Expression Of Blood Group Antigens Research Articles

Do Blood Group Antigens and the Red Cell Membrane Influence Human Immunodeficiency Virus Infection?

The expression of blood group antigens varies across human populations and geographical regions due to natural selection and the influence of environment factors and disease. The red cell membrane is host to numerous surface antigens which are able to influence susceptibility to disease, by acting as receptors for pathogens, or by influencing the immune response. Investigations have shown that Human Immunodeficiency Virus (HIV) can bind and gain entry into erythrocytes, and therefore it is hypothesized that blood groups could play a role in this process. The ABO blood group has been well studied. However, its role in HIV susceptibility remains controversial, while other blood group antigens, and the secretor status of individuals, have been implicated. The Duffy antigen is a chemokine receptor that is important in the inflammatory response. Those who lack this antigen, and type as Duffy null, could therefore be susceptible to HIV infection, especially if associated with neutropenia. Other antigens including those in the Rh, Lutheran and OK blood group systems have all been shown to interact with HIV. More recently, experiments show that cells which overexpress the Pk antigen appear to be protected against infection. These reports all demonstrate that red cell antigens interact and influence HIV infection. However, as the red cell membrane is complex and the pathogenesis of HIV multi-factorial, the role of blood group antigens cannot be studied in isolation.

Maternal Secretor Status Affects Oral Rotavirus Vaccine Response in Breastfed Infants in Bangladesh.

Secretor status controls mucosal histo–blood group antigen expression and is associated with susceptibility to rotavirus (RV) diarrhea, with nonsecretors less susceptible to symptomatic infection. The role of breast milk secretor status on oral live-attenuated RV vaccine response in breastfed infants has not been explored. In a monovalent G1P[8] RV vaccine (Rotarix) trial in Bangladesh, RV-specific plasma immunoglobulin A antibody seroconversion rates were higher among infants of maternal nonsecretors (39%) than infants of maternal secretors (23%; P = .001). Maternal status remained a significant predictor when correcting for infant status (P = .002). Maternal secretor status should be considered when interpreting oral RV vaccine responses in low- and middle-income settings.Clinical Trials Registration. NCT01375647.

Influence of histo blood group antigen expression on susceptibility to enteric viruses and vaccines.

Gastroenteritis results in substantial morbidity and mortality worldwide, especially in young children in low-and-middle-income settings. Rotavirus and norovirus are the leading causes of viral gastroenteritis. Although introduction of rotavirus vaccines into childhood immunization programmes has reduced disease burden, vaccine effectiveness remains low in developing countries. Norovirus is replacing rotavirus as the most common cause of diarrhea hospitalization in settings where rotavirus vaccines are highly effective. Genetically determined host factors, such as expression of histo blood group antigens (HBGAs) are hypothesized to play key roles in susceptibility to infections and gastroenteritis caused by these virus, as well as influence vaccine take. Epidemiology studies provide strong support for virus genotype-dependent effects of host HBGA expression, specifically secretor status on susceptibility to rotavirus and norovirus. Secretor-positive persons are significantly more susceptible to gastroenteritis caused by rotavirus P[8] genotype, and to infection with the GII.4 genotype of human norovirus. There is increasing data on the role of secretor status on rotavirus vaccine take but results are currently conflicting. For analyses involving young infants, maternal HBGA status is an important factor to be considered in future studies. Genetically determined HBGA expression influences susceptibility to enteric viruses of public health importance.

