Molecular Physiology of Myotonia and Periodic Paralysis

肌强直和周期性麻痹的分子生理学

基本信息

批准号：
9108578
负责人：
STEPHEN C. CANNON
金额：
$ 28.64万
依托单位：
UNIVERSITY OF CALIFORNIA LOS ANGELES
依托单位国家：
美国
项目类别：
财政年份：
1994
资助国家：
美国
起止时间：
1994-03-10 至 2019-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9108578
关键词：
Accounting Action Potentials Adult Affect Animals Arginine Arrhythmia Behavior Biological Models Clinical Computers Defect Dependence Depressed mood Disease Electrodes Environment Epilepsy Fiber Frequencies Functional disorder Funding Gated Ion Channel Genes Genetically Engineered Mouse Goals Health Human Hyperkalemic periodic paralysis Hypokalemia Hypokalemic periodic paralysis In Vitro Individual Knock-in Mouse Knowledge Lead Learning Link Measures Migraine Missense Mutation Modeling Molecular Mus Muscle Muscle Contraction Mutation Myopathy Myotonia Neuromuscular Diseases Optical Methods Paralysed Pathway interactions Phenotype Physiology Pilot Projects Point Mutation Predisposition Property Protons Research Design Skeletal Muscle Sodium Channel Stimulus Structure Symptoms System Testing Therapeutic Tubular formation Variant Voltage-Clamp Technics Work base clinical phenotype comparative design disease phenotype gain of function mutation improved insight loss of function mouse model mutant novel strategies response sensor voltage

项目摘要

DESCRIPTION (provided by applicant): The myotonias and periodic paralyses are heritable diseases of skeletal muscle in which mutations of voltage-gated ion channels alter the electrical excitability of the fiber. The long-term goals of this project are to characterize the functional defects of mutant channels in these disorders and to determine how abnormal channel behavior produces symptoms in affected individuals. In these disorders, muscle dysfunction is caused by intermittent derangements in the electrical excitability of the fiber, which may be pathologically enhanced or depressed. Myotonia is a disorder of enhanced excitability wherein a single stimulus elicits a high- frequency burst of action potentials that produces involuntary persistent muscle contraction lasting seconds. Conversely, periodic paralysis results from a depolarization -induced loss of muscle excitability. Missense mutations in the adult skeletal muscle sodium channel (NaV1.4) may cause myotonia, periodic paralysis, or a combination of both in the same individual. The pathophysiological basis for this variation in clinical phenotype, all arising from mutations in a common sodium channel gene is a major focus of the studies in this proposal. Our experimental approach is to identify alterations in the behavior of mutant channels by measuring ionic current, and then use computer or animal-based models to explore how specific alterations in channel function give rise to myotonia or periodic paralysis. Aim 1 is to characterize the gating behavior of NaV1.4 channels, with a new focus on characterizing these properties for channels expressed in their native skeletal muscle environment. The availability of two mouse lines generated in our lab with knock-in point mutations in NaV1.4 (M1592V and R669H) offers a unique opportunity to characterize mutant channel behavior as occurs in muscle. Our studies on gating of disease- associated mutations of NaV1.4 will also explore the exciting new finding that missense mutations of arginines within S4 voltage-sensor domains may give rise to gating pore currents through an alternative permeation pathway different from the central pore. The propagation of action potentials into the transverse tubular system (TTS) and the activity-dependent accumulation of K+ therein are critical determinants of susceptibility to myotonia. Aim 2 will provide greater understanding for this important feature of muscle excitability by using state-of-the-art optical methods to measure TTS voltage transients and analytical models to estimate K+ accumulation both in normal mammalian muscle and for mouse models of myotonia and periodic paralysis. Aim 3 is a comparative analysis of the clinical phenotypes and electrophysiological properties of muscle from mice harboring either the M1592V or R669H mutations, as a model for gaining further insight on the mechanistic basis for the divergent phenotypes observed in humans for these allelic disorders of NaV1.4 (hyperkalemic periodic paralysis with myotonia contrasted by hypokalemic periodic paralysis without myotonia).

描述（由申请人提供）：肌瘤和周期性瘫痪是骨骼肌的遗传疾病，其中电压门控离子通道的突变改变了纤维的电兴奋性。该项目的长期目标是表征这些疾病中突变通道的功能缺陷，并确定异常的通道行为如何在受影响的个体中产生症状。在这些疾病中，肌肉功能障碍是由纤维的电兴奋性间歇性扰动引起的，纤维的电兴奋性可能会在病理上增强或抑郁。 Myotonia是一种增强兴奋性的疾病，其中单个刺激引起了高频爆发的动作电位，产生了持续几秒钟的非自愿持续肌肉收缩。相反，周期性麻痹是由于去极化引起的肌肉兴奋性丧失而引起的。成人骨骼肌钠通道（NAV1.4）中的错义突变可能会导致肌瘤，周期性麻痹或两者在同一个体中的组合。这种临床表型差异的病理生理基础，所有由公共钠通道基因中突变引起的都是该提案研究的主要重点。我们的实验方法是通过测量离子电流来确定突变通道行为的改变，然后使用计算机或基于动物的模型来探索通道功能的特定变化如何导致肌张力或周期性瘫痪。 AIM 1是表征NAV1.4通道的门控行为，其新的重点是表征这些在其天然骨骼肌肉环境中表达的通道的特性。在我们的实验室中生成的两种小鼠线的可用性，其中NAV1.4（M1592V和R669H）中的敲点突变为表征突变通道行为的独特机会。我们对NAV1.4相关突变的门控的研究还将探讨令人兴奋的新发现，即S4电压传感器结构域中精氨酸的错义突变可能会通过与中央孔不同的替代渗透途径引起门控孔电流。动作电位传播到横向管状系统（TTS）和其中K+的活性依赖性积累中的传播是对Myotonia易感性的关键决定因素。 AIM 2将通过使用最先进的光学方法来测量TTS电压瞬变和分析模型，以估算正常哺乳动物肌肉中的K+积累，并为Myotonia的小鼠模型和周期性麻痹提供更深入的了解肌肉兴奋性的这一重要特征。。 AIM 3是对带有M1592V或R669H突变的小鼠的临床表型和电生理特性的比较分析，这是一种模型，以进一步了解这些NAV1等位基因疾病的人类在人类中观察到的发散表型的机械基础。 4（高钾血症周期性瘫痪与肌瘤的瘫痪与降低性周期性瘫痪形成对比）。