The neuronal sodium channel gene SCN8A

SCN8A是一种丰富的电压门控钠通道，在哺乳动物的脑、脊髓和周围神经系统中都有表达。在之前的资助期间，我们在小鼠中发现了导致共济失调、肌张力障碍和进行性瘫痪的SCN8A突变，在GEFS+2型患者中发现了SCN1A突变。我们建议建立新的遗传模型，这将有助于理解神经元性钠通道的正常表达和致病潜力。SCN8A定位于有髓轴突和树突的Ranvier结节，以及中枢神经系统的突触前膜和突触后膜。我们将通过分析转基因小鼠中的表位标记嵌合通道来确定负责亚细胞定位的蛋白质结构域。我们将研究SCN8A基因的转录调控，包括启动子(S)和增强子元件的鉴定。我们将研究大脑中选择性剪接的区域分布，并测试RNA编辑的候选位置。我们将获得人类、小鼠和河豚的SCN8A基因的大规模基因组序列，并进行比较，以确定进化上保守的编码和非编码序列。我们将通过同源重组将loxP位点定位于SCN8A基因，从而产生特定神经元中SCN8A受调控的条件性失活的小鼠。为了制造人类多基因疾病的模型，我们将使SCN8A突变小鼠与携带功能相关蛋白零等位基因的小鼠杂交，如SCN2A和钠通道β亚基。这项工作将扩大我们对SCN8A在中枢和三叉神经节中的生理和细胞功能及其在神经系统疾病中的作用的认识。

SCN8A is an abundant voltage-gated sodium channel that is expressed throughout the mammalian brain, spinal cord and peripheral nervous system. During the previous funding period we identified mutations of SCN8A in the mouse that are responsible for ataxia, dystonia, and progressive paralysis, and mutations of SCN1A in patients with GEFS+ type 2. We propose to generate new genetic models that will contribute to understanding the normal expression and pathogenic potential of neuronal sodium channels. SCN8A is localized in the nodes of Ranvier in myelinated axons and in dendrites, and in presynapatic and postsynaptic membranes in the CNS. We will identify the protein domains responsible for subcellular localization by analysis of epitope-labeled chimeric channels in transgenic mice. We will investigate the transcriptional regulation of the SCN8A gene including identification of promoter(s) and enhancer elements. We will examine the regional distribution of alternative splicing in the brain and test a candidate site for RNA editing. Large scale genomic sequence of the SCN8A gene from human, mouse and puffer fish will be obtained and compared in order to identify evolutionarily conserved coding and noncoding sequences. We will generate mice with regulated conditional inactivation of SCN8A in specific neurons by targetting loxP sites into the SCN8A gene using homologous recombination. To produce models of human polygenic disease, we will cross SCN8A mutant mice with mice carrying null alleles of functionally related proteins such as SCN2A and the sodium channel beta subunits. This work will extend our knowledge of the physiological and cellular functions of SCN8A in the CNS and PNS and its role in neurological disease.