Association between the ABO blood group and primary knee osteoarthritis: A case–control study

BackgroundRecent studies have suggested association between the ABO blood group and inflammation, which was a crucial pathological process of primary knee osteoarthritis. The aim of this study was to investigate the association between the ABO blood group and primary knee osteoarthritis ​and the severity of primary knee osteoarthritis evaluated by the Kellgren/Lawrence score, as well as the histopathologic association in a subgroup of patients. MethodsWe performed a retrospective review of patients with primary knee osteoarthritis that served as the case group ​and a random sampling of healthy blood donors that served as the control group. The severity of knee osteoarthritis at the first outpatient visit was evaluated by the Kellgren/Lawrence scoring system. Further study was performed to investigate the expression of blood group antigens in synovial tissue of the knee in both cases and controls. ResultsA total of 1126 cases and 30299 controls were involved. The proportion of AB blood group was higher in the case group than in the control group (9.7% vs. 7.8%), and logistic regression revealed that the AB blood group was a risk factor of primary knee osteoarthritis (P ​= ​0.025 and 0.048 for univariate and multivariate analysis, respectively), independent of age (P ​= ​0.973) and sex (P ​= ​0.520). Patients of the blood group AB had a higher Kellgren/Lawrence score (P ​= ​0.017). The immunohistochemical study indicated association between LeY antigen and primary knee osteoarthritis (P ​= ​0.029). ConclusionsThis study suggested that the blood group AB was associated with primary knee osteoarthritis, as well as its radiological severity. Further study indicated that LeY antigen, which was related to the blood group, was associated with primary knee osteoarthritis. Translational potential of this articleThis study revealed that blood group AB and LeY antigen was associated with primary knee osteoarthritis, which shed new light on the nature of osteoarthritis, and the development of novel therapy for osteoarthritis.

Blood Group Antigen Expression in Isolated Human Liver Cells in Preparation for Implementing Clinical ABO-Incompatible Hepatocyte Transplantation

ABO blood group antigens in the liver are expressed mainly on endothelial cells or biliary epithelial cellsbut not on hepatocytes. This suggests that ABO-incompatible hepatocyte transplantation (ABOi-HTx) is theoretically feasible. However, the effects of stress on ABO blood group antigen expression caused by isolation and intraportal infusion require thorough investigation before ABOi-HTx can be implemented in clinical settings. Human hepatocytes were isolated from liver tissue obtained from liver resection or deceased donor livers. The expression of blood group antigens on cryopreserved human liver tissues and isolated hepatocyte smear specimens were examined by immunofluorescent staining. The effect of proinflammatory cytokines on blood group antigen expression of hepatocytes was evaluated by flow cytometry. Instant blood-mediated inflammatory reaction after hepatocyte incubation with ABO-incompatible whole blood was examined using the tubing loop model. Blood group antigens were mainly expressed on vessels in the portal area. In hepatocyte smear specimens, isolated hepatocytes did not express blood group antigens. In contrast, a subset of cells in the smear specimens of nonparenchymal liver cells stained positive. In the flow cytometry analysis, isolated hepatocytes were negative for blood group antigens, even after 4-h incubation with cytokines. Platelet counts and complement activation were not significantly different in ABO-identical versus ABO-incompatible settings in the tubing loop model. Our study showed that blood group antigens were not expressed on hepatocytes, even after isolation procedures or subsequent incubation with cytokines. This finding is an important step toward removing the restriction of ABO matching in hepatocyte transplantation. Our results suggest that ABOi-HTx is a feasible therapeutic option, especially in patients who require urgent treatment with freshly isolated hepatocytes, such as those with acute liver failure.

Blood group alters platelet binding kinetics to von Willebrand factor and consequently platelet function

AbstractBlood type O is associated with a lower risk of myocardial infarction. Platelets play a critical role in myocardial infarction. It is not known whether the expression of blood group antigens on platelet proteins alters platelet function; we hypothesized that platelet function would be different between donors with blood type O and those with non-O. To address this hypothesis, we perfused blood from healthy type O donors (n = 33) or non-O donors (n = 54) over pooled plasma derived von Willebrand factor (VWF) protein and purified blood type–specific VWF at arterial shear and measured platelet translocation dynamics. We demonstrate for the first time that type O platelets travel farther at greater speeds before forming stable bonds with VWF. To further characterize these findings, we used a novel analytical model of platelet interaction. Modeling revealed that the kinetics for GPIb/VWF binding rate are significantly lower for type O compared with non-O platelets. Our results demonstrate that platelets from type O donors interact less with VWF at arterial shear than non-O platelets. Our results suggest a potential mechanism for the reduced risk of myocardial infarction associated with blood type O.

