Serology and molecular genetic analysis of two unrelated individuals with the same novel CisAB blood type.

OBJECTIVE: This study aims to report two unrelated individuals with the same novel CisAB blood type and confirm this rare blood type using a comprehensive approach that combines serological and molecular biology techniques. METHODS: Peripheral blood samples were collected from two patients and their family members. ABO blood typing and antibody detection were performed using conventional tube methods. Molecular biology techniques were employed to amplify and sequence the 6th and 7th exons of the ABO gene, with reference to gene mutation databases provided by NCBI and ISBT. RESULTS: The genotypes of the two unrelated individuals were identical and were confirmed as a new genotype through ISBT gene database comparison. Serological testing results showed different antigen reaction patterns, especially in terms of reverse typing. Gene sequencing identified a series of mutation points, and both unrelated individuals and one of their daughters had mutations at 297 A>G, 526 C>G, 657 C>T, 703 G>A, 803 G>C, and 930 G>A. According to the comprehensive results from The Blood Group Antigen Gene Mutation Database provided by NCBI, the genotype was determined as Bw37. However, based on the results from Names for ABO (ISBT 001) blood group alleles v1.1 171023, the sequencing results indicated a novel mutation combination not found in the ISBT database. Considering the serological reactions of all three individuals, the final determination was CisAB. CONCLUSIONS: This study confirmed the novel CisAB blood type in two individuals through the comprehensive application of serology and molecular biology techniques. The identified gene mutation points were not recorded in known databases, emphasizing the uniqueness of CisAB blood types. This research provides important insights into the genetic basis of ABO subtypes and the characteristics of CisAB blood types, and the relevant results have been submitted to the ISBT website for further research.

Review of ABO Expression and Variations based on Transcriptional Regulation of the ABO Blood Group Gene.

Background and Summary: We review the transcriptional regulation of ABO expression and discuss variants in the promoter and erythroid cell-specific regulatory region in individuals with weak ABO phenotypes such as Bm, Am, B3, and A3. We also review the molecular mechanisms responsible for variations in ABO expression in development and disease including the cell type-specific expression of ABO during erythroid cell differentiation, and reduction of A- or B-antigens in cancer cells or on red blood cells in patients with leukemia. Although the relationship between ABO blood group antigens and diseases has been characterized, the physiological significance of the ABO blood group system remains unclear. Key Messages: This review discusses accumulated knowledge of the ABO gene regulation and potential reasons for conservation of ABO during evolution.

Association of ABO polymorphisms and pancreatic Cancer/ Cardiocerebrovascular disease: a meta-analysis.

BACKGROUND: ABO gene polymorphisms have been reported to be associated with the risk of multiple cancers and cardiocerebrovascular diseases. However, the results remained controversial. In this study, we conducted a systematic review and meta-analysis to clarify the association between two SNPs (rs505922 and rs657152) in ABO gene and cancers/cardiocerebrovascular diseases. METHOD: All eligible case-control studies come from PubMed, Embase and Web of Science up to Jan. 1, 2019. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the corresponding associations. Sensitivity analysis, publication bias assessment, and heterogeneity test were performed using STATA 12.0. RESULTS: A total of nineteen articles involving twenty-two case-control populations were included according to inclusion and exclusion criteria. Twelve populations (20,820 cases and 27,837 controls) were used to evaluate the relationship between rs505922 and overall cancers and nine populations (22,275 cases and 71,549 controls) were included to assess the association between rs505922 and cardiocerebrovascular diseases. The results showed a significant association between the rs505922 polymorphism and cancers (CvsT: OR = 1.13, 95%CI = 1.05-1.22, P = 0.001), and cardiocerebrovascular diseases (OR = 1.36, 95%CI = 1.19-1.57, P < 0.001). Five populations (8660 cases and 10,618 controls) were included to evaluate association between rs657152 and cancers and five populations (8105 cases and 6712 controls) were included to estimate the relationship between rs657152 and cardiocerebrovascular diseases. The result of meta-analysis reveals that rs657152 was significantly associated with cancers (OR = 1.18, 95%CI = 1.13-1.23, P < 0.001) and cardiocerebrovascular diseases (OR = 1.54, 95%CI = 1.24-1.92, P < 0.001). CONCLUSION: Our study suggested that ABO polymorphisms might serve as a risk factor of pancreatic cancers and cardiocerebrovascular diseases.

