K+ CHANNEL MODEL FOR TRINUCLEOTIDE-EXPANSION DISEASES

几种人类遗传性神经疾病是由扩张性 尽管CAG的病理生理机制尚不清楚，但CAG重复发生。 据报道，较长的CAG等位基因在 双相情感障碍和精神分裂症的患者，但有缺陷的 基因(S)仍未确定。我们分离了一种人类基因，编码一种 钙激活钾通道(HSKCa3)，发现于神经元和 含有一个新的CAG重复序列。编码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，并且 长等位基因在精神分裂症和双相情感障碍中被过度代表。 我们现在建议将四个原则的优点结合起来 分子生物学、人类遗传学、神经解剖学的研究人员， 生物化学和电生理学，以制定详细的生物物理 和这个通道的药理“指纹”。使用嵌合体 HKCa3和它的“无重复”亲缘hKCa4之间的策略耦合 通过定点突变，我们将在 这些蛋白质，并确定更长的聚谷氨酰胺的影响 在通道功能上重复。人的原位杂交研究 来自对照组和精神分裂症患者的大脑将确定 HKCa3的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学 可能与精神分裂症有牵连的区域。通过定义 这个基因的内含子/外显子的组织，我们将能够启动 筛选研究以确定hKCa3可能是 与精神分裂症有关。我们还将定义准确的位置 该基因与精神分裂症的其他遗传标记之间的关系。 HKCa3天然启动子的确定将为 用于生成过表达hKCa3和Long的转基因小鼠 多谷氨酰胺在大脑的相关区域重复；这样的小鼠 可能会表现出改变的行为。这些实验提供了一个框架 为了了解多谷氨酰胺重复序列在一种蛋白质中的作用 已知功能。这些研究的长期目标是了解 HKCa3在精神分裂症发病机制中的作用 这一通道的特异性调节剂可能用于治疗糖尿病 这种衰弱的神经精神障碍。

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.