Functional Genetics of the Neuronal Sodium Channel Gene SCN8A

摘要 SCN8A基因编码电压门控钠通道Nav1.6，其在整个神经元中表达。 中枢和外周神经系统。Nav1.6主要集中在轴突起始段和轴突节 兰维尔SCN8A的突变影响大脑和外周神经功能的许多方面。2012年我们 描述了一名儿童早期癫痫性脑病的SCN8A第一次突变。此后，更多 在这种严重形式的癫痫中已经鉴定了超过150种从头错义突变（OMIM # 614558）。 我们对10例患者突变的功能表征表明，功能获得性突变导致 通道过度活跃是导致SCN8A脑病的主要致病机制。我们 产生了第一个鉴定的SCN8A突变p.Asn1768Asp的小鼠模型，该突变被广泛用于 评估治疗干预措施。我们将用这个模型来分离一种最近发现的基因修饰剂 从而彻底挽救癫痫发作和猝死。我们还将评估临床前 反义寡核苷酸和RNAi试剂抑制显性基因表达的有效性 N1768D小鼠模型中的SCN 8A突变。目的探讨重度肌张力减退与 许多SCN8A突变，我们已经产生了一个新的条件性小鼠模型与CRE依赖性表达 更严重的病人突变p.Arg1872Trp我们将使用这个新模型来研究突变体的作用 Nav1.6在不同发育阶段的特定神经元亚群中的表达。这个条件模型也将是 用于直接测试心脏过度活跃的Nav1.6表达对猝死风险的贡献。 这些研究将为SCN8A的致病机制提供新的知识 并将测试基因抑制作为治疗干预的有效性 严重的神经紊乱

Abstract The SCN8A gene encodes the voltage-gated sodium channel Nav1.6 that is expressed in neurons throughout the central and peripheral nervous system. Nav1.6 is concentrated at the axon initial segment and nodes of Ranvier. Mutations of SCN8A affect many aspects of brain and peripheral nerve function. In 2012 we described the first mutation of SCN8A in a child with early onset epileptic encephalopathy. Since then more than 150 de novo missense mutations have been identified in this severe form of epilepsy (OMIM # 614558). Our functional characterization of 10 patient mutations demonstrated that gain-of-function mutations resulting in channel hyperactivity are the major pathogenic mechanism underlying SCN8A encephalopathy. We generated a mouse model of the first identified SCN8A mutation, p.Asn1768Asp, that is widely used for evaluation of therapeutic interventions. We will use this model to isolate a recently discovered genetic modifier that results in complete rescue of seizures and sudden death. We will also assess the pre-clinical effectiveness of antisense oligonucleotides and RNAi reagents that suppress the expression of the dominant SCN8A mutation in the N1768D mouse model. To explore the basis for the severe hypotonia associated with many SCN8A mutations, we have generated a new conditional mouse model with CRE-dependent expression of the more severe patient mutation p.Arg1872Trp. We will use this new model to examine the role of mutant Nav1.6 in specific subsets of neurons at varying stages of development. This conditional model will also be used to directly test the contribution of cardiac expression of hyperactive Nav1.6 to the risk of sudden death. These studies will provide new knowledge regarding pathogenic mechanisms underlying SCN8A encephalopathy, and will test the effectiveness of gene suppression as a therapeutic intervention for this severe neurological disorder.