Pakdeesuwan K, Siripanyaphinyo U, Pramoonjago P, Pattanapanyasat K, Wilairat P, Kinoshita T, Wanachiwanawin W
Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.
Southeast Asian J Trop Med Public Health. 1997;28 Suppl 3:58-63.
The genetic and biochemical defects underlying paroxysmal nocturnal hemoglobinuria (PNH) have recently been elucidated. The deficiency of the surface expression of glycosylphosphatidylinositol (GPI)-anchored proteins caused by a somatic mutation of the PIG-A gene, an X-chromosomal gene that participates in the first step of the GPI anchor synthesis, has been shown to be responsible for PNH in all patients. The mutations of PIG-A studied to date are highly heterogeneous. They are however mainly of the frameshift type (61.5%). The characteristic abnormalities of PNH phenotypes has also been shown especially by DAF- and/or CD59-based fluorescent immunocytometry. A great degree of heterogeneity in the patterns and levels of expression of GPI-anchored proteins in various cell types was demonstrated indicating a discrepancy of lineage involvement. In this investigation, major blood cell populations, i.e erythrocytes and granulocytes were analyzed immunophenotypically, the mutations of PIG-A were identified by heteroduplex analysis and nucleotide sequencing and the consequences of PIG-A mutations were observed. All the mutations identified in 9 patients with PNH resulted in complete loss of function as clones of affected granulocytes completely negative for CD59 expression were shown in all patients. Interestingly, granulocytes in these patients contained variable proportions of affected cells varied from 50% to 100% and four of the patients had erythrocytes with diminished expression of GPI-anchored DAF and CD59 coexisting with normal and completely negative cells. Immunophenotypic analysis of reticulocytes in peripheral blood of patients with PNH demonstrated the conserved patterns of DAF and CD59 expression in circulating erythroid cells and the discrepancies between granulocytic and erythroid lineages. These findings suggested that the characteristics of abnormal phenotypes which appear to be highly variable between different hematopoietic lineages are not solely caused by mutation of PIG-A but are influenced by other factor(s).
阵发性睡眠性血红蛋白尿（PNH）潜在的遗传和生化缺陷最近已被阐明。由PIG - A基因（一个参与糖基磷脂酰肌醇（GPI）锚合成第一步的X染色体基因）的体细胞突变导致的GPI锚定蛋白表面表达缺陷，已被证明是所有PNH患者发病的原因。迄今为止所研究的PIG - A突变具有高度异质性。然而，它们主要是移码类型（61.5%）。PNH表型的特征性异常也尤其通过基于衰变加速因子（DAF）和/或CD59的荧光免疫细胞术得以显示。在各种细胞类型中，GPI锚定蛋白的表达模式和水平存在很大程度的异质性，这表明不同谱系受累存在差异。在本研究中，对主要血细胞群体，即红细胞和粒细胞进行了免疫表型分析，通过异源双链分析和核苷酸测序鉴定了PIG - A突变，并观察了PIG - A突变的后果。在9例PNH患者中鉴定出的所有突变均导致功能完全丧失，因为所有患者中受影响的粒细胞克隆对CD59表达均呈完全阴性。有趣的是，这些患者的粒细胞中受影响细胞的比例各不相同，从50%到100%不等，其中4例患者的红细胞中GPI锚定的DAF和CD59表达减少，同时存在正常和完全阴性的细胞。对PNH患者外周血中网织红细胞的免疫表型分析表明，循环红细胞中DAF和CD59的表达模式具有保守性，而粒细胞系和红细胞系之间存在差异。这些发现表明，不同造血谱系之间异常表型特征的高度变异性似乎不仅仅是由PIG - A突变引起的，还受到其他因素的影响。
