly complex computa8ons thanks in large part to the diversity of specialized neurons that are op8mized to processes discrete bits of informa8on. For example, in the visual system, different subtypes of neurons are tuned to dis8nct aspect of the visual scene, such as mo8on, color or contrast. Decades of elegant work has defined the subclasses in many ways, using func8onal, morphological, and molecular criteria. However, we have a poor understanding of how such diversity arises in the developing visual system, crea8ng a roadblock to the development of regenera8ve strategies to restore vision aCer loss due to disease or trauma8c injury. To address this gap, we will focus on the mouse superior colliculus (SC) in this proposal, which we posit is a tractable model to begin to tackle this complex problem. Previous studies have iden8fied transcrip8on factors required for SC neurogenesis and paKerning, leading to the view that intrinsic gene8c mechanisms underlie fate specifica8on in the SC. However, very few molecules have been iden8fied to have this role in comparison to other visual regions (e.g. re8na or visual cortex); and, our previous and preliminary data challenge this no8on, revealing a poten8al role for re8nal ganglion cells (RGCs) innerva8ng the SC in fate specifica8on. To test this exci8ng possibility, we will take complementary gain- and loss-of-func8on approaches, leveraging unique gene8c tools that allow us to rearrange the organiza8on of RGC inputs to the SC and follow gene8cally-defined neuronal popula8ons in different contexts. Furthermore, by combining morphological analyses of individual neurons, single nucleus RNA sequencing, and cell-specific in vivo optogene8cs with visual tuning analysis, we will comprehensively test our hypothesis. In Aim 1, we will directly determine the role of re8nal input by examining neuronal morphology of (Aim 1A) and the transcrip8onally-defined cellular diversity (Aim 1B) of SC neurons from control and enucleated mice. In Aim 2, we will leverage a unique mouse model in which the projec8ons of Islet2+ and Islet2- RGCs are segregated into different domains in the SC. Previously, we showed that visual func8on was divergent in these regions, sugges8ng poten8al switching of neuronal iden8ty. To test this possibility, we will determine the visual tuning proper8es (Aim 2A), morphology (Aim 2B), and transcriptome (Aim 2C) of gene8cally- defined SC neuron popula8ons in Islet2+- and Islet2--RGC innervated regions of the SC. Taken together, these experiments will significantly advance our understanding of the mechanisms by which cellular diversity is generated in the SC and uncover a poten8ally paradigm-shiCing role for extrinsic synap8c inputs in shaping neuronal iden8ty.