Functional Genetics of the Neuronal Sodium Channel Gene SCN8A

描述(申请人提供)：电压门控钠通道SCN8A在CMS和PNS的神经元中表达，亚细胞定位于轴突起始段、树突和Ranvier结节。这种广泛的表达模式表明，SCN8A的突变可能会影响大脑和周围神经功能的许多方面。在之前的资助期间，我们在体内产生了Cre/loxP靶向条件性失活的‘FLOXED’小鼠等位基因。我们还在一个认知缺陷的家庭中发现了第一个报道的人类SCN8A突变。我们将使用Floted小鼠模型来研究Scnda缺乏对小鼠认知的影响。我们鉴定了SCN8A的5‘非编码外显子和启动子，它们位于第一个编码外显子的上游70kb。SCN8A的5‘非编码外显子包含三个在鱼类、鸡和哺乳动物中进化保守的非编码元件。我们将鉴定与这些位点有亲和力的转录调节蛋白。我们将扩展我们对人类SCN8A突变及其在运动障碍和认知功能障碍中的作用的分析。我们将研究我们在一个新的ENU诱导的小鼠突变中发现的SCN8A N-末端区域的一个新的错义突变的分子机制。为了阐明N末端的作用，我们将研究该突变对运输、蛋白质相互作用和通道活性的影响。总体而言，这项建议将继续一个长期的、富有成效的计划，旨在了解必要的钠通道SCN8A在正常功能和疾病中的作用。公共卫生相关性：神经疾病和精神疾病之间存在着生物学上的连续体。参与神经元信号传递的通道突变会影响这两种功能。该项目将利用人类突变的小鼠模型，表征钠通道基因特定变化对神经和行为的影响。

DESCRIPTION (provided by applicant): The voltage-gated sodium channel SCN8A is expressed in neurons throughout the CMS and PNS, with subcellular localization in axonal initial segments, dendrites, and nodes of Ranvier. The widespread expression pattern suggests that mutations of SCN8A could affect many aspects of brain and peripheral nerve function. During the previous funding period, we generated a 'floxed' mouse allele for CRE/loxP targeted conditional inactivation in vivo. We also found the first reported mutation of human SCN8A in a family with cognitive deficits. We will use the floxed mouse model to investigate the effects of Scnda deficiency on cognition in the mouse. We have characterized the 5' noncoding exons and promoter of SCN8A which are located 70 kb upstream of the first coding exon. The 5' noncoding exon of SCN8A contains three noncoding elements that are evolutionary conserved in fish, chicken and mammals. We will identify transcriptional regulatory proteins with affinity for these sites. We will extend our analysis of human mutations of SCN8A and their role in movement disorders and cognitive dysfunction. We will investigate the molecular mechanism of a novel missense mutation in the N-terminal domain of SCN8A that we identified in a novel ENU induced mouse mutant. The effect of this mutation on trafficking, protein interaction, and channel activity will be investigated, in order to elucidate the role of the N-terminus. Overall, this proposal will continue a long-term, productive program directed towards understanding the roles of the essential sodium channel SCN8A in normal function and disease. Public health relevance: There is a biological continuum between neurological disease and the psychiatric disorders. Mutations in channels involved in neuronal signalling can affect both types of functions. This project will characterize the neurological and behavioral effects of specific changes in sodium channel genes, using mouse models of human mutations.