Understanding the Mechanism and Preventing the Unique Neuropathology of Arginase Deficiency

项目概要/摘要 该项目的总体目标是：1）研究与脑梗死相关的独特神经病理学的病因学。 A1缺乏，一种尿素循环障碍，和2）广泛证明基于AAV的 肝脏基因治疗在预防这种疾病的特征方面是有效的，这是临床试验的前奏。A1 缺乏导致慢性高维生素B2血症，其特征在于进行性精神损害、痉挛， 生长迟缓，只有周期性发作的高氨血症。我们的最新和初步调查结果 实验室与A1缺陷小鼠已经证明了大量的解剖，超微结构和电- 基因敲除与野生型之间的生理差异。A1缺乏导致内源性兴奋性降低， 能力、功能性突触传递改变、树枝状结构减少、髓鞘发育障碍和减少 突触密度导致这些神经元异常的最可能机制是高精氨酸-或胍- 迪诺化合物介导的神经元和少突胶质细胞功能障碍。控制血浆精氨酸和胍- 在给予肝脏特异性基于AAV的基因治疗后， 各项措施得到大幅改善。在神经元、突触、髓鞘和回路中发现异常 水平已经开始阐明A1缺乏的功能缺陷。近缘毒素的鉴定 神经功能障碍的机制将为A1的潜在药物干预打开大门 除了基因治疗外，还可能为其他疾病的新疗法开辟道路， 髓鞘形成障碍是一个特征。初步数据：我们的研究小组（除其他发现外）：1）构建 并表征了A1缺陷小鼠; 2）证明了肝脏特异性重组 AAV; 3）证明只有低水平的尿素生成是生存所必需的; 4）表明基因治疗- 经处理的A1基因敲除小鼠没有明显的神经系统异常; 5）表明外周代谢 导致循环血浆精氨酸的控制;和6）显示A1基因表达的丧失导致 神经元的内在兴奋性、突触类型和数量、髓鞘形成和树突状结构异常。 在目标1中，少突胶质细胞功能障碍和死亡导致髓鞘形成障碍的假设是部分原因。 将测试A1缺乏症中神经元功能障碍的原因。在目标2中，假设胍基水平升高 化合物可以诱导内在兴奋性和突触传递的改变，这些改变与那些化合物类似。 在A1缺陷动物中观察到的。在目标3中，将确定A1缺乏是否会导致失衡 在兴奋和抑制，如果这种不平等主要是通过对体周抑制的影响。完成 这些研究将提供一个更好的理解和背后的机制的变化， 脑、神经元和突触在A1缺乏和高胆固醇血症中的作用， 肝A1基因治疗在预防这些异常中的作用，为这种治疗作为一种治疗方法提供了有力的证据。 这是它在这种进行性神经系统疾病患者中临床应用的前奏。

Project Summary/Abstract The overall goals of this project are to 1) investigate the etiology of the unique neuropathology associated with arginase 1 (A1) deficiency, a disorder of the urea cycle, and 2) to extensively demonstrate that AAV-based hepatic gene therapy is effective in preventing the features of this disorder as a prelude to a clinical trial. A1 deficiency results in chronic hyperargininemia characterized by progressive mental impairment, spasticity, and growth retardation, with only periodic episodes of hyperammonemia. Recent and preliminary findings from our laboratory with the A1-deficient mouse have demonstrated substantial anatomical, ultrastructural and electro- physiological differences between knockouts and wild types. A1 deficiency led to decreased intrinsic excita- bility, altered functional synaptic transmission, decreased dendritic arborization, dysmyelination and decreased synaptic density. The most likely mechanism causing these neuronal abnormalities is hyperarginine- or guani- dino compound-mediated dysfunction of neurons and oligodendrocytes. Controlling plasma arginine and guani- dino compounds following administration of liver-specific AAV-based gene therapy resulted in much of these measures being substantially improved. The finding abnormalities at the neuron, synapse, myelin, and circuit level have begun to elucidate the functional deficits in A1 deficiency. The identification of the proximate toxin and mechanism of neurodysfunction will open doors to potential pharmacological interventions for A1 deficiency in addition to gene therapy, and may open avenues to new therapies for other disorders where dysmyelination is a feature. Preliminary data: Our research group has (amongst other findings): 1) constructed and characterized the A1-deficient mouse; 2) demonstrated long-term survival with liver-specific recombinant AAV; 3) demonstrated that only low-level ureagenesis is necessary for survival; 4) shown that gene therapy- treated A1 knockout mice lack gross nervous system abnormalities; 5) shown that peripheral metabolism results in control of circulating plasma arginine; and 6) shown that loss of A1 gene expression results in abnormalities of intrinsic excitability, synapse type and number, myelination and the dendritic arbor of neurons. In Aim 1, the hypothesis that oligodendrocyte dysfunction and death result in dysmyelination and is in part the cause of neuronal dysfunction in A1 deficiency will be tested. In Aim 2, the hypothesis that elevated guanidino compounds can induce alterations in intrinsic excitability and synaptic transmission that are similar to those seen in A1 deficient animals will be tested. In Aim 3, it will be determined if A1 deficiency causes an imbalance in excitation and inhibition, and if this inequality is mainly through effects on perisomatic inhibition. Completion of these studies will provide a greater understanding of and the mechanism(s) behind the alterations in the brain, neurons, and synapses in A1 deficiency and hyperargininemia while demonstrating the efficacy of hepatic A1 gene therapy in preventing these abnormalities, providing strong evidence for this therapy as a prelude to its clinical adoption in patients with this progressive neurological disorder.