Molecular Physiology of Myotonia and Periodic Paralysis

肌强直和周期性麻痹的分子生理学

• 批准号: 7820641
• 负责人: STEPHEN C. CANNON
• 金额: $ 49.91万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-28 至 2011-09-27
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7820641
• 关键词: Accounting; Action Potentials; Activities of Daily Living; Address; Adult; Affect; Age; American; Animal Model; Arginine; Arts; Behavior; Breeding; Calcium Channel; Capital; Carbonic Anhydrase Inhibitors; Charge; Chloride Channels; Computer Simulation; Critiques; Defect; Dependence; Development; Disease; Dose; Economics; Employment; Environment; Equilibrium; Equipment; Exposure to; Extravasation; Failure; Family; Fiber; Frequencies; Functional disorder; Funding; Gated Ion Channel; Gender; Gene Dosage; Generations; Genes; Genetically Engineered Mouse; Glucose; Goals; Grant; Human; Hypokalemia; Hypokalemic periodic paralysis; In Vitro; Individual; Inherited; Insulin; Intravenous infusion procedures; Investigation; Ions; Knock-in Mouse; Laboratories; Lead; Life Expectancy; Link; Measures; Membrane Potentials; Missense Mutation; Modeling; Molecular; Monovalent Cations; Morbidity - disease rate; Mus; Muscle; Muscle Contraction; Muscle Fibers; Mutant Strains Mice; Mutation; Myopathy; Myotonia; Optical Methods; Paralysed; Pathogenesis; Pathologic; Pathway interactions; Patients; Penetrance; Performance; Phenotype; Physiological; Physiology; Pilot Projects; Point Mutation; Positioning Attribute; Postdoctoral Fellow; Potassium Channel; Predisposition; Preparation; Productivity; Property; Protons; Recommendation; Recovery; Reporting; Role; Schools; Severities; Skeletal Muscle; Sodium Channel; Stimulus; Symptoms; System; Testing; Therapeutic Intervention; Tubular formation; United States National Institutes of Health; Work; base; clinical phenotype; depressed; gain of function mutation; graduate student; hyperkalemia; in vivo; interest; ionic balance; loss of function; mathematical model; meetings; mouse model; mutant; mutant mouse model; novel strategies; novel therapeutics; public health relevance; response; sensor; voltage; voltage clamp

DESCRIPTION (provided by applicant): This application is submitted in response to Notice Number NOT-OD-09-058: "NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications". The proposed studies expand the scope of the original application (R37-AR42703), by extending our studies on the pathomechanism of periodic paralysis to include Ca channel (CaV1.1) mutations responsible for hypokalemic periodic paralysis (HypoPP). The original application was focused exclusively on sodium channel (NaV1.4) defects in myotonia and periodic paralysis. The expanded studies in this competitive revision were not part of the original proposal. More specifically, the new proposed studies are not a line of investigation that failed to meet approval for recommendation of support by prior Scientific Review Group critique. HypoPP is the most common form of inherited periodic paralysis and is a significant cause of morbidity and lost productivity. We are excited to have successfully generated a knock-in CaV1.1 mutant mouse model of HypoPP, which in preliminary studies has a clear phenotype. This is the only animal model of HypoPP created to date and offers a unique opportunity to understand disease mechanism and to test therapeutic interventions. This project is not supported by any active grant to our laboratory, and support from NOT-OD-09-058 will be vital to continue to project in preparation for eventual submission of a new grant (R0-1). The proposed studies will comply with the economic objectives of the Recovery Act by creating 2.5 new positions of employment (postdoc, graduate student, technician) and adding new capital equipment to accelerate the pace of discovery on this project. PUBLIC HEALTH RELEVANCE: 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 the original project (AR42703) were to characterize the functional defects of mutant channels in these disorders and to determine how abnormal channel activity 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. Mutations of sodium channels (NaV1.4), chloride channels (ClC-1), K channels (Kir2.1), or Ca channels (CaV1.1) are established causes of myotonia and periodic paralysis in humans. The original project was focused exclusively on mutations in the adult skeletal muscle sodium channel (NaV1.4), to address the very interesting mechanistic question of how a point mutation in a single gene may cause myotonia, periodic paralysis, or a combination of both in the same individual. In this revised application, the scope of the project will be expanded to include an investigation of the mechanism by which mutations in the L-type Ca channel (CaV1.1) produce susceptibility to Hypokalemic Periodic Paralysis (HypoPP). The scientific approach is based on a combination of physiological studies in a knock-in mutant mouse model of CaV1.1-HypoPP, expression studies of disease-associated mutant channels, and mathematical modeling of muscle fiber excitability. Impact / Significance of the Revised Studies. While life-expectancy is normal for patients with periodic paralysis, it is a disabling condition that severely impacts performance at school or work, and interferes with activities of daily living. Tremendous advances have been gained in understanding the molecular defects associated with the periodic paralyses, as prototypical ion channelopathies [3, 11, 39]. The mechanistic link between altered channel function and loss of sarcolemmal excitability during an attack of weakness, however, is only partially understood for NaV1.4 mutations [2] and remains a complete mystery for CaV1.1 mutations in HypoPP. Heterologous expression studies have revealed biophysical defects of mutant CaV1.1 channels, but these changes do not readily provide an explanation for depolarization and paralysis. Moreover, the impact of these functional channel defects on sarcolemmal excitability has been difficult to ascertain experimentally, due to the scarcity of human HypoPP muscle suitable for study and the lack of any spontaneous animal model. Our genetically-engineered mouse model with a knock-in R528H mutation provides an outstanding opportunity to study the behavior of mutant CaV1.1 channels expressed in a muscle environment, to experimentally define the mechanism by which Vrest is aberrantly depolarized to cause weakness, and to explore the mode of action by which carbonic anhydrase inhibitors reduce the severity and frequency of attacks. In addition to elucidating disease pathogenesis, these studies may reveal new roles for CaV1.1 channels in maintaining Vrest and may provide a system for the rational development and testing of new therapeutic strategies to alleviate attacks of periodic paralysis. The proposed studies will comply with the economic objectives of the American Recovery and Reinvestment Act and the request for revised applications (NOT-OD-09-058) by creating 2.5 new positions of employment (postdoc, graduate student, technician) and adding new capital equipment to accelerate the pace of discovery on this project.

