Generation and characterization of in vivo models of Small Fiber Neuropathy

描述(由申请人提供)： 小纤维神经病(SFN)是一种神经退行性疾病，其特征是无髓C-、小髓鞘Ad-和自主神经纤维的丢失，并与感觉和自主神经功能障碍有关，包括灼热、针刺和松弛疼痛和自主神经症状，这些症状往往难以治疗。SFN与多种原因有关，包括糖尿病、酒精中毒、毒素(包括橙剂)、艾滋病毒、抗肿瘤治疗和自身免疫性疾病，但相当大比例的SFN是特发性的，没有明显的原因。我们最近证实，在近30%的SFN患者中，钠通道Nav1.7存在功能增益变异，没有其他明显原因。然而，与Nav1.7的功能获得变异或与SFN相关的多种原因中的任何一种，导致小纤维丢失和疼痛发作的分子级联尚不清楚。拟议的小型项目旨在通过在SCN9A等位基因上杂合插入人类功能获得变体SCN9A(Nav1.7)基因来创建敲打小鼠，以开发小纤维神经病的体内模型。在特发性SFN患者中已经发现了Nav1.7中的多个功能获得变体，我们对两个变体(I228M和G856M)的电生理学和形态学研究是寻求体内模型生成的特别有希望的候选。在我们的研究中，我们建立了敲入小鼠，并通过形态、全细胞膜片钳和行为学方法对其进行了表型表征。在不受这一建议资助的未来研究中，基因敲入小鼠将成为有价值的平台，在其中进行机制研究，以确定导致三叉神经轴突变性和感觉和自主神经功能障碍的分子途径(S)。预计体内模型的发展将使我们能够识别和测试新的治疗方法，以最大限度地减少人类小纤维神经病的轴突变性以及与纤维丢失相关的感觉和自主神经功能障碍。

DESCRIPTION (provided by applicant): Small fiber neuropathy (SFN) is a neurodegenerative disorder that is characterized by a loss of unmyelinated C-, small myelinated Ad- and autonomic fibers, and is associated with sensory and autonomic dysfunctions, including burning, pin-prick and lancinating pain and autonomic symptoms, which are often refractory to treatment. SFN has been linked to multiple causes, including diabetes, alchoholism, toxins, including Agent Orange, HIV, anti-neoplastic treatments, and autoimmune disorders, but a substantial percentage of SFN are idiopathic, with no apparent cause. We have recently demonstrated the presence of gain-of-function variants in sodium channel Nav1.7 in nearly 30% of patients with SFN and no other apparent cause. However, the molecular cascade leading to small fiber loss and onset of pain associated with the gain- of-function variants in Nav1.7, or any of the multiple causes linked to SFN, is not yet understood. The proposed Small Project is designed to develop an in vivo model of small fiber neuropathy by creating knock-in mice with heterozygous insertion of a human gain-of-function variant in the Scn9a (Nav1.7) gene at the Scn9a allelle. Multiple gain-of-function variants in Nav1.7 have been found in patients with idiopathic SFN, and our electrophysiological and morphological studies of two variants (I228M and G856M) as exceptionally promising candidates in which to pursue generation of in vivo models. For our studies, knock-in mice are generated and phenotypically characterized by morphological, whole-cell patch clamp and behavioral methods. In future studies not funded by this proposal, the knock-in mice will serve as valuable platforms in which to perform mechanistic studies to determine the molecular pathway(s) leading to axonal degeneration and the onset of sensory and autonomic dysfunction in SFN. It is also anticipated that the development of the in vivo models will allow us to identify and test novel therapeutic approaches to minimize axonal degeneration, and the sensory and autonomic dysfunctions associated with fiber loss, in human small fiber neuropathy.