1型糖基化(CDG-I)的先天性疾病包括一组27个具有异质性多系统表型的遗传缺陷,主要表现为非特异性神经症状。CDG-I的生化标志是转铁蛋白上部分不存在完全N-聚糖。然而,ALG1-CDG的诊断性N-四糖和其他一些CDG的高甘露糖N-聚糖的增加的最新发现表明,聚糖结构分析具有发现CDG-I基因的潜力。我们通过高分辨率四极杆飞行时间质谱分析了111名已知(n=75)或未解决(n=36)遗传原因的CDG-I患者的相对丰度。我们设计了单分子分子倒置探针(smMIP),用于基于特定的N-聚糖签名对CDG-I候选基因进行测序。具有已知缺陷的患者中的糖组学分析揭示了新的特征,例如ALG2-CDG患者中的N-四糖和新的岩藻糖基化的N-五糖作为ALG1-CDG的特异性糖标志物。此外,在ALG3-中发现了组特异性高甘露糖N-聚糖标记,ALG9-,ALG11-,ALG12-,RFT-,SRD5A3-,DOLK-,DPM1-,DPM3-,MPDU1-,ALG13-CDG,和遗传性果糖不耐受.进一步的差异分析揭示了高甘露糖特征,ALG12-和ALG9-CDG的特征。通过糖组学分析预测36例迄今为止尚未解决的CDG-I和随后的smMIP测序的患者的候选基因导致78%的已解决病例的产量(28/36)。联合血浆糖组学分析和候选基因的靶向smMIP测序是鉴定CDG-I患者队列中的致病突变的有力方法。
Congenital disorders of glycosylation type 1 (CDG-I) comprise a group of 27 genetic defects with heterogeneous multisystem phenotype, mostly presenting with nonspecific neurological symptoms. The biochemical hallmark of CDG-I is a partial absence of complete N-glycans on transferrin. However, recent findings of a diagnostic N-tetrasaccharide for ALG1-CDG and increased high-mannose N-glycans for a few other CDG suggested the potential of glycan structural analysis for CDG-I gene discovery. We analyzed the relative abundance of total plasma N-glycans by high resolution quadrupole time-of-flight mass spectrometry in a large cohort of 111 CDG-I patients with known (n = 75) or unsolved (n = 36) genetic cause. We designed single-molecule molecular inversion probes (
smMIPs) for sequencing of CDG-I candidate genes on the basis of specific N-glycan signatures. Glycomics profiling in patients with known defects revealed novel features such as the N-tetrasaccharide in ALG2-CDG patients and a novel fucosylated N-pentasaccharide as specific glycomarker for ALG1-CDG. Moreover, group-specific high-mannose N-glycan signatures were found in ALG3-, ALG9-, ALG11-, ALG12-, RFT1-, SRD5A3-, DOLK-, DPM1-, DPM3-, MPDU1-, ALG13-CDG, and hereditary fructose intolerance. Further differential analysis revealed high-mannose profiles, characteristic for ALG12- and ALG9-CDG. Prediction of candidate genes by glycomics profiling in 36 patients with thus far unsolved CDG-I and subsequent
smMIPs sequencing led to a yield of solved cases of 78% (28/36). Combined plasma glycomics profiling and targeted
smMIPs sequencing of candidate genes is a powerful approach to identify causative mutations in CDG-I patient cohorts.