Carbohydrate Deficient Glycoprotein Syndromes: Models and Therapy

描述（由申请人提供）：先天性糖基化失调（先天性糖基化失调）是一种罕见的遗传性缺陷，存在于糖链（聚糖）的合成和蛋白质的添加过程中。所有14种类型（不同基因）的CDG-I患者都有不同基因的突变，但有一个共同的病变：缺乏完全的n -糖基化位点占用。同样，患者有许多共同的症状，但在不同类型内部和不同类型之间表现出广泛的临床差异。这些疾病没有脊椎动物模型，只有一种类型CDG-Ib有治疗方法。在这里，我们建议分析第一个可行的CDG- i小鼠模型，评估单一已知疗法，并将该疗法应用于目前无法治疗的CDG类型。CDG-Ib患者存在磷酸甘露糖异构酶（MPI, Fru-6-P_>Man-6-P）活性不足，并发肝功能障碍、纤维化、生长衰竭、蛋白丢失性肠病和凝血功能障碍。然而，膳食补充剂甘露糖通过一个次要的生物合成途径（Man’Man-6- p）增加甘露糖的通量，从而绕过缺陷，从而缓解几乎所有症状。缺乏PMM2 （Man-6-P’man -1- p）的CDG-Ia患者对甘露糖治疗没有反应，因为他们通过强大的MPI分解Man-6-P。注意，PMM2和MPI争夺相同的关键底物Man-6-P，它们的比例决定了其代谢通量。我们设计了一个拟态的Mpi等位基因来创建第一个可行的潜在CDG-I小鼠模型。迄今为止，对这些小鼠的分析显示肝脏病理进展和肠道蛋白损失增加。在Aim 1中，我们将确定这些小鼠是否表现出CDG-Ib患者的病理模型。目的2将确定半胚线如何响应环境压力。目的3将确定甘露糖是否能拯救（预防和/或逆转）拟形小鼠对病理的易感性，特别是蛋白质丧失性肠病和肝脏病理。由于不同类型的CDG有许多共同的病理，一种类型的成功治疗可能为治疗其他类型的CDG建立一个范例。因此，在Aim 4中，我们将与目前在子宫内死亡的pmm2缺陷小鼠一起繁殖mpi -亚形态小鼠。基于非常令人鼓舞的初步数据，我们预测在pmm2缺陷小鼠中提供甘露糖和遗传降低Mpi活性将通过增加Man-6-P进入耗尽糖基化途径的代谢通量来挽救致死表型。如果成功，该方法将表明将甘露糖通量重定向到耗尽糖基化途径具有治疗潜力，并将使高通量筛选寻找甘露糖通量增强化合物用于几种类型的CDG。

DESCRIPTION (provided by applicant): Congenital Disorders of Glycosylation (CDG) are rare inherited defects in sugar chain (glycan) synthesis and their addition to protein. All 14 types (different genes) of CDG-I patients have mutations in different genes, but share a common lesion: lack of full N-glycosylation site occupancy. Likewise, patients share many symptoms, but show broad clinical variations both within and between different types. There are no vertebrate animal models for these disorders and only one Type, CDG-Ib, has a therapy. Here we propose to analyze the first viable CDG-I mouse model, evaluate the single known therapy, and apply that therapy to currently untreatable types of CDG. CDG-Ib patients have insufficient phosphomannose isomerase (MPI, Fru-6-P_>Man-6-P) activity and develop liver dysfunction, fibrosis, failure to thrive, protein-losing enteropathy and coagulopathy. However, dietary supplements of mannose bypass the defect by increasing the flux of Mannose through a minor biosynthetic pathway (Man`Man-6-P) thus relieving nearly all symptoms. CDG-Ia patients, who are deficient in PMM2 (Man-6-P`Man-1-P), do not respond to mannose therapy because they catabolize Man-6-P via robust MPI. Note that PMM2 and MPI compete for the same critical substrate, Man-6-P, and their ratio determines its metabolic flux. We engineered a hypomorphic Mpi allele to create the first viable potential CDG-I mouse model. Analysis of these mice to date shows progressive hepatopathology and increased enteric protein loss. In Aim 1 we will determine whether these mice show pathology modeling CDG-Ib patients. Aim 2 will determine how hypomorphic lines respond to environmental stresses. Aim 3 will determine whether mannose rescues (prevents and/or reverses) the susceptibility of hypomorphic mice to pathology, specifically, protein-losing enteropathy and hepatic pathology. Since the various CDG types share many of the pathologies, successful treatment of one type may establish a paradigm to treat others. Therefore, in Aim 4 we will breed our Mpi-hypomorphic mice with Pmm2-deficient mice that currently die in utero. Based on highly encouraging preliminary data, we predict that providing mannose and genetically reducing Mpi activity in Pmm2-deficient mice will rescue the lethal phenotype by increasing the metabolic flux of Man-6-P into the depleted glycosylation pathway. If successful, this approach will show that redirecting mannose flux into the depleted glycosylation pathway has therapeutic potential and would empower high-throughput screening search for mannose flux-enhancing compounds for several types of CDG. PUBLIC HEALTH RELEVANCE: We will study the first mouse model of a rare human genetic disorder in protein glycosylation, offer a likely therapy, and apply the model/therapy to treat other human glycosylation disorders.