NEUROMUSCULAR DISEASE GENE ENCODING A NEW SODIUM CHANNEL

我们最近分离出一个新的基因，SCN 8A，它是一个成员， 哺乳动物电压门控钠通道α亚单位基因家族。我们 证明了小鼠神经系统突变的MED（“运动终板 疾病）与SCN 8A中的突变相关。灭活小鼠 Scn 8a的突变具有神经肌肉疾病，其特征在于 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。scn 8a转录本存在 在脑和脊髓，符合临床综合征。 从医学小鼠外推，我们预测人类的无效等位基因 SCN 8A将是致命的，而部分活性等位基因将与 症状包括肌肉无力和小脑共济失调我们有 绘制了人类SCN 8A基因的图谱，并确定了用于连锁分析的标记。 为了鉴定具有SCN 8A缺陷的人类患者的突变，我们 将克隆和测序人类cDNA，并确定内含子/外显子 人类基因的边界将分析适当患者的DNA 通过SSCP，化学错配和其他突变检测技术。我们 将决定三种自发突变的分子基础 包括震动，一个有轻微小脑共济失调的等位基因。突变 在受影响的个体中鉴定的人类和小鼠Scn 8a将被 以允许分析它们的 药理学和电生理学特性。的作用 Scn 8a的选择性剪接产物将用 发展和功能研究。人类和老鼠的基因序列 将比较SCN 8A启动子以鉴定保守的调控基因。 元素还将在转基因小鼠中测定启动子功能。这 这项工作将提供正常和突变形式的彻底表征， 一种新的钠通道，有助于诊断和治疗 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.