Pathogenesis of Myelin Protein Zero Neuropathies in Transgenic Mice

描述(由申请人提供)：我们建议确定髓鞘蛋白零(MPZ)相关神经病的细胞内发病机制。我们已经创造了一组独特的转基因小鼠，表达了MPZ的各种人类突变，这提供了原理证据，即来自不同细胞内位置的异常功能获得可以导致不同的髓鞘病变表型。在一个名为POS63del的模型中，我们已经确定了未折叠蛋白反应(UPR)。我们的假设是，在远离髓鞘的细胞内位置引发髓鞘病变的突变蛋白会产生更严重的神经病变，因为它们更普遍地扰乱雪旺细胞(通过凋亡杀死它们)或髓鞘蛋白质和脂肪合成的程序。在这里，我们将利用我们的模型，特别是POS63del小鼠，来了解突变蛋白在细胞内的保留如何产生脱髓鞘。我们将充分评估POS63del神经中的UPR下游介质，并探索S63改变如何产生未折叠的蛋白质。我们将从基因上消除未折叠的蛋白反应介质CHOP，并表征其对神经病的影响，以表明UPR导致脱髓鞘神经病。我们将系统地鉴定病变神经中CHOP转录因子的靶基因，以验证我们的假设，即对关键调节因子或髓鞘蛋白和脂肪合成程序的多个成员具有毒性作用。最后，我们将在一个新的蛋白酶体指示性小鼠中探索UPR是否诱导低效的蛋白酶体功能，从而改变PMP22等蛋白质的生理降解，从而诱导PMP22过表达的神经病。Charcot Marie Tooth遗传性神经病在美国影响15万人，在全球影响300万人，并造成重大终身残疾和重大经济损失。这些神经疾病中约有四分之一是由允许毒素1蛋白表达的突变引起的，这些突变干扰了雪旺细胞在神经中形成和维持髓鞘的能力。人们对毒性机制知之甚少。这项研究将确定其中一些机制，并为遗传性神经疾病提供潜在的治疗策略。同样的机制和策略也可能与广泛的与蛋白质折叠错误相关的疾病有关，包括阿尔茨海默病和糖尿病。

DESCRIPTION (provided by applicant): We propose to identify the intracellular pathogenesis of Myelin Protein Zero (MPZ)-related neuropathies. We have created a unique set of transgenic mice expressing various human mutations of Mpz that provide proof of principle that gain of abnormal function, deriving from diverse intracellular locations, can cause variable myelinopathy phenotypes. In one model, POS63del, we have identified the unfolded protein response (UPR). Our hypothesis is that mutant proteins that elicit myelinopathies from intracellular locations away from myelin, produce more severe neuropathy because they more generally perturb Schwann cells (kill them by apoptosis) or the program of myelin protein and lipid synthesis. Here we will exploit our models, and in particular POS63del mice, to understand how intracellular retention of mutant proteins produces demyelination. We will fully evaluate the UPR downstream mediators in POS63del nerves, and explore how the S63 alteration produces an unfolded protein. We will genetically eliminate the unfolded protein response mediator, CHOP, and characterize the effect on neuropathy to show that the UPR causes demyelinating neuropathy. We will systematically identify target genes of the CHOP transcription factor in diseased nerve, in order to test our hypothesis that the 'toxic' effect is on pivotal regulators, or multiple members of the program of myelin protein and lipid synthesis. Finally, we will explore in a novel proteasome indicator mouse whether the UPR induces inefficient proteasome function and thereby alters the physiological degradation of proteins such as PMP22, thereby inducing a PMP22 overexpression neuropathy. Charcot Marie Tooth hereditary neuropathies affect 150,000 people in the US and 3,000,000 people worldwide and account for significant lifelong disability and important economic loss. About one quarter of these neuropathies result from mutations that permit the expression of 'toxic1 proteins that interfere with the capacity of Schwann cells to form and maintain myelin in nerves. Little is known about the mechanisms of toxicity. This study will identify some of these mechanisms, and inform potential therapeutic strategies for hereditary neuropathies. The same mechanisms and strategies may also be relevant to the broad category of diseases associated with misfolded proteins including Alzheimer disease and Diabetes.