MUTATIONS IN CALCIUM CHANNELS CAUSING VERTIGO AND ATAXIA

本提案中概述的实验旨在研究 CACNL 1A 4中的突变，其编码脑钙通道亚基， 导致家族性偏瘫患者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）和脊髓小脑性共济失调 共济失调6型（SCA 6）。 分子遗传学技术的进步导致了 在许多神经退行性疾病中负责的突变基因。 然而，疾病的生理基础往往仍然不清楚，因为 突变基因产物的功能尚不清楚。 随着近期 鉴定涉及脑钙的CACNL 1A 4突变 通道已知是重要的神经元功能，三个等位基因 包括FHM、EA-2和SCA 6在内的疾病提供了一个模型来阐明 基因型-表型关系 分子技术将用于筛选30多个基因的突变， 在我们的数据库中出现症状的无关患者可能 由CACNL 1A 4突变引起。 新的点突变已经 在这些家族中的两个中被确定，而小CAG重复 在其他三个家庭中发现了扩张。 定点 诱变与膜片钳电生理技术相结合， 应用于研究异源的功能后果 表达突变的钙通道亚基。 增加或改变- 功能、单倍不足、显性负效应和神经毒性 所有这些效应都是针对CACNL 1A 4突变提出的。 电生理和生物化学技术将用于解决 这些不同的可能机制。 治疗反应的基础 乙酰唑胺也将进行研究。 阐明表型遗传的分子生理基础 异质性不仅将大大有助于我们 了解一种对大脑功能很重要的蛋白质， 有助于发展理性治疗。 这项工作的进一步相关性， 强调了更常见的基底动脉型偏头痛和梅尼埃综合征 眩晕和共济失调的重叠症状， 我们打算研究的病人

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.