NEUROMUSCULAR DISEASE GENE ENCODING A NEW SODIUM CHANNEL

我们最近分离到一个新的基因，SCN8A，它是 哺乳动物电压门控钠通道α亚单位基因家族。我们 证明了小鼠神经突变体MED(‘运动终板) 疾病)与SCN8A的突变有关。失活的小鼠 Scn8a突变具有神经肌肉疾病，其特征是 神经肌肉传递，导致瘫痪和肌肉萎缩，以及 小脑浦肯野细胞变性。Scn8a记录在案 在脑和脊髓，与临床症状一致。 从医学小鼠推断，我们预测人类的零等位基因 SCN8A将是致命的，而部分活跃的等位基因将被关联 症状包括肌肉无力和小脑性共济失调。我们有 定位了人的SCN8A基因，并确定了用于连锁分析的标记。 为了鉴定存在SCN8A缺陷的人类患者的突变，我们 将克隆和测序人类基因并鉴定内含子/外显子 人类基因的边界。将对适当患者的DNA进行分析 通过SSCP、化学错配等突变检测技术。我们 将确定三个自发的MED突变的分子基础 包括Jolting，一种患有轻度小脑性共济失调的可行等位基因。突变 在受影响的个体中发现的人和鼠的Scn8a将是 合并到表达式构造中，以允许分析其 药理和电生理特性。的作用 或者，Scn8a的剪接产品将通过以下方式进行评估 发育和机能研究。人类和老鼠的序列 SCN8A启动子将进行比较，以确定保守的监管 元素。还将在转基因小鼠中检测启动子的功能。这 这项工作将提供对正常和突变形式的 一种新的钠通道，并有助于诊断和治疗高血压 神经肌肉疾病。

We recently isolated a novel gene, SCN8A, that is a member of the mammalian voltage gated sodium channel alpha subunit gene family. We demonstrated that the mouse neurological mutant med ('motor endplate disease') is associated with mutations in SCN8A. Mice with inactivating mutations of Scn8a have neuromuscular disease characterized by failure of neuromuscular transmission, leading to paralysis and muscle atrophy, and degeneration of cerebellar Purkinje cells. Scn8a transcripts are present in brain and spinal cord, consistent with the clinical syndrome. Extrapolating from the med mouse, we predict that null alleles of human SCN8A would be lethal, while partially active alleles would be associated with syndromes that include muscle weakness and cerebellar ataxia. We have mapped the human SCN8A gene and identified markers for linkage analysis. In order to identify mutations in human patients with defects in SCN8A, we will clone and sequence the human cDNA and identify the intron/exon borders of the human gene. DNA from appropriate patients will be analyzed by SSCP, chemical mismatch, and other mutation detection techniques. We will determine the molecular basis for the three spontaneous med mutations including jolting, a viable allele with mild cerebellar ataxia. Mutations of human and mouse Scn8a identified in affected individuals will be incorporated into an expression construct to permit analysis of their pharmacological and electrophysiological properties. The role of alternatively spliced products of Scn8a will be evaluated with developmental and functional studies. The sequences of the human and mouse SCN8A promoters will be compared to identify conserved regulatory elements. Promoter function will also be assayed in transgenic mice. This work will provide thorough characterization of normal and mutated forms of a novel sodium channel and contribute to the diagnosis and treatment of neuromuscular disease.