CARBOHYDRATE DEFICIENT GLYCOPROTEIN SYNDROMES

糖蛋白缺乏症(CDGs)是一种N-糖基化的遗传缺陷，可导致严重的神经损害和发育迟缓。CDG的两个主要缺陷是已知的，但其他许多缺陷是未知的。我们建议以行之有效和过往成功的方法，找出其中一些问题。此外，我们发现了一种非神经系统形式的CDG，表现为严重威胁生命的蛋白丢失性肠病、低血糖和肠道出血。主要缺陷是95%的磷酸甘露糖异构酶(PMI，Fru-6&lt；&gt；Man-6-P)缺乏。分析更多患有这种类型CDG的患者是很重要的，因为饮食甘露糖补充剂有效地逆转了所有的临床和生化异常。正在进行的甘露糖治疗的第一阶段研究涵盖神经和胃肠道(PMI缺乏)患者。一种简单的血清转铁蛋白等电聚焦试验对所有类型的患者都有诊断价值。为了识别新的缺陷并分析其他PMI缺陷患者，我们计划：1.分析糖类缺陷血清转铁蛋白的糖链结构，以此作为可能的原发糖基化缺陷的指标。2.用糖前体代谢性标记患者成纤维细胞，以评估蛋白质糖基化和所有生物合成中间体。3.根据im2的结果，直接检测可能缺失的生物合成酶。如果缺陷发生在已知的或高度保守的生物合成酶中，请确定特定的遗传损伤。4.确定PMI活性缺陷患者的突变，并将其与临床情况联系起来。这些久经考验的方法在鉴定人类、哺乳动物细胞和酵母中糖基化突变体的缺陷方面取得了巨大的成功。事实上，目前没有第二个选择可用。这是第一个研究CDG缺陷的广泛提案，通过将其与甘露糖试验相结合，它融合了基础科学和临床医学。随着我们对这些疾病和治疗方法有更多的了解，我们预计会发现更多类型的CDG。对糖基化缺陷患者的分析将扩大我们对糖生物学及其在人类糖基化疾病中的直接应用的理解。

Carbohydrate Deficient Glycoprotein Syndromes (CDGS) are genetic defects in N-glycosylation that cause severe neurological lesions and developmental delay. Two primary defects in CDGS are known, but many others are unknown. We propose to identify some of them by well- established and previously successful approaches. In addition, we discovered a non-neurological form of CDGS that presents with severe life- threatening protein-losing enteropathy, hypoglycemia, and intestinal bleeding. The primary defect is a 95% deficiency in phosphomannose isomerase (PMI, Fru-6< >Man-6-P). It is important to analyze additional patients with this type of CDGS since dietary mannose supplements effectively reverse all the clinical and biochemical anomalies. Ongoing Phase I studies of mannose therapy cover both neurological and gastrointestinal (PMI-deficient) patients. A simple isoelectric focusing test of serum transferrin is diagnostic for all types. To identify new defects and analyze additional PMI-deficient patients we plan to: 1. Analyze the structure of sugar chains on carbohydrate-deficient serum transferrin as an indicator of possible primary glycosylation defects. 2. Metabolically label patient fibroblasts with sugar precursor to assess protein glycosylation and all biosynthetic intermediates. 3.Based on results from im 2, directly assay biosynthetic enzymes likely to be deficient. If the defect occurs in known or highly conserved biosynthetic enzymes, identify the specific genetic lesions. 4. Identify mutations in PMI activity-deficient patients and relate these to their clinical conditions. These tried-and-true approaches have been highly successful for identify the defects of glycosylation mutants in man, mammalian cells and yeast. In fact, no second option is currently available. This is the first broad-based proposal to study CDGS defects, and by interfacing it with the mannose trials, it merges basic science and clinical medicine. As we learn more about these disorders and therapies, we expect to discover additional types of CDGS. Analysis of glycosylation-deficient patients will broaden our understanding ob both glycobiology and its immediate application to human glycosylation diseases.