Genetic Variants Within the Erythroid Transcription Factor, KLF1, and Reduction of the Expression of Lutheran and Other Blood Group Antigens: Review of the In(Lu) Phenotype.

Erythroid-specific Krüppel-like factor 1, or KLF1, is an integral transcriptional activator for erythropoiesis. Genetic variants within KLF1 can result in a range of erythropoietic clinical phenotypes from benign to significant. The In(Lu) phenotype refers to changes in the quantitative expression of blood group-associated red cell surface molecules due to KLF1 variants which are otherwise clinically benign. These clinically benign KLF1 variants are associated with a reduced expression of 1 or more red cell membrane proteins/carbohydrates that carry blood group antigens for the LU (Lutheran), IN (Indian), P1PK, LW (Landsteiner-Wiener), KN (Knops), OK, RAPH, and I blood group systems. This is of significance during routine serologic blood typing when expression falls below the test sensitivity and therefore impacts on the ability to accurately detect the presence of affected blood group antigens. This is of clinical importance because the transfusion requirements for individuals with the In(Lu) phenotype differ from those of individuals that have a true Lunull phenotype. With this review, we summarize the current body of knowledge with regard to the In(Lu) phenotype and associated KLF1 variants. Our review also highlights discordant reports and provides insights for future research and management strategies. Serological heterogeneity in blood group expression of In(Lu) individuals has been shown, but studies are limited by the low prevalence of the phenotype and therefore the small numbers of samples. They are further limited by availability and inconsistent application of serological reagents and varying test algorithms. With the advent of genome sequence-based testing, an increasing list of In(Lu)-associated KLF1 variants is being revealed. The spectrum of effects on blood group expression due to these variants warrants further attention, and a consistent methodological approach of studies in larger cohorts is required. We propose that a recently reported testing framework of standardized serological studies, flow cytometry, and variant analysis be adopted; and that the international databases be curated to document KLF1 variability and the resultant In(Lu) red cell blood group expression. This will provide better classification of KLF1 variants affecting blood group expression and allow for phenotype prediction from genotype, accurate typing of In(Lu) individuals, and better transfusion management of related challenging transfusion scenarios.

The role of genomics in transfusion medicine.

To summarize recent advances in red blood cell (RBC) blood group genotyping, with an emphasis on advances in the use of NGS next generation sequencing (NGS) to detect clinically relevant blood group gene variation. Genetic information is useful in predicting RBC blood group antigen expression in several clinical contexts, particularly, for patients at high-risk for allosensitization, such as multiple transfused patients. Blood group antigen expression is directed by DNA variants affecting multiply genes. With over 300 known antigens, NGS offers the attractive prospect of comprehensive blood group genotyping. Recent studies from several groups show that NGS reliably detects blood group gene single nucleotide variants (SNVs) with good correlation with other genetic methods and serology. Additionally, new custom NGS methods accurately detect complex DNA variants, including hybrid RH alleles. Thus, recent work shows that NGS detects known and novel blood group gene variants in patients, solves challenging clinical cases, and detects relevant blood group variation in donors. New work shows that NGS is particularly robust in identifying SNVs in blood group genes, whereas custom genomic tools can be used to identify known and novel complex structural variants, including in the RH system.

Application of immortalized human erythroid progenitor cell line in serologic tests to detect red blood cell alloantibodies.