描述（由申请人提供）：此申请是为了响应通知号而提交的，NOT-OD-09-058：“ NIH宣布为竞争性修订申请提供恢复法案资金的可用性”。拟议的研究扩大了原始应用的范围（R37-AR42703），通过扩展我们对周期性麻痹的病理机理的研究，包括ca通道（CAV1.1）突变，负责低钾血症周期性瘫痪（HYPOPP）。最初的应用专门集中在肌酸和周期性瘫痪中的钠通道（NAV1.4）缺陷上。这项竞争性修订的扩大研究并不是原始提案的一部分。更具体地说，新提出的研究不是未能获得批准的调查范围，以提出先前的科学审查小组批评的支持。 HypOPP是遗传周期性瘫痪的最常见形式，是发病率和生产力降低的重要原因。我们很高兴成功地产生了HypOPP的敲入CAV1.1突变小鼠模型，该模型在初步研究中具有明确的表型。这是迄今为止创建的HYPOPP的唯一动物模型，并提供了一个独特的机会来了解疾病机制并测试治疗性干预措施。该项目不受我们实验室的任何积极赠款的支持，而NOT-OD-09-058的支持对于继续进行准备以准备最终提交新的赠款（R0-1）至关重要。拟议的研究将遵守《恢复法》的经济目标，通过创建2.5个新的就业立场（博士后，研究生，技术人员），并添加新的资本设备来加速该项目的发现速度。 公共卫生相关性：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。原始项目的长期目标（AR42703）是表征这些疾病中突变通道的功能缺陷，并确定异常通道活性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。钠通道（NAV1.4），氯化物通道（CLC-1），K通道（KIR2.1）或CA通道（CAV1.1）的突变是人类造成了肌育性的原因和周期性的瘫痪。最初的项目专门集中于成年骨骼肌钠通道（NAV1.4）的突变，以解决一个非常有趣的机械性问题，即单个基因中的点突变如何导致肌动症，周期性麻痹或同一个体中两者的组合。在此修订后的应用中，该项目的范围将扩大，包括对L型CA通道中突变（CAV1.1）中突变产生敏感性降低性瘫痪（HYPOPP）的机制的研究。科学方法基于在CAV1.1-HYPOPP的敲门突变体模型，疾病相关突变通道的表达研究以及肌肉纤维兴奋性的数学建模中的生理研究的组合。修订研究的影响 /意义。尽管对于周期性麻痹的患者而言，预期生命是正常的，但它是一种残疾状况，严重影响学校或工作的表现，并干扰日常生活的活动。在理解与周期性瘫痪有关的分子缺陷方面，已经获得了巨大的进步，作为原型离子通道病[3，11，39]。然而，在弱点攻击过程中，通道函数的改变与肌符号兴奋性的丧失之间的机械联系仅在NAV1.4突变[2]中被部分理解，并且仍然是CAV1.1 HYPOPP突变的完全谜。异源表达研究揭示了突变体CAV1.1通道的生物物理缺陷，但是这些变化并不能轻易为去极化和瘫痪提供解释。此外，由于适合研究和缺乏任何自发动物模型的人类肌肉肌肉的稀缺，这些功能通道缺陷对肌膜兴奋性的影响很难在实验上确定。我们具有敲入R528H突变的遗传工程小鼠模型为研究突变体CAV1.1在肌肉环境中表达的突变体的行为提供了一个绝佳的机会，以实验定义了VREST异常去极性以引起虚弱的机制，并探索了碳氧化酶抑制剂的行动方式，从而降低了碳氧化酶抑制剂的攻击性和次数。除了阐明疾病的发病机理外，这些研究还可能揭示了CAV1.1通道在维持VREST中的新作用，并可能为新的治疗策略的合理发展和测试提供了一种减轻周期性麻痹攻击的系统。拟议的研究将遵守《美国回收和再投资法》的经济目标以及修订的应用程序（非OD-09-058）的要求，通过创建2.5个新的就业立场（博士后，研究生，技术人员），并添加新的资本设备以加速该项目的发现速度。