Role of the protocadherin alpha gene cluster in serotonergic circuitry formation and its implications in depressive disorders

原钙粘蛋白α基因簇在血清素能回路形成中的作用及其对抑郁症的影响

• 批准号: 9010070
• 负责人: THOMAS P MANIATIS
• 金额: $ 40万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-01-15 至 2020-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9010070
• 关键词: Address; Affective; Animals; Area; Axon; Behavior; Behavioral; Biological Neural Networks; Brain; Brain Stem; Brain region; Cadherins; Cell Adhesion; Cell Surface Proteins; Cell surface; Cells; Coculture Techniques; Cues; Depressive disorder; Development; Diagnostic; Diffuse; Diffuse Pattern; Disease; Emotional; Etiology; Family; Gene Cluster; Genes; Genetic study; Hippocampus (Brain); Individual; Knock-out; Knowledge; Label; Lead; Light; Mediating; Mental Depression; Mental disorders; Modeling; Molecular; Molecular Profiling; Mus; Nature; Nervous system structure; Neuraxis; Neurites; Neurons; Neurotransmitters; Pattern; Phenotype; Play; Presynaptic Terminals; Process; Protein Isoforms; Proteins; Proxy; Purkinje Cells; Randomized; Research; Research Design; Role; Serotonergic System; Serotonin; Site; Spatial Distribution; Specificity; Structure; Synapses; Testing; Therapeutic Intervention; Varicosity; Virus; Wild Type Mouse; Work; axon guidance; base; depressive symptoms; disability; fly; insight; loss of function; mutant; novel therapeutics; postsynaptic; presynaptic; promoter; public health relevance; raphe nuclei; receptor; relating to nervous system; research study; starburst amacrine cell; tool; transcriptome sequencing; transmission process

 DESCRIPTION (provided by applicant): The neurotransmitter serotonin is a fundamental modulator of behavior, and serotonin deficiencies lead to numerous debilitating psychiatric conditions, including depression. The number of serotonergic neurons in the nervous system is relatively small, but they modulate the activities of enormous numbers of neurons. To accomplish this, serotonergic neurons send out long-range axonal projections that diffusely arborize in virtually every region of the brain, and elaborate an expansive neural network. However, the molecular and cellular mechanism underlying serotonergic circuitry formation is largely unknown. Recent studies have shown that the protocadherin (Pcdh) α gene cluster plays an essential role in this process. The three mammalian Pcdh gene clusters (α, β, γ) encode a large family of homophilic cell surface proteins that are stochastically expressed in random combinations in individual neurons. Genetic studies have shown that Pcdhα proteins mediate dendritic repulsion and self-avoidance in a manner that is similar to that of the fly Dscam1 proteins. We generated Pcdhα cluster deletion mice and found that they display depressive-like behaviors as well as disorganized serotonergic projections, most prominently in limbic structures that mediate emotional processing. The spatial distribution of serotonergic varicosities is randomized in the absence of Pcdhα, possibly due to a loss of repulsion between serotonergic axons. In addition, serotonergic axons in Pcdhα mutants are highly enriched in certain areas of the brain and depleted in others, suggesting that a guidance mechanism is also involved. Remarkably, conditional deletion of Pcdhα genes in serotonergic neurons recapitulates the serotonergic wiring phenotype as well as depressive-like behavior. In contrast, serotonergic wiring and affective function are unchanged when the deletion is restricted in the target areas. A working model for serotonergic axonal arborization is proposed based on these observations, whereby Pcdhα proteins in produced in serotonergic neurons mediate axonal repulsion, and this repulsive force counterbalances target derived guidance cues to define the diffuse distribution pattern of serotonergic axons, which is required for normal affective function The specific aims of this study are designed to rigorously test the validity of this working model and to further understand the underlying cellular and molecular mechanisms. In Aim 1, we will distinguish the roles of serotonergic neurons and target fields in serotonergic circuit formation, and determine the nature of the serotonergic wiring alterations. In Aim 2, we will investigate whether molecular diversity of Pcdhα proteins plays a role in this process, whether specific isoforms are required, and whether this role is Pcdhα-specific or replaceable by other Pcdh subclasses. In Aim 3, we will carry out single cell RNA-Seq to determine whether Pcdh isoform diversity exist in serotonergic neurons, and identify potential downstream targets mediating serotonergic axonal spacing by using Pcdhα deficient mice and appropriate controls. Knowledge gained from this study is expected to shed new light into circuitry mechanisms of depression and inspire novel therapeutics.

 描述（由申请人提供）：神经递质血清素是行为的基本调节剂，血清素缺乏导致许多使人衰弱的精神疾病，包括抑郁症。神经系统中的多巴胺能神经元数量相对较少，但它们调节大量神经元的活动。为了实现这一点，多巴胺能神经元发出长距离的轴突投射，这些轴突投射在大脑的几乎每一个区域都是树枝状的，并精心制作了一个扩展的神经网络。然而，神经元能回路形成的分子和细胞机制在很大程度上是未知的。最近的研究表明，原钙粘蛋白（Protocadherin，Pcdh）α基因簇在这一过程中起着重要作用。哺乳动物的三个Pcdh基因簇（α、β、γ）编码一个大家族的嗜同性细胞表面蛋白，其在单个神经元中以随机组合随机表达。遗传学研究表明，Pcdhα蛋白以类似于果蝇Dscam 1蛋白的方式介导树突排斥和自我回避。我们产生了Pcdhα簇缺失小鼠，发现它们表现出抑郁样行为以及紊乱的多巴胺能投射，最突出的是在介导情绪处理的边缘系统结构中。在Pcdhα缺失的情况下，多巴胺能静脉曲张的空间分布是随机的，这可能是由于多巴胺能轴突之间的排斥力丧失。此外，Pcdhα突变体中的多巴胺能轴突在大脑的某些区域高度富集，而在其他区域则被耗尽，这表明还涉及指导机制。值得注意的是，Pcdhα基因在多巴胺能神经元中的条件性缺失重现了多巴胺能神经元的布线表型以及抑郁样行为。相反，当缺失被限制在目标区域时，多巴胺能神经元的连接和情感功能是不变的。基于这些观察结果，提出了一种多巴胺能轴突分支的工作模型，其中在多巴胺能神经元中产生的Pcdhα蛋白介导轴突排斥，并且这种排斥力抵消了靶源导向线索以定义多巴胺能轴突的弥漫分布模式，本研究的具体目的是严格测试这个工作模型的有效性，进一步了解潜在的细胞和分子机制。在目标1中，我们将区分的作用，肾上腺素能神经元和靶领域的肾上腺素能电路的形成，并确定的肾上腺素能布线改变的性质。在目标2中，我们将研究Pcdhα蛋白的分子多样性是否在这一过程中发挥作用，是否需要特定的同种型，以及这种作用是否是Pcdhα特异性的或可被其他Pcdh亚类取代。在目标3中，我们将使用Pcdhα缺陷小鼠和适当的对照进行单细胞RNA-Seq，以确定Pcdh亚型多样性是否存在于多巴胺能神经元中，并确定介导多巴胺能轴突间距的潜在下游靶点。从这项研究中获得的知识有望为抑郁症的电路机制提供新的线索，并激发新的治疗方法。