Mechanisms of Calcium Transients in Neuronal Development

描述（由申请人提供）：在先前的工作中，我们发现了胚胎非洲爪蟾脊髓神经元中细胞内钙（Ca）的三类自发瞬时升高，并表明它们具有不同的功能，在突触形成之前以频率依赖性方式调节分化方面：1）Ca尖峰由发育瞬时Ca依赖性动作电位产生，并调节神经递质的表达。2)生长锥Ca瞬变在生长锥中局部产生并调节轴突延伸的速率。3)丝状伪足钙瞬变产生于丝状伪足的尖端，并调节生长锥的转动。拟议的研究有三个具体的目标，解决这些胚胎脊髓神经元分化的钙瞬变的作用机制。第一个目的是研究钙峰调节神经递质表达的机制。第二个目的是分析产生导致钙尖峰的开始和终止的膜电位变化的机制。第三个目标是研究电压门控钙通道调节生长锥功能的机制。我们描述的实验，以解决以下问题：什么样的分子参与行动的钙尖峰？是什么机制导致膜电位的变化，导致钙峰期的开始和终止？生长锥电压门控钙通道的作用机制是否涉及与细胞外基质分子的相互作用或机械增强的递质释放？本研究的直接目标是验证关于脊椎动物脊髓神经元分化早期钙瞬变机制的假设。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.