Antibody screening in pretransfusion tests is necessary to avoid critical complications of blood transfusion. Although red blood cells (RBCs) expressing relevant alloantigen(s) have been used for serologic antibody screening, little attention has been given to the use of cell lines, in which blood group antigen gene(s) are transduced, as reagent RBCs for antibody screening. The use of an erythroid progenitor cell line for serologic tests was studied. The expression of blood group antigens of erythroid progenitor cells was analyzed by genotyping and flow cytometry. Serologic analysis including hemagglutination was performed using erythroid progenitor cells to evaluate their sensitivity for antibody detection. Overexpression of exogenous erythroid antigen by lentiviral transduction was carried out and investigated for antibody detection sensitivity. Erythroid progenitor cells contained a substantial amount of hemoglobin and expressed sufficient levels of blood group antigens to detect corresponding monoclonal antibodies. Furthermore, the cell line could acquire an exogenous RBC antigen after lentiviral transduction and detected corresponding monoclonal and alloantibodies with equal sensitivity to antigen-positive RBCs. Application of erythroid progenitor cell lines for screening for unexpected antibodies could be helpful in solving issues such as reagent availability associated with the conventional RBC-based assay. The genetic expandability of erythroid progenitor cell lines by gene modification techniques could lead to the development of more convenient reagent RBCs.

Effect of the Isolation Procedure and Inflammatory Cytokines on Blood Group Antigen Expression on Human Hepatocytes in Preparation for Investigating ABO-Incompatible Hepatocyte Transplantation

Effect of the Isolation Procedure and Inflammatory Cytokines on Blood Group Antigen Expression on Human Hepatocytes in Preparation for Investigating ABO-Incompatible Hepatocyte Transplantation

Inhibition of the Transcription Factor RUNX1 Causes Glycosyltransferase a Repression

Background: The ABO blood group system is unequivocally the most important in clinical transfusion medicine. Furthermore ABO is implicated in the development of a number of human diseases. The ABO antigens are not confined to RBCs but are widely expressed in a variety of human cells and tissues. Thus, ABO matching is critical not only in blood transfusion but also in cell, tissue and organ transplantation. The molecular genetic basis of the ABO system has been known since 1990. However, despite extensive investigations about regulation of ABO blood group receptor expression, the mechanism is not fully resolved. Previously we found that miRNAs plays a critical role in regulation of ABO blood group antigen. Numerous miRNAs which were up- or downregulated in RBCs of blood group O and of heterozygous genotypes as compared to homozygous genotype possess potential binding sites in the 3'UTR of several transcription factors, such as SP1 and RUNX1. Here we show that silencing of the transcription factor RUNX1 leads to downregulation of blood group A antigen.Methods: We performed knockdown experiments for RUNX1 by lentiviral gene transfer of shRNA in primary hematopoietic stem cells (HSCs) and analyzed blood group A-antigen expression using different method, including flow cytometry, western blot and qPCR.Result: Knockdown of RUNX1 in HSCs leads to a 10-20% reduction of blood group A positive erythroid cells and a 30-40% reduction of blood group A antigens per cell in differentiated RBCs. Furthermore, microarray analysis showed a significant increase of miR-215-5p and miR-192-5p in RBCs of blood group O as compared to homozygous genotype. RUNX1 is known to be a target gene for these miRNAs.Conclusion: Glycosyltransferase A and B expression is regulated by different miRNAs, via simultaneously targeting of the transcription factors SP1 and Runx1 and glycosyltransferase A and B mRNA. The knowledge of the role of microRNAs and the transcription factors SP1 and RUNX1 in the expression of blood group antigens may be extended to other blood groups (Rhesus, Kell, Duffy) and may open the door for therapeutic interventions in diseases where blood group receptors promote disease pathology. DisclosuresNo relevant conflicts of interest to declare.

The role of miR-492 in the regulation of OK blood group antigen expression on red blood cells

