CARBOHYDRATE DEFICIENT GLYCOPROTEIN SYNDROMES

碳水化合物缺乏性糖蛋白合成酶（CDGS）是N-糖基化的遗传缺陷，其导致严重的神经病变和发育延迟。CDGS中的两个主要缺陷是已知的，但许多其他缺陷是未知的。我们建议通过已经确立的和以前成功的方法来确定其中的一些。此外，我们发现了一种非神经学形式的CDGS，其表现为严重的危及生命的蛋白质丢失性肠病、低血糖和肠出血。主要缺陷是磷酸甘露糖异构酶（PMI，Fru-6< >Man-6-P）的95%缺乏。重要的是要分析额外的患者与这种类型的CDGS，因为饮食甘露糖补充剂有效地扭转所有的临床和生化异常。正在进行的甘露糖治疗的I期研究涵盖神经和胃肠道（PMI缺陷）患者。一个简单的等电聚焦试验血清转铁蛋白是诊断所有类型。为了识别新的缺陷并分析额外的PMI缺陷患者，我们计划：1. 分析碳水化合物缺乏的血清转铁蛋白上的糖链结构，作为可能的初级糖基化缺陷的指标。2.用糖前体代谢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im 2的结果，直接测定可能缺乏的生物合成酶。如果缺陷发生在已知的或高度保守的生物合成酶中，请确定特定的遗传病变。4.鉴定PMI活性缺陷患者的突变，并将其与临床状况联系起来。这些方法在鉴定人、哺乳动物细胞和酵母中糖基化突变体的缺陷方面非常成功。事实上，目前没有第二种选择。这是研究CDGS缺陷的第一个基础广泛的建议，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疗法的了解越来越多，我们希望发现更多类型的CDGS。对糖基化缺陷患者的分析将拓宽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.