Mechanisms of Calcium Transients in Neuronal Development

描述(申请人提供)：在以前的工作中，我们在非洲爪哇胚胎脊髓神经元中发现了三种类型的自发瞬时细胞内钙(Ca)升高，并表明它们具有不同的功能，在突触形成之前以一种频率依赖的方式调节分化的各个方面：1)钙尖峰由发育的瞬时钙依赖动作电位产生，并调节神经递质的表达。2)生长锥内局部产生生长锥钙瞬变，调节轴突伸展速度。3)丝状突起尖端产生丝状突起，调节生长锥体的转动。这项拟议的研究有三个具体目标，旨在解决钙瞬变在这些胚胎脊髓神经元分化中的作用机制。第一个目的是研究钙尖峰信号调节神经递质表达的机制。第二个目的是分析引起膜电位变化的机制，这些变化导致钙尖峰的开始和终止。第三个目的是研究电压门控性钙通道调节生长锥功能的机制。我们描述了解决以下问题的实验：哪些分子参与了钙尖峰的作用？是什么机制引起了膜电位的变化，从而导致了钙尖峰时期的开始和结束？生长激素电压门控钙通道的作用机制是与细胞外基质分子相互作用还是机械促进递质释放？这项研究的直接目标是测试关于脊椎动物脊髓神经元分化早期阶段钙瞬变机制的假说。长期目标是提供有关控制发育过程的细胞和分子机制的信息，这将有助于理解神经系统的发育障碍。

DESCRIPTION (provided by applicant): In previous work we discovered three classes of spontaneous transient elevations of intracellular calcium (Ca) in embryonic Xenopus spinal neurons and showed that they have distinct functions, regulating aspects of differentiation in a frequency-dependent manner prior to synapse formation: 1) Ca spikes are generated by developmental transient Ca-dependent action potentials and regulate expression of neurotransmitters. 2) Growth cone Ca transients are generated locally in the growth cone and regulate the rate of axon extension. 3) Filopodial Ca transients are produced at the tips of filopodia and regulate growth cone turning. The proposed research has three specific aims that address the mechanisms of action of Ca transients in differentiation of these embryonic spinal neurons. The first aim investigates the mechanisms by which Ca spikes regulate neurotransmitter expression. The second aim analyzes the mechanism generating changes in membrane potential that lead to onset and termination of Ca spiking. The third aim investigates the mechanism by which voltage-gated Ca channels regulate growth cone function. We describe experiments to address the following questions: What molecules are involved in the action of Ca spikes? What mechanisms generate the changes in membrane potential that lead to onset and termination of the period of Ca spiking? Does the mechanism of action of growth cone voltage-gated Ca channels involve interaction with extracellular matrix molecules or mechanically enhanced transmitter release? The immediate goal of this research is to test hypotheses about the mechanisms of Ca transients in the early stages of differentiation of vertebrate spinal neurons. The long term goal is to provide information about the cellular and molecular machinery that governs processes of development, which will contribute to understanding developmental disorders of the nervous system.