To investigate whether miR-492 is involved in the post-transcriptional regulation of OK blood group antigen expression on red blood cells. Two 3'-UTR fragments of the BSG gene were synthesized with a chemical method, which respectively encompassed the BSG rs8259 TT or BSG rs8259 AA sites. The fragments were added with Xho I and Not I restriction enzyme cutting sites at both ends and cloned into a pUC57 vector, which in turn was constructed into a psiCHECK-2 vector and verified by sequencing. K562 cells were transfected with various combinations of miR-492 mimic and constructed psiCHECK2-BSG-T or psiCHECK2-BSG-A recombinant plasmid. A blank control group was set up. Each transfection experiment was repeated three times. The activity of Renilla reniformis luciferase was determined and normalized with that of firefly luciferase, and detected with a dual-luciferase reporter assay system. The data were subjected to statistical analysis. The sequencing results confirmed that the recombinant psiCHECK2 plasmids containing the BSG rs8259 TT or rs8259 AA sites were constructed successfully. The results of dual-luciferase report gene detection showed that the miR-492 mimic could significantly inhibit psiCHECK2-BSG-T at a concentration over 100 nmol/L. However, it could not inhibit psiCHECK-BSG-A. miR-492 may be involved in the regulation of OK antigen expression on red blood cells with the BSG rs8259 TT genotype.

The effect of AB0 and Rhesus blood grouping systems on oncological outcome in patients undergoing radical nephroureterectomy for upper tract urothelial carcinoma

ObjectivesTo investigate the effect of AB0 and Rhesus factor expression blood group systems on outcomes of upper tract urothelial carcinoma patients treated with radical nephroureterectomy. Patients and methodsWe analyzed data from 271 patients with upper tract urothelial carcinoma who underwent radical nephroureterectomy at 3 German academic institutions. Cox and logistic regression models assessed the association of AB0 blood group antigen and Rhesus factor expression with tumor biologic features and outcomes, respectively. ResultsIn total, 119 patients (43.9%) had blood group antigen A0, 42 patients (15.4%) antigen B0, 15 patients (5.5%) antigen AB, and 95 patients (35.0%) the antigen 00. A total of 231 patients (85.2%) were Rhesus factor positive. The AB0 blood group antigen expression was associated with a higher tumor grade (P = 0.049) and sessile tumor architecture (P = 0.019). Both, AB0 blood group system and Rhesus factor expression, were associated with worse performance status (P = 0.024, and P = 0.003, respectively). In contrast, Rhesus factor expression status was not associated with any clinicopathologic characteristics. Neither the AB0 blood group antigens nor the Rhesus factor was associated with survival. ConclusionAB0 blood group antigens and Rhesus factor expression are not associated with survival. The association of the AB0 blood group antigens with adverse pathological features warrants further validation.

FUT2 non-secretor status is associated with altered susceptibility to symptomatic enterotoxigenic Escherichia coli infection in Bangladeshis

Polymorphisms of the FUT2 gene alters glycan ABO(H) blood group and Lewis antigen expression (commonly known as non-secretor status) in the small intestinal mucosa. Whilst non-secretor status affects 20% of the population worldwide, it has been reported to be present in up to 40% of all Bangladeshis. Furthermore, Bangladeshi children are reportedly more susceptible to symptomatic enterotoxigenic Escherichia coli (ETEC) infection if they are non-secretors. Therefore, in an attempt to identify a non-secretor status genotypic biomarker of altered susceptibility to ETEC infection, we used the 1000 Genomes Project to identify three population related non-synonymous FUT2 single nucleotide polymorphisms (SNPs). We then assessed the genotypic frequency of these SNPs in Bangladeshi children who had been clinically monitored for ETEC infection. One novel missense FUT2 SNP, rs200157007-TT and the earlier established rs601338-AA SNP were shown to be causing non-secretor status, with these SNPs being associated with symptomatic but not asymptomatic ETEC infection. Moreover, rs200157007-TT and rs601338-AA were associated with symptomatic but not asymptomatic ETEC infection irrespective of the child’s Lewis secretor status, suggesting FUT2, the regulator of Lewis and ABO(H) antigens in the intestinal mucosa, could be a host genotypic feature affecting susceptibility to ETEC infection.

Relationships between gastrointestinal microbiota and blood group antigens.

