A new platelet polymorphism Duva+, localized within the RGD binding domain of glycoprotein IIIa, is associated with neonatal thrombocytopenia

Abstract

IntroductionThe platelet membrane glycoprotein (GP) IIb-IIIa complex or ␣ IIb ␤ 3 belongs to the integrin family of heterodimeric adhesion receptors involved in cell-matrix and cell-cell interactions. 1 This complex can bind ligands containing the Arg-Gly-Asp (RGD) sequence, such as fibrinogen, von Willebrand factor, vitronectin, and fibronectin. It plays a major role in platelet aggregation by interacting with the C-terminal part of the ␥ chain of fibrinogen. 2,3 The genes coding for GP IIb and GP IIIa are highly polymorphic. Most of the human platelet alloantigen (HPA) systems described are carried by the GP IIb-IIIa complex, and most of them are localized on the GP IIIa subunit: , and one unclassified private antigen Oe a . [4][5][6][7][8][9][10][11] Only 2 of the platelet antigen systems, HPA-3 and -9, reside on GP IIb, 12,13 and the genetic origin of the Va a antigen remains to be determined. 14 These antigenic systems result from a single base-pair substitution with the exception of Oe a , which depends on an in-frame deletion of 3 bases. 11 Platelet alloantigen systems are involved in neonatal alloimmune thrombocytopenia (NAIT), posttransfusion purpura, and refractoriness to platelet transfusions. NAIT is characterized by the destruction of fetal or newborn platelets by a maternal antibody elicited by the maternofetal platelet antigen incompatibility. During the course of the severe thrombocytopenia in the fetus or the newborn, there is a risk of intracerebral hemorrhage leading to death or neurologic impairment. The incidence of NAIT has been shown to be 1 per 800 to 1000 live births. 15 Most NAIT in Caucasians involves HPA-1 16 or HPA-5 17 (GP Ia polymorphism 18 ) maternofetal incompatibilities.We describe here a case of severe NAIT due to a new alloantigen Duv aϩ localized on GP IIIa. The genetic determination revealed a single base-pair substitution, CϾT, at the GP IIIa complementary DNA (cDNA) position 517. This leads to a threonine/isoleucine dimorphism at position 140 of the mature GP IIIa. The Duv aϩ form of the GP IIb-IIIa complex expressed in Cos cells shows this polymorphism is responsible for the alloimmunization and the consequent NAIT. The Duv aϩ polymorphism that was localized in the RGD binding site of GP IIIa could affect the ␣ IIb ␤ 3 function. Because no individuals homozygous for Duv aϩ were available, stable cell lines expressing the Duv aϩ form of GP IIb-IIIa were produced to study a possible effect of the Duv aϩ substitution on integrin function. Materials and methods Case reportWe report a 30-year-old white woman (Duv), para 4, gravida 4, who gave birth to a full-term male child with a severe thrombocytopenia at birth (platelets 17 ϫ 10 9 /L) associated with minor bruises and petechiae. The child was otherwise healthy (Apgar score 9 of 10). He was treated with a total of 1.6 g/kg intravenous immunoglobulin G (IgG) over 24 hours. On day 3, the platelet count had increased to 139 ϫ 10 9 /L, and the outcome was favorable. Neonatal thrombocytopenia was not recorded in any of the siblin...

αIIbβ3 integrin: new allelic variants in Glanzmann thrombasthenia, effects onITGA2BandITGB3mRNA splicing, expression, and structure-function

“…It might indirectly impair the interaction(s) of the a5 and/or a6 helix with the b-propeller. The last four mutations described, p.K137Q [Peterson et al, 2009], p.T140I (HPA-16bw) [Jallu et al, 2002], p.R143Q (HPA-4) [Wang et al, 1992] and p.T195N (HPA-17bw) [Stafford et al, 2008] only lead to allelic variants involved in alloimmune thrombocytopenia that are not related to GT phenotype. All these amino acids locate at the surface of the b-I domain with their side chains directed outside.…”

“…Genomic DNA was isolated from peripheral blood according to a published procedure [Jallu et al, 2002] or by using the MagNA Pure Compact Instrument and the Nucleic Acid Isolation Kit I (Roche Diagnostics, Meylan, France). In some cases, DNA samples were obtained by using QIAamp DNA Blood Mini kit (Qiagen, Courtaboeuf, France).…”

“…Site-directed mutagenesis and in vitro expression in COS-7 cells were done as previously described [Jallu et al, 2002] or by using the QuikChange s II XL Site-Directed Mutagenesis Kit (Agilent Technologies, Massy, France) according to the manufacturer's instructions. In some mutagenesis experiments, plasmid pcDNA3.1-Zeo containing the aIIb cDNA was used instead of pcDNA3.1-Neo (Invitrogen, Cergy Pontoise, France).…”

Three novel β3 domain-deletion peptides for the sensitive and specific detection of HPA-4 and six low frequency β3-HPA antibodies

“…Sera containing alloantibodies against low frequency HPAs, HPA-6bw, -7bw, -8bw and -16bw and three for HPA-11bw, were provided by the laboratories which discovered the respective alloantigen, most of which have been described previously [10,[14][15][16][17][18][19][20]. Of the five anti-HPA-4a sera samples, A1 and A2 were from volunteer blood donors and the remainder were from FMAIT cases.…”

New low‐frequency platelet glycoprotein polymorphisms associated with neonatal alloimmune thrombocytopenia

“…In recent years, other PLT‐specific alloantigens have been identified but, with the exception of HPA‐15a/b (Govb/a) carried on CD109, 10 each of the new systems consists of one common allele and a second quite rare allele having a gene frequency less than 0.01 in the general population. Twelve antigen systems containing one rare and one common allele have been designated HPA‐4, HPA‐6 to ‐14, HPA‐16, and HPA‐17 9,11,12 . To date, only one of the high‐frequency alleles (HPA‐4a) has been shown to cause maternal immunization, 13 owing presumably to the fact that very few women are homozygous for a “private” antigen and are thus susceptible to immunization by its high‐frequency counterpart.…”