MUTATIONS IN CALCIUM CHANNELS CAUSING VERTIGO AND ATAXIA

这项提案中概述的实验试图研究如何 编码大脑钙通道亚单位的CACNL1A4发生突变， 家族性偏瘫患者出现发作性眩晕和共济失调症状 偏头痛(FHM)、发作性共济失调2型(EA-2)和脊髓小脑 共济失调6型(SCA6)。 分子遗传学技术的进步导致了对 在许多神经退行性疾病中负责任的突变基因。 然而，疾病的生理基础通常仍不清楚，因为 突变基因产物的功能尚不清楚。随着最近的 CACNL1A4基因突变与脑钙相关的鉴定 已知的在神经元功能中重要的通道，三个等位基因 包括FHM、EA-2和SCA6在内的疾病提供了一个模型来阐明 基因型-表型关系。 分子技术将被应用于筛选30多个基因突变 我们数据库中可能出现症状的无关患者 由CACNL1A4基因突变引起。新的点突变已经 在其中两个家族中被发现，而小CAG重复 在另外三个家系中发现了扩张。站点定向 突变结合膜片钳电生理技术将 被应用于研究异源函数的结果 表达突变的钙通道亚基。收益-或变化- 功能、单倍体功能不全、显性负效应和神经毒性 CACNL1A4的突变效应已被提出。 将使用电生理学和生化技术来解决 这些不同的可能机制。治疗反应的基础 对乙酰唑胺也将进行研究。 阐明表型的分子生理学基础 异质性不仅将极大地促进我们的 对一种对大脑功能很重要的蛋白质的理解 帮助开发合理的治疗方法。这项工作的进一步相关性是 更常见的基底性偏头痛和梅尼埃综合征 由眩晕和共济失调的重叠症状引起的 我们计划研究的患者。

The experiments outlined in this proposal seek to investigate how mutations in CACNL1A4, which encodes a brain calcium channel subunit, lead to symptoms of episodic vertigo and ataxia in familial hemiplegic migraine (FHM), episodic ataxia type 2 (EA-2), and spinocerebellar ataxia type 6 (SCA6). Advances in molecular genetic techniques have lead to the determination of responsible mutant genes in numerous neurodegenerative conditions. Yet, the physiologic basis of disease often remains unclear because the function of the mutant gene product is not known. With the recent identification of mutations in CACNL1A4 involving a brain calcium channel known to be important in neuronal function, the three allelic disorders including FHM, EA-2, and SCA6 provide a model to elucidate the genotype-phenotype relationship. Molecular techniques will be applied to screen for mutations in over 30 unrelated patients in our data base who present with symptoms possibly caused by mutations in CACNL1A4. Novel point mutations have already been identified in two of these families, while small CAG repeat expansions were found in three other families. Site-directed mutagenesis combined with patch clamp electrophysiologic techniques will be applied to study the functional consequences of heterologously expressed mutated calcium channel subunit. Gain- or change- of- function, haploinsufficiency, dominant negative effect, and neurotoxic effect have all been proposed for the mutations in CACNL1A4. Electrophysiologic and biochemical techniques will be used to address these different possible mechanisms. The basis of therapeutic response to acetazolamide will also be studied. Elucidating the molecular physiological basis of phenotypic heterogeneity not only will contribute substantially to our understanding of a protein important for brain function but also may help develop rational therapy. The further relevance of this work to the more common basilar migraine and Meniere's syndrome is emphasized by the overlapping symptoms of vertigo and ataxia in the group of patients that we propose to study.