FUT2 is a gene for a fucosyltransferase that encodes expression of ABO blood group antigens found on gastrointestinal mucosa and secretions. We hypothesized that the fecal microbiomes of healthy subjects, with blood group antigens A, B, and O, have differing compositions. We analyzed 33 fecal and blood specimens from healthy subjects for FUT2 genotype, and the fecal microbiome was determined by 454 pyrosequencing. Our data show that being a blood group secretor is associated with less diversity at higher orders of taxonomy; and the presence of blood group A antigens in the secretor subjects are associated with an expansion families of bacteria within the gut. Furthermore, our study confirms the previous findings that secretors and nonsecretors have differing bacterial taxa. This extends the previous findings by demonstrating that the impact of being a nonsecretor is higher than that of individual blood group antigens. Additionally, we demonstrate that both secretor status and blood group antigen expression especially affect the Lachnospiraceae family of bacteria within the gut microbiome, with lower abundances noted in nonsecretors and higher abundances in secretors of various blood groups. We further note specific differences in blood group A-secretors demonstrating that the genus Blautia is lower in the group A-secretors compared with the non-A-secretors and that this reduction is accompanied by higher abundances of members of the Rikenellaceae, Peptostreptococcaceae, Clostridiales, and Turicibacter This study offers a first insight into the relationship between the fecal microbiome and blood group antigens in secretors.

NGS and blood group systems: State of the art and perspectives

Molecular analysis, or genotyping, of genes involved in the expression of blood group antigens has been a standard strategy used in immunohaematology laboratories routinely. For the past ten years, next-generation sequencing (NGS), or second-generation sequencing, has become the reference method in genetics. Extensive study of distinct targets, large genomic regions, and even whole genome is henceforth possible by this approach at minimal cost. Blood group genotyping has thus taken advantage of this technological advent. A few preliminary studies have open the way to NGS in this field by studying one or several genes, in a wide range of samples (donors and patients) by using several different platforms. These works have helped in the identification of both the benefits and limitations of the technology. Other recently published studies have benefited from these preliminary data to improve the methodology, specificity and accuracy of output data. In parallel novel strategies, i.e. third-generation sequencing, which can sequence long DNA regions at the single-molecule level, have emerged and shown promise for the potential resolution of complex rearrangements involving genes of the Rh and MNS blood group systems respectively. As technological and methodological hurdles have been overcome, these approaches may be used in a clinical situation in a near future.

Immunohistochemical and genetic exploration of incompatible A blood group antigen expression in invasive micropapillary breast carcinoma: A case report

IntroductionInvasive Micropapillary Carcinoma (IMPC) of the breast is a relatively rare subtype of invasive ductal carcinoma and represents the most inherently aggressive form. Expression of incompatible blood group A antigen in cancer of type O patients has been reported in several types of cancer, however, the biosynthetic mechanism and the genetic basis remain unclear until today. The aim of the present case report study was to evaluate the expression of incompatible blood group A antigen and to identify the genetic basis of this expression in IMPC of the breast. Material and methodsOne patient blood group O with Invasive Micropapillary Carcinoma was screened at Pathology Department of University Hospital CHU Ibn Rochd, Casablanca. ABH antigens expression was assessed by immunohistochemistry. ABO genotyping was performed by allele specific primers PCR-ASP and Exon 6 of ABO gene was sequenced with Sanger method. ResultsH antigen was expressed in endothelial and epithelial cells of normal tissue. However, H antigen expression was lost in both invasive micropapillary carcinomas. A antigen was expressed in IMPC with approximately 80% of positive cells. Tumor DNA was genotyped as heterozygous A/O. In normal DNA, we identified a single frameshift deletion c.320delA p.(Glu107Glyfs*12), which is removed from tumor DNA. ConclusionOur findings suggest that incompatible A antigen expression in IMPC is due to glycosyltransferase A encoded by an A allele which is derived from O allele with a deletion at the position 320.

