Molecular Mechanisms Controlling Somatosensory Neuron Development

控制体感神经元发育的分子机制

• 批准号: 8854779
• 负责人: Michael Fleming
• 金额: $ 4.22万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2016-05-16
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8854779
• 关键词: Afferent Neurons; Antibodies; Axon; Binding; Binding Sites; Bioinformatics; Biological Assay; Biological Models; Caliber; Cell Communication; Characteristics; Charcot-Marie-Tooth Disease; Communication; Complex; Cysteine; Data; Development; Disease; Down-Regulation; EGF gene; Electrons; Extracellular Domain; Family member; Fiber; Fingers; Genetic Programming; Genetic Transcription; Goals; Health; Human; Injection of therapeutic agent; Knockout Mice; Location; Luciferases; Mediator of activation protein; Meissners Corpuscle; Microscopy; Molecular; Molecular Genetics; Motor; Mus; Muscle Cells; Muscle Fibers; Muscle Spindles; Mutant Strains Mice; Myelin; Myelin Sheath; Natural regeneration; Nature; Neonatal; Neuregulin 1; Neuromuscular Junction; Neurons; Organ; Pacinian Corpuscles; Peripheral; Peripheral Nerves; Peripheral Nervous System; Peripheral Nervous System Diseases; Primates; Protein Isoforms; Recombinants; Regulation; Reverse Transcriptase Polymerase Chain Reaction; Role; Schwann Cells; Sensory; Signal Transduction; Thick; Transcript; Work; chromatin immunoprecipitation; foot; improved; in vivo; mutant; myelination; neuron development; promoter; public health relevance; receptor; relating to nervous system; research study; somatosensory; tool; transcription factor

DESCRIPTION (provided by applicant): Neuron-Schwann cell interactions are important for the development, function, and regeneration of the peripheral nervous system (PNS). Perturbations in this crosstalk can cause debilitating diseases, such as Charcot- Marie-Tooth disease and other peripheral neuropathies. However, the molecular nature of the interactions between axons and different classes of Schwann cells and the regulation of these interactions are not fully understood. In this proposal, I will determine how the transcription factor Er81 controls development of Pacinian corpuscles, which are specialized sensory end organs composed of a single myelinated sensory axon and non-myelinating corpuscle-forming Schwann cells. Er81 mutant mice have no Pacinian corpuscles, and my preliminary data suggest that the primary deficit comes from disrupted axon-Schwann cell interactions. Since Er81 is a transcription factor, this effect must be executed by other downstream effectors. Neuregulin-1 (Nrg1) is a key mediator of axon-Schwann cell interactions. The expression level of an isoform of Nrg1 with cysteine rich extracellular domain (Nrg1-CRD) determines the thickness of myelination of peripheral axons. In addition, the development of muscle spindles, which contain sensory axons, muscle fibers, and non-myelinating Schwann cells, requires other Nrg1 isoforms, most likely those with an Ig-like extracellular domain (Nrg1-Ig). Despite the important functions of Nrg1, how Nrg1 is regulated to acquire an appropriate expression level is completely unknown. Interestingly, I found that Er81 mutant mice display decreased expression of both isoforms of Nrg1 in somatosensory neurons and reduced myelination thickness of peripheral axons. Therefore, I hypothesize that Er81 regulates the expression of multiple isoforms of Nrg1 to control axonal interactions with both myelinating and non-myelinating Schwann cells. In Aim 1, I will determine that Er81 is required in neurons to maintain a high level of myelination of large-diameter somatosensory axons. I will quantify the extent of the downregulation of Nrg1-CRD and Nrg1-Ig in Er81 mutant somatosensory neurons, and demonstrate that Er81 regulates Nrg1 expression by direct binding to the Nrg1 promoter. To place Nrg1 downstream of Er81 in Pacinian corpuscle development, I will rescue Pacinian corpuscles in Er81 mutant mice by ectopically supplying Nrg1. In Aim 2, I will determine the role of Nrg1 in Pacinian corpuscle formation by ablating all isoforms of Nrg1 from somatosensory neurons. I will also determine which isoforms of Nrg1 are required for corpuscle formation through rescue experiments and analyzing isoform specific mutant mice. Lastly, I will examine if a high level of Nrg1 is sufficient to induce the formation of Pacinian corpuscles in an ectopic location, the mouse foot pad. Collectively, anticipated results from my work will identify the firs transcriptional mechanism that controls the extent of myelination of PNS axons via the regulation of Nrg1, and elucidate molecular mechanisms of neuronal interaction with non-myelinating Schwann cells.

描述（由申请人提供）：神经元 - 雪旺细胞相互作用对于周围神经系统（PNS）的发展，功能和再生很重要。该串扰中的扰动会导致令人衰弱的疾病，例如charcot- marie-tooth疾病和其他周围神经病。但是，轴突与不同类别的雪旺细胞之间相互作用的分子性质以及这些相互作用的调节尚未完全了解。在此提案中，我将确定转录因子ER81如何控制Pacinian Copuscles的发展，Pacinian Copuscles是由单个髓鞘的感觉轴突和非层状体形体形的Schwann细胞组成的专业感觉末端器官。 ER81突变小鼠没有Pacinian小体，而我的初步数据表明，主要赤字来自破坏的轴突 - 切旺细胞相互作用。由于ER81是转录因子，因此必须由其他下游效应子执行此效果。 Neuregulin-1（NRG1）是轴突 - 切恩细胞相互作用的关键介体。 NRG1的同工型具有富含半胱氨酸的细胞外域（NRG1-CRD）的表达水平决定了周围轴突的髓鞘厚度。此外，肌肉纺锤体的发育含有感觉轴突，肌肉纤维和非层状雪旺氏细胞，需要其他NRG1同工型，最有可能具有Ig样细胞外域（NRG1-IG）的NRG1同工型。尽管NRG1具有重要的功能，但如何调节NRG1以获得适当的表达水平是完全未知的。有趣的是，我发现ER81突变小鼠在体感神经元中表现出NRG1的两种同工型的表达降低，并降低了外周轴突的髓鞘厚度。因此，我假设ER81调节了NRG1多种同工型的表达，以控制轴突相互作用与髓鞘和非层状Schwann细胞的表达。在AIM 1中，我将确定神经元中需要ER81来维持高直径的体感轴突的高度髓鞘。我将量化ER81突变体体感神经元中NRG1-CRD和NRG1-Ig的下调程度，并证明ER81通过直接结合NRG1启动子来调节NRG1的表达。要将ER81下游的NRG1放置在Pacinian Corpuscle开发中，我将通过异位提供NRG1来挽救ER81突变小鼠中的Pacinian Copuscles。在AIM 2中，我将通过从体感神经元中消除NRG1的所有同工型来确定NRG1在Pacinian Colduscle形成中的作用。我还将确定通过救援实验和分析同工型特异性突变小鼠需要哪些NRG1的同工型。最后，我将检查高水平的NRG1是否足以在异位位置鼠标脚垫中诱导Pacinian球体的形成。总的来说，我工作中的预期结果将确定通过调节NRG1控制PNS轴突骨髓程度的FIR转录机制，并阐明神经元相互作用与非层状Schwann细胞的分子机制。