K+ CHANNEL MODEL FOR TRINUCLEOTIDE-EXPANSION DISEASES

几种人类遗传性神经系统疾病是由扩展的 CAG重复，但病理生理机制仍不确定。 据报道，较长的CAG等位基因也在 双相情感障碍和精神分裂症患者，但缺陷 基因仍然未被识别。 我们分离出一个人类基因， 钙激活钾通道（hSKCa 3），发现于神经元和 含有新的CAG重复序列。 编码多聚谷氨酰胺重复序列， 氨基末端，该CAG重复序列在正常人中高度多态， 长等位基因在精神分裂症和双相情感障碍中过度表现。 我们现在建议联合收割机结合四个主要的优势 分子生物学，人类遗传学，神经解剖学， 生物化学和电生理学，以制定详细的生物物理 和药理学“指纹”。 使用嵌合的 hKCa 3与其“无重复”亲属hKCa 4之间的策略， 通过位点特异性诱变，我们将定义 这些蛋白质，并确定较长的聚谷氨酰胺的影响， 重复频道功能。 原位杂交技术研究 来自对照组和精神分裂症患者的大脑， hKCa 3神经元分布与神经递质的关系 受体和其他通道，并可能精确定位关键的解剖结构， 可能与精神分裂症有关的区域 通过定义 内含子/外显子组织，我们将能够启动 筛选研究，以确定hKCa 3中可能 与精神分裂症有关 我们还将确定 与其他精神分裂症的遗传标记相比。 hKCa 3天然启动子的鉴定将为 为了产生过表达hKCa 3的转基因小鼠， 多聚谷氨酰胺在大脑的相关区域重复;这样的小鼠 可能会表现出行为改变 这些实验提供了框架 为了了解多聚谷氨酰胺重复序列在蛋白质中的作用， 已知功能。 这些研究的长期目标是了解 hKCa 3在精神分裂症发病机制中的作用，并发展 该通道的特异性调节剂，其可能用于治疗 这种令人衰弱的神经精神紊乱

Several human hereditary neurological diseases are caused by expanded CAG repeats although the pathophysiological mechanism remains uncertain. Longer CAG alleles have also been reported to be over-represented in patients with bipolar disorder and schizophrenia, but the defective gene(s) remain unidentified. We isolated a human gene encoding a calcium-activated potassium channel (hSKCa3), found in neurons and containing a novel CAG repeat. Encoding a polyglutamine repeat near the amino terminus, this CAG repeat is highly polymorphic in normals, and long alleles are over-represented in schizophrenia and bipolar disorder. We now propose to combine the strengths of the four principal investigators in molecular biology, human genetics, neuroanatomy, biochemistry, and electrophysiology, to develop a detailed biophysical and pharmacological "fingerprint" of this channel. Using a chimeric strategy between hKCa3 and its "repeat-free" relative, hKCa4, coupled with site-specific mutagenesis, we will define functional domains within these proteins, and determine the effects of longer polyglutamine repeats on channel function. In-situ hybridization studies on human brains, from controls and patients with schizophrenia, will ascertain the neuronal distribution of hKCa3 in relation to neurotransmitter receptors and other channels, and potentially pinpoint key anatomical areas that might be implicated in schizophrenia. By defining the intron/exon organization of this gene, we will be able to initiate screening studies to identify point mutations in hKCa3 that might be associated with schizophrenia. We will also define the precise location of this gene with respect to other genetic markers for schizophrenia. The identification of the native promoter for hKCa3 will set the stage for the generation of transgenic mice that over-express hKCa3 with long polyglutamine repeats in the relevant regions of the brain; such mice might exhibit altered behavior. These experiments provide the framework for understanding the role of polyglutamine repeats in a protein of known function. The long term goal of these studies is to understand the role of hKCa3 in the pathogenesis of schizophrenia, and to develop specific modulators of this channel for potential use in the therapy of this debilitating neuropsychiatric disorder.