Blood Group Antigen Recognition via the Group A Streptococcal M Protein Mediates Host Colonization

ABSTRACTStreptococcus pyogenes (group A streptococcus [GAS]) is responsible for over 500,000 deaths worldwide each year. The highly virulent M1T1 GAS clone is one of the most frequently isolated serotypes from streptococcal pharyngitis and invasive disease. The oral epithelial tract is a niche highly abundant in glycosylated structures, particularly those of the ABO(H) blood group antigen family. Using a high-throughput approach, we determined that a strain representative of the globally disseminated M1T1 GAS clone 5448 interacts with numerous, structurally diverse glycans. Preeminent among GAS virulence factors is the surface-expressed M protein. M1 protein showed high affinity for several terminal galactose blood group antigen structures. Deletion mutagenesis shows that M1 protein mediates glycan binding via its B repeat domains. Association of M1T1 GAS with oral epithelial cells varied significantly as a result of phenotypic differences in blood group antigen expression, with significantly higher adherence to those cells expressing H antigen structures compared to cells expressing A, B, or AB antigen structures. These data suggest a novel mechanism for GAS attachment to host cells and propose a link between host blood group antigen expression and M1T1 GAS colonization.

SMIM1 variants rs1175550 and rs143702418 independently modulate Vel blood group antigen expression

The Vel blood group antigen is expressed on the red blood cells of most individuals. Recently, we described that homozygosity for inactivating mutations in SMIM1 defines the rare Vel-negative phenotype. Still, Vel-positive individuals show great variability in Vel antigen expression, creating a risk for Vel blood typing errors and transfusion reactions. We fine-mapped the regulatory region located in SMIM1 intron 2 in Swedish blood donors, and observed a strong correlation between expression and rs1175550 as well as with a previously unreported tri-nucleotide insertion (rs143702418; C > CGCA). While the two variants are tightly linked in Caucasians, we separated their effects in African Americans, and found that rs1175550G and to a lesser extent rs143702418C independently increase SMIM1 and Vel antigen expression. Gel shift and luciferase assays indicate that both variants are transcriptionally active, and we identified binding of the transcription factor TAL1 as a potential mediator of the increased expression associated with rs1175550G. Our results provide insight into the regulatory logic of Vel antigen expression, and extend the set of markers for genetic Vel blood group typing.

Downregulation of Glycosyltransferase a Expression By miRNA-331-3p Is Mediated By the Inhibition of the Transcription Factor SP1

More than 100 ABO subgroup-related variations were detected in the coding region of glycosyltransferases, which may be causative for a weak blood group antigen A or B expression. Most variation in expression is explained genetically by mutations that reduce transferase activity. However, a substantial number of weak variants have not yet been explained by current methods. We recently postulated a role of miRNA in the regulation of blood group A antigen expression levels. By using different approaches, including gene array analysis, luciferase reporter assay and overexpression of glycosyltransferase specific miRNAs in primary hematopoietic stem cells (HSCs), we found that miR-331-3p directly targets glycosyltransferase A and B mRNA. Now we have been further embarking on the underlying mechanisms of miRNA and glycosyltransferase interactions and show that the effects of miR-331-3p are mediated by inhibition of transcription factor SP1, which is a major regulator of the ABO gene, thereby resulting in downregulation of blood group A antigen expression in A2O individuals by up to 80% and in A1O individuals by up to 50%. Using microRNA target prediction tools we also identified Sp1 as a potential target gene for miR-331-3p. Western blot analyses of glycosyltransferase protein expression showed that overexpression of miR-331 led to a decreased glycosyltransferase and SP1 protein expression. Further approaches with the SP1 inhibitor, mithramycin A, revealed similar results. Analysis of Aw04/O1v genotypes revealed elevated miRNA levels, thus confirming microRNAs as regulators of blood group glycosyltransferase expression. Our findings extend our understanding of blood group regulation in carriers of weak blood group variants. Involvement of miRNAs in the downregulation of ABO blood group antigen expression may also provide an explanation for observed changes of ABO antigen expression in abnormal processes such as tumorigenesis, pregnancy and aging. Furthermore, this pathway may play a role in the regulation of other blood group variants (for instance Rhesus, KELL, amongst others). DisclosuresNo relevant conflicts of interest to declare.