Functional Consequences of Developmental Myosin II Down-regulation in Neurons

描述(申请人提供)：发育中的神经元经历复杂的基因表达变化，转化为神经元功能的机械性差异。由于技术问题，大多数研究旨在了解轴突延伸的机制，因为它们与再生尝试有关，是基于对早期胚胎神经元的研究。在这项拟议的研究中，我讨论了当背根神经节感觉神经元从早期发育阶段过渡到晚期发育阶段时，轴突延伸机制发生变化的细胞骨架基础。机械酶肌球蛋白II被认为是早期胚胎轴突伸展和引导机制的主要组成部分。我们的初步数据表明，肌球蛋白II在晚期感觉神经元中下调，晚期神经元利用一种不依赖于机械酶肌球蛋白II功能的轴突延伸机制来延长轴突。此外，与早期神经元不同，晚期神经元在肌球蛋白II依赖的分析中不能接受指导。这项研究的主要目的是确定是否可以通过实验重新表达肌球蛋白II来恢复晚期神经元的轴突延伸机制。这些研究的结果将确定在晚期神经元中重新表达肌球蛋白II是否有可能逆转轴突延伸和引导机制，使之恢复到早期胚胎神经元所利用的机制。神经系统损伤的康复是一个主要的社会问题，特别是对暴力行为发生率较高的人群影响更大。这些研究的长期目标是通过确定轴突延伸机制在发育过程中如何变化，以及这些变化是否可以逆转以产生具有更高再生潜力的神经元，从而提供与促进损伤个体轴突再生相关的信息。越来越多的证据表明，轴突的伸展和引导机制是发育调节的。在这项提议中，我试图 阐明发育过程中肌球蛋白II表达下调的功能后果 并确定是否可以通过肌球蛋白II的重新表达来使较老的神经元“恢复活力”。

DESCRIPTION (provided by applicant): Developing neurons undergo complex changes in gene expression that translate into mechanistic differences in how the neuron functions. The majority of studies aimed at understanding the mechanisms of axon extension, as they relate to regenerative attempts, are based on studies of early embryonic neurons due to technical issues. In the proposed research I address the cytoskeletal basis of changes that occur in the mechanism of axon extension as dorsal root ganglion sensory neurons transition from early to late developmental stages. The mechano-enzyme myosin II has been determined to be a major component of the mechanism of axon extension and guidance of early embryonic axons. Our preliminary data demonstrate that myosin II is down- regulated in late stage sensory neurons, and that late stage neurons utilize a mechanism of axon extension independent on the function of the mechano-enzyme myosin II for axon extension. In addition, late stage neurons fail to undergo guidance in myosin II-dependent assays, unlike early stage neurons. The major aim of the research proposed is to determine if the mechanism of axon extension in late stage neurons can be "rejuvenated" by experimental re-expression of myosin II. The results of these studies will determine whether re-expression of myosin II in late stage neurons has the potential to revert the mechanisms of axon extension and guidance to those utilized by early embryonic neurons. Recovery from Injury to the nervous system is a major societal issue, particularly affecting populations with higher incidence of violent behavior. The long term goal of these studies is to provide information relevant to the promotion of axon regeneration in injured individuals by determining how the mechanism of axon extension changes during development and whether these changes can be reverted to generate neurons with increased regenerative potential. Mounting evidence indicates that the mechanisms of axon extension and guidance are developmentally regulated. In this proposal I seek to elucidate the functional consequences of the developmental downregulation of myosin II expression in sensory neurons and determine if older neurons can be "rejuvenated" by re-expression of myosin II.