Mechanisms of Disease and Treatment in Novel Metabolic Developmental Brain Disorders

项目摘要 我们最近发现了一种新的人类神经遗传性疾病，其由以下基因的功能缺失突变引起： 线粒体酶谷氨酸丙酮酸转氨酶2（GPT 2）。遗传代谢疾病，如GPT 2 疾病，提供了一个强大的透镜，研究代谢机制，在人类大脑。此外，代谢 疾病可以通过饮食限制或补充剂进行治疗。GPT 2疾病涉及 出生后大脑发育不良和进行性痉挛性截瘫。根据我们广泛的初步数据， 我们已经建立了针对GPT 2疾病的潜在治疗策略。为了指导对儿童的这些干预， 我们建议完成所需的临床前研究。GPT 2定位于线粒体，并在细胞周期中上调。 出生后的大脑发育GPT 2催化氨基从谷氨酸可逆加成到 丙酮酸，产生丙氨酸和α-酮戊二酸，三羧酸（TCA）循环中的代谢物。我们 初步数据为疾病机制提供了支持，其中GPT 2在神经元凋亡中起关键作用。 通过调节神经元丙氨酸的合成和回补来生长。回补（回补）是指代谢过程中， 补充TCA循环中间体的过程。回补在高生物合成期是重要的 当TCA循环中间体被消耗用于合成用于细胞生长的大分子时， 这一过程被称为cataplerosis。因此，此R 01应用程序的中心目标是定义 GPT 2介导的神经元发育和健康机制，并研究其机制的有效性。 基于治疗。目的1是集中在体内研究Gpt 2介导的运动神经元的生长。我们的GPT 2- null小鼠概括了疾病的关键方面，如后肢运动异常，类似于痉挛性 截瘫患者中可见。在目标1和目标2中，我们正在制定基于机制的救援战略， 通过在Gpt 2缺失动物的饮食中补充代谢物来治疗体内运动缺陷。目标3将 定义GPT 2介导的控制神经元生长和体外治疗的代谢机制。这些 研究是在原代小鼠神经元，以及在人类神经元（从干细胞），以翻译 回到人类的背景。我们拥有强大的多学科团队， 整合的转化方法，将以患者为导向的研究与实验模型联系起来。总的来说， 这项提案中的研究将对基础神经科学和治疗产生持续的影响 发展我们将评估可以在GPT 2患者中快速实施的治疗策略。 这种疾病目前没有已知的治疗方法。这一进展将为早期干预铺平道路， 潜在地，预防患有GPT 2疾病的患者的神经损伤。最后，这些研究具有广泛的 重要性，因为我们将定义生长和健康所需的基本代谢机制， 神经元，包括在各种神经系统疾病中易受伤害的长投射运动神经元。

PROJECT SUMMARY We have recently identified a novel human neurogenetic disorder caused by loss-of-function mutations in the mitochondrial enzyme glutamate pyruvate transaminase 2 (GPT2). Genetic metabolic diseases, such as GPT2 disease, offer a powerful lens to investigate mechanisms of metabolism in human brain. Also, metabolic diseases may be amenable to treatments via dietary restrictions or supplements. GPT2 disease involves postnatal undergrowth of brain and progressive spastic paraplegia. Based on our extensive preliminary data, we have established potential treatment strategies for GPT2 disease. To guide these interventions in children, we propose to complete needed pre-clinical studies. GPT2 localizes to mitochondria and is upregulated during postnatal brain development. GPT2 catalyzes the reversible addition of an amino group from glutamate to pyruvate, yielding alanine and a-ketoglutarate, a metabolite in the tricarboxylic acid (TCA) cycle. Our preliminary data provide support for disease mechanisms, wherein GPT2 plays a critical role in neuronal growth by regulating neuronal alanine synthesis and anaplerosis. Anaplerosis (filling-up) is the metabolic process whereby TCA cycle intermediates are replenished. Anaplerosis is important during high biosynthetic demand, when TCA cycle intermediates are consumed for synthesis of macromolecules for cell growth, a process known as cataplerosis. Therefore, the central objective of this R01 application is to define the role of GPT2-mediated mechanisms in neuronal development and health, and to study the efficacy of mechanism- based treatments. Aim 1 is focused on in vivo studies of Gpt2-mediated growth of motor neurons. Our Gpt2- null mouse recapitulates key aspects of disease, such as hindlimb motor abnormalities, akin to spastic paraplegia seen in patients. In Aim1 and in Aim 2, we are developing mechanism-based rescue strategies to treat motor defects in vivo through metabolite supplementation in the diets of Gpt2-null animals. Aim 3 will define GPT2-mediated metabolic mechanisms governing neuronal growth and treatments in vitro. These studies are in both primary mouse neurons, as well as in human neurons (from stem cells) in order to translate advances back to the human context. We have a strong and multidisciplinary team permitting a powerful integrated translational approach, bridging patient-oriented studies to experimental models. In summary, research in this proposal will have a sustained impact on both fundamental neuroscience and treatment development. We will evaluate therapeutic strategies that could be rapidly implemented in patients with GPT2 disease, which currently has no known treatment. This progress would pave the way for early intervention, and potentially, prevention of neurologic damage in patients with GPT2 disease. Finally, these studies have broad significance, as we will define basic metabolic mechanisms required for growth and health of long-projecting neurons, including long-projecting motor neurons that are vulnerable in a variety of neurological diseases.