Wang R, McFarland J G, Kekomaki R, Newman P J
Blood Research Institute, Blood Center of Southeastern Wisconsin, Milwaukee 53233.
Blood. 1993 Dec 1;82(11):3386-91.
A new platelet alloantigen, termed CA, has recently been implicated in a case of neonatal alloimmune thrombocytopenia (NATP) in a Filipino family in Canada. Maternal anti-CA serum reacted with glycoprotein (GP) IIIa and maintained its reactivity after removal of high mannose carbohydrate residues from GPIIIa. The monoclonal antibody (MoAb) AP3 partially blocked binding of anti-CA to GPIIIa, suggesting that the CA polymorphism is proximal to the AP3 epitope. Platelet RNA polymerase chain reaction (PCR) was used to amplify the region of GPIIIa cDNA that encodes this region of the protein. DNA sequence analysis showed a G<==>A nucleotide substitution at base 1564 that results in an arginine (Arg) (CGG)<==>glutamine (Gln) (CAG) polymorphism in amino acid (AA) 489. Further analysis of PCR-amplified genomic DNA from 27 normal individuals showed that AA 489 is encoded by a mutational "hot spot" of the GPIIIa gene, as three different codons for the wild-type Arg489 of GPIIIa were also found. The codon usage for Arg489 was found to be: CGG (63%), CGA (37%), and CGC (< 1%). These frequency data were valuable in determining the relationship of the CA alloantigen to the serologically defined TU GPIIIa polymorphism that is present in low frequency in the Finish population. Analyses of PCR-amplified genomic DNA showed the CA and TU alloantigens to be identical at the molecular level. Definition of these new molecular variants of the beta 3 integrin chain should prove valuable in the diagnosis of NATP in these two geographically disparate populations, and it may also provide useful genetic markers for examining other pathologic variations of the GPIIb-IIIa complex.
一种名为CA的新血小板同种抗原，最近在加拿大一个菲律宾裔家庭的新生儿同种免疫性血小板减少症（NATP）病例中被发现。母体抗CA血清与糖蛋白（GP）IIIa发生反应，并且在从GPIIIa去除高甘露糖碳水化合物残基后仍保持其反应性。单克隆抗体（MoAb）AP3部分阻断了抗CA与GPIIIa的结合，这表明CA多态性靠近AP3表位。血小板RNA聚合酶链反应（PCR）用于扩增编码该蛋白质区域的GPIIIa cDNA区域。DNA序列分析显示在第1564位碱基处存在G<==>A核苷酸替换，导致氨基酸（AA）489处的精氨酸（Arg）（CGG）<==>谷氨酰胺（Gln）（CAG）多态性。对来自27名正常个体的PCR扩增基因组DNA的进一步分析表明，AA 489由GPIIIa基因的一个突变“热点”编码，因为还发现了GPIIIa野生型Arg489的三种不同密码子。发现Arg489的密码子使用情况为：CGG（63%）、CGA（37%）和CGC（<1%）。这些频率数据对于确定CA同种抗原与在芬兰人群中低频存在的血清学定义的TU GPIIIa多态性之间的关系很有价值。对PCR扩增基因组DNA的分析表明，CA和TU同种抗原在分子水平上是相同的。β3整合素链这些新分子变体的定义对于诊断这两个地理位置不同人群中的NATP应该是有价值的，并且它还可能为检查GPIIb-IIIa复合物的其他病理变异提供有用的遗传标记。
