Development of Animal Models of Anti-MuSK Myasthenia

描述(由申请人提供)：抗肌肉特异性激酶(Musk)肌无力(AMM)是一种新描述的神经肌肉传递疾病，其特征是疲倦无力、肌肉萎缩和针对Musk的循环抗体(Abs)，Musk是一种跨膜受体激酶，对这种突触的形成至关重要。AMM与重症肌无力(MG)的不同之处在于其严重性、更多的局限性软弱和相关的肌肉萎缩。值得注意的是，人们对其发病机制或病因知之甚少，包括是否对麝香有伴随的细胞免疫反应，以及异常的神经肌肉传递和肌肉萎缩的机制。这种疾病的治疗方法几乎完全未知。目前的临床实践是使用为(血清阳性)MG开发的治疗方案。然而，积累的数据表明，许多这些治疗方法，如胆碱酯酶抑制剂、胸腺切除术和免疫球蛋白输注，效果甚微。我们的总体目标是开发更具体和有效的AMM治疗方法。为了实现这一目标，我们在Lewis大鼠身上建立了AMM的动物模型，称为实验性AMM(EAMM)，作为分析人类疾病发病机制的平台，包括活跃在神经肌肉接头(NMJ)的机制和对该突触的免疫攻击机制。这种由单次注射麝香60亚型蛋白诱导的模型疾病相当严重，导致疲劳性虚弱和肌肉萎缩，导致27天内死亡，同时NMJ的突触后和突触前成分都严重中断。拟议的研究将解决这样的假设，即AMM是一种抗体介导的疾病，并且麝香抗体在成熟的NMJ改变麝香的功能，从而导致这种疾病特有的虚弱和肌肉萎缩。这一假设的一个推论是，穆斯克除了在发育中的NMJ中扮演已知的角色外，在维持成熟突触方面也发挥着重要作用。第一个具体目的是通过临床、电生理学和形态学研究分析EAMM中NMJ的致病机制，重点是MASK激活的信号转导通路。第二个特定目的是通过评估这些动物对麝香的抗体和T细胞反应，以及用来自EAMM血清的免疫球蛋白和来自EAMM脾和淋巴结的淋巴细胞被动转移疾病，来分析EAMM自身免疫反应的性质。 公共卫生相关性：相关性：关于抗肌肉特异性激酶(Musk)肌无力(AMM)的发病机制或病因，包括穆斯克抗体是否事实上是致病的，是否存在伴随的细胞免疫反应，以及异常的神经肌肉传递和肌肉萎缩背后的机制，人们知之甚少。这种疾病的治疗也几乎完全未知。该项目将提供确定AMM潜在机制的手段，以确定新的治疗方法，并为测试这些治疗方法提供动物模型。

DESCRIPTION (provided by applicant): Anti-muscle-specific kinase (MuSK) myasthenia (AMM) is a newly-described disease of neuromuscular transmission characterized by fatigable weakness, muscle wasting and circulating antibodies (Abs) to MuSK, a transmembrane receptor kinase crucial to the formation of this synapse. AMM differs from myasthenia gravis (MG) in its severity, the more focal nature of the weakness and the associated muscle wasting. Remarkably little is known concerning its pathogenesis or etiology, including whether there is an accompanying cellular immune response to MuSK and what mechanisms underlie the abnormal neuromuscular transmission and muscle wasting. The treatment of this disease is nearly completely unknown. Current clinical practice is to use the treatment protocols developed for (seropositive) MG. However, data have accumulated demonstrating that many of these treatments, e.g. cholinesterase inhibitors, thymectomy and immunoglobulin infusion, are minimally effective. Our overall goal is to develop more specific and effective treatments of AMM. To accomplish this, we have produced an animal model of AMM in Lewis rats, termed experimental AMM (EAMM), to serve as a platform for analysis of the pathogenic mechanisms underlying the human disease, including the mechanisms active at the neuromuscular junction (NMJ) and the mechanisms underlying the immune attack on this synapse. The model disease, which is induced by a single injection of the MuSK 60 isoform of the protein is quite severe, resulting in fatigable weakness and muscle wasting leading to death within 27 days, along with severe disruption of both the postsynaptic and presynaptic components of the NMJ. The proposed studies will address the hypothesis that AMM is an Ab-mediated disease and that the MuSK Abs alter the function of MuSK at the mature NMJ, thereby inducing the weakness and muscle wasting that are characteristic of this disease. A corollary of that hypothesis is that MuSK, in addition to its known role in the developing NMJ, plays an important role in the maintenance of the mature synapse. The first specific aim involves the analysis of the pathogenic mechanisms operative at the NMJ in EAMM through clinical, electrophysiologic and morphologic studies of the NMJ, focusing on the signal transduction pathways activated by MuSK. The second specific aim analyzes the nature of the autoimmune response in EAMM by assessing both the Ab and T cell responses to MuSK in these animals, along with studies of passive transfer of the disease with both immunoglobulin derived from EAMM serum and lymphocytes from EAMM spleens and lymph nodes. PUBLIC HEALTH RELEVANCE: Relevance: Remarkably little is known concerning the pathogenesis or etiology of anti-muscle-specific kinase (MuSK) myasthenia (AMM), including whether the MuSK Abs are, in fact, pathogenic, whether there is an accompanying cellular immune response and what mechanisms underlie the abnormal neuromuscular transmission and muscle wasting. The treatment of this disease is also nearly completely unknown. This project will provide the means for determining the underlying mechanisms in AMM in order to identify new treatments and provide an animal model for testing these treatments.