Molecular Basis of Charcot-Marie-Tooth Disease

腓骨肌萎缩症（CMT）是一种最常见的遗传性神经病。CMT 1型（CMT 1）是该病的主要形式，是一种遗传异质性疾病，已鉴定出许多相关基因。然而，在许多日本患者中尚未发现致病突变。我们试图建立可靠和简单的诊断方法，以明确日本患者的分子基础。我们还研究了在周围神经系统信号转导中起重要作用的Nav 1.6通道的生理特性。我们对143例CMT1患者进行了研究，初步鉴定了40例患者的CMT1A重复。对非CMT1A基因重复的患者，采用变性梯度凝胶电泳（DGGE）和变性高效液相色谱（DHPLC）检测PMP 22、Po、Cx32、EGFR 2、LITAF、GDAP 1、MTMR 2和PRX基因突变。我们确定了7例PMP22突变患者，16例Po突变患者，13例Cx32突变患者，1例EGR2突变患者，1例MTMR2突变患者和3例PRX突变患者。与国外资料相比，CMT1A基因重复引起的病例较少，许多患者（44%）的病因不明。我们分离了Nav 1.6通道的cDNA，并利用膜片钳技术在异源表达细胞系统中检测了Nav 1.6通道的生物物理特性。我们在tsA201细胞中观察到Nav 1.6通道的大的持续电流，然而，与锚蛋白G共表达的持续电流显著降低。提示Ankyrin G的调节可能是Nav106通道位点依赖性电生理特性的基础。

Charcot-Marie-Tooth disease (CMT) is a most common hereditary neuropathy. CMT type 1 (CMT1), the major form of the disease, is a genetically heterogeneous disease and many responsible genes have been identified. However, disease-causing mutations have not been identified in many Japanese patients. We tried to establish the reliable and easy diagnostic method to make clear the molecular basis of Japanese patients. We also studied physiological properties of Nav 1.6 channel, which plays a significant role for signal transduction in the peripheral nervous system.We studied 143 patients with CMT1 and initially identified the CMT1A duplication in 40 patients. As for the patients without the CMT1A duplication, we screened the mutations of PMP22, Po, Cx32, EGR2, LITAF, GDAP1, MTMR2 and PRX using denaturing gradient gel electrophoresis (DGGE) and denaturing high performance liquid chromatography (DHPLC). We identified 7 patients with PMP22 mutations, 16 patients with Po mutations, 13 patients with Cx32 mutations, 1 patient with EGR2 mutation, 1 patient with MTMR2 and 3 patients with PRX mutations. Compared with the data from foreign countries, the patients due to CMT1A duplication were few and many patients (44%) were not identified their etiologies. Further study is needed to clarify the molecular basis of Japanese patients.We previously isolated cDNA of Nav 1.6 channel and examined biophysical properties of Nav 1.6 in heterologous expression cell systems using patch clamp method. We observed large persistent current of Nav 1.6 Channel in tsA201 cells however, the persistent current was significantly reduced by the co-expression with ankyrin G. It suggested that modulation by ankyrin G may underlie site-dependant electrophysiological Characteristics of Nav 106 channels.