The asialoglycoprotein receptor minor subunit gene (ASGR2) contributes to pharmacokinetics of factor VIII concentrates in Hemophilia A

Background The asialoglycoprotein receptor (ASGPR) binds with high affinity factor VIII (FVIII) through its N-linked oligosaccharides. However, its contribution to the wide inter-individual variation of infused FVIII pharmacokinetics (PK) in Hemophilia A (HA) is unknown. Objective To investigate the variability in FVIII PK outcomes in relation to genetic variation in the ASGR2, encoding the ASGPR2 subunit. Patients/Methods Thirty‐two HA patients with FVIII:C ≤ 2 IU/dL underwent 66 single dose FVIII PKs. PK parameters were evaluated in relation to ASGR2 5’ untranslated region (5’UTR) polymorphisms, that were investigated by recombinant and white blood cell RT-PCR approaches. Results The 5’UTR polymorphisms determine a frequent and conserved haplotype (HT1) in a regulatory region. The HT1 homozygotes may differ in the amounts of alternatively spliced mRNA transcripts and thus ASGPR2 isoforms. Compared to the other ASGR2 genotypes, the c.-95TT homozygotes (n=9), showed three-fold longer Alpha HL (3.60 h, 95% CI 1.44-5.76, p=0.006), and the c.-95TC heterozygotes (n=17) showed 25% shorter MRT (18.5 h, 15.0-22.0, p=0.038) and 32% shorter Beta HL (13.5 h, 10.9-16.0, p=0.016). These differences were confirmed in patients (n=27) undergoing PKs (n=54) with full-length FVIII only. In different linear regression models, the contribution of the ASGR2 genotypes remained significant after adjustment by ABO genotypes and VWF:Ag levels, and explained 14% (MRT), 15-18% (Beta HL) and 22% (Alpha HL) of parameter variability. Conclusions Infused FVIII distribution was modulated by frequent ASGR2 genotypes, independently from and together with ABO and VWF antigen levels, which has potential implications for genetically tailored substitutive treatment in HA.

ABO genotypes and the risk of esophageal and gastric cancers

Background Blood type has been associated with the risk of gastric cancer, but few studies have examined the association with esophageal squamous cell carcinoma (ESCC). Methods We conducted a case-control study using genotyping data of Chinese individuals, including cases of 2022 ESCC, 1189 gastric cardia adenocarcinoma, 1161 gastric noncardia adenocarcinoma, and 2696 controls. Genetic blood type was imputed using three single nucleotide polymorphisms. We used logistic regression to examine the association between blood type and the risk of each cancer. Results Compared to blood type O, the risk of ESCC was significantly elevated for blood type B and AB, with the highest risk for type AB (OR, 95%CI: 1.34, 1.07–1.67). Analysis of genotype suggested that the association of ESCC was from carrying the B allele. Similarly, blood type was significantly associated with gastric noncardia adenocarcinoma (P < 0.001) with risk significantly elevated in type A (1.37, 1.14–1.65) and AB (1.44, 1.10–1.89) compared to type O. Blood type was not associated with gastric cardia adenocarcinoma (P = 0.13). Conclusions This study provides novel insights into the association between blood type and the risk of ESCC and restricted previously observed association to only gastric noncardia cancer, providing important evidence to clarify the pattern of association and suggesting mechanisms of action.

ABO Genotype-Phenotype Discrepancy Due to Tri-Allelic ABO Genotypes and Its Resolution by Cloning-Sequencing and Chimerism Analysis

Abstract 4337 We investigated the molecular genetic basis of an ABO blood group discrepancy found incidentally in an individual with no transfusion or transplantation history. During routine preoperative blood grouping, red blood cells (RBCs) had a weak or mixed field reaction (double populations in a gel column) with anti-A, while serum typing showed the anti-B antibody. We sent the sample to a reference laboratory for ABO genotyping using sequencing analysis, and her genotype was reported to have O/O alleles. To resolve the genotype-phenotype discrepancy, we repeated the direct sequencing analysis and finally found a heterozygous insertion/deletion (indel) on exon 6, involving two major alleles and one minor allele. With cloning and sequencing analysis, we isolated the O01, O02, and A102 alleles, respectively. In addition, tri-allelic or tetra-allelic patterns in short tandem repeat (STR) loci were noted. Chimerism is rare, but it can cause genotype-phenotype discrepancies in blood grouping, parentage, or other genetic laboratory tests. The transfusion of chimeric RBCs was even reported to induce acute intravascular hemolysis. It is very difficult to correctly find heterozygous peaks without assuming their existence, especially when caused by a chimera. Consequently, separation by cloning or enrichment of minor alleles such as using the cold polymerase chain reaction is sometimes needed. A familial study of STR markers could also be a confirmatory test. Here, we report an ABO genotype-phenotype discrepancy due to tri-allelic ABO genotypes and its resolution by cloning sequencing and STR analysis. By cloning-sequencing analysis, the two major alleles O01 and O02 and one minor allele A102 were separated. A blank means the same base as the reference sequence. Bases in parentheses indicate minor peaks. Disclosures: No relevant conflicts of interest to declare.

ABO blood group genotypes, plasma von Willebrand factor levels and loading of von Willebrand factor with A and B antigens

SummaryABO blood group is a genetic determinant of von Willebrand factor (VWF) levels. We investigated the effect of ABO genotypes on VWF and factor VIII (FVIII) levels and on the degree to which VWF is loaded with A- and B-antigens, expressed as normalized ratios, nA-ratio and nB-ratio, respectively, in the Leiden Thrombophilia Study, a large case-control study on venous thrombosis. We found that the ABO locus had an allele-specific, dosage dependent effect on VWF and FVIII levels and on the loading of VWF with A-antigen and B-antigen. The highest mean nA- and nB-ratios were found in A 1 A 1 and BB genotypes, respectively. Four A1 O carriers had four 43-bp repeats in the minisatellite region of theABO gene in stead of the expected one repeat. All had a reduced nA-ratio compared to A 1 O carriers with one repeat in their A1 allele. The amount of A – and B- antigens expressed onVWF (nA-ratio and nB-ratio) explained about 18% (R2) of the variation in VWF levels.