Higher DNA methylation of ABO gene promoter is associated with acute myocardial infarction in a hospital-based population in Karachi.

OBJECTIVE: To find out if there is any relationship of methylation status of ABO gene promoter with the risk of acute myocardial infarction (AMI) in a hospital-based Pakistani population in Karachi, Pakistan. METHODS: A case control study comprising of 39 adult AMI patients (both males and females; age range 30-70 years) and 39 normal healthy controls (both males and females and similar age range) nested in a large study (to see the relationship of ABO genotypes with AMI) was designed to investigate the methylation status of ABO gene promoter and its association with AMI. The study was carried out at the Aga Khan University, Karachi during July 2018 to June 2019. DNA isolated from samples of AMI patients and normal healthy controls were converted into bisulphite DNA using a kit method. Methylation specific polymerase chain reaction was carried out to determine the methylation status of ABO gene promoter in both cases and controls. Logistic regression was used to find out any association between increased methylation status of ABO gene promoter and risk of AMI. RESULTS: A significantly higher percentage of DNA methylation of the ABO gene promoter was observed in AMI patients as compared to normal healthy controls (82.1% vs. 35.9%; p value <0.001). This higher methylation status of ABO gene promoter was associated with AMI and the odds of AMI in this population were more than 6-fold in subjects with methylated gene promoter compared to those with unmethylated gene promoter after adjusting with age and waist circumference [AOR (95% CI) = 6.27 (1.76-22.3); p value = 0.005]. CONCLUSION: The ABO gene promoter's hypermethylation appears to be increasing the risk of AMI in a hospital-based Pakistani population in Karachi, Pakistan.

The B allele with a 5·8 kb deletion in intron 1 of the ABO gene is the major allele in Japanese individuals with Bm and A1 Bm phenotypes.

Bm and A1 Bm phenotypes are the most frequent ABO variants in the Japanese population. The B antigen on Bm red blood cells is only detectable by adsorption and elution tests, and plasma B-transferase activity is usually detected at half or less levels compared with that of common B. Recently, a B allele lacking an erythroid cell-specific transcription enhancer in intron 1 of the ABO gene was identified from individuals with Bm and A1 Bm phenotypes, which could explain the unique serologic properties of Bm . In the Japanese Red Cross Society, eight Blood Centers tested blood samples from donors throughout Japan and collected blood samples from 888 Bm and 415 A1 Bm individuals. DNA analysis revealed that 1300 of 1303 (99·77%) individuals had the B allele with a 5·8 kb deletion (c.28 + 5110_10889del), which included the enhancer element.

Association study of polymorphisms in the ABO gene and their gene-gene interactions with ischemic stroke in Chinese population.

AIMS: To investigate the impact of 4 single nucleotide polymorphisms (SNPs) within ABO gene and their gene-gene interactions on ischemic stroke (IS) susceptibility in Chinese Han population. METHODS: A total of 1993 participants (1375 males, 618 females) were selected, including 991 IS patients and 1002 normal controls. The SNPstats (http://bioinfo.iconcologia.net/SNPstats) was used for Hardy-Weinberg equilibrium (HWE) test. Generalized multifactor dimensionality reduction (GMDR) was used to screen the best interaction combination among 4 SNPs within ABO gene. Logistic regression was performed to calculate the ORs (95%CI) for interaction between SNPs. RESULTS: Both rs579459 and rs505922 within ABO gene were associated with IS risk in additive and dominant models. IS risks were higher in those with minor alleles of rs579459 and rs505922 than those with wild-type homozygotes, OR (95%CI) were 1.62 (1.19-2.10) and 1.69 (1.23-2.18), respectively. We did not find any relation of rs651007 and rs529565 with IS risk in both additive and dominant models. GMDR model indicated a significant two-locus model (P = .0010) involving rs505922 and rs579459, indicating a potential interaction between rs505922 and rs579459, the cross-validation consistency of the two-locus models was 9/10, and the testing accuracy was 60.72%. We also found that participants with rs505922- TC/CC and rs579459- TC/CC genotype have the highest IS risk, compared to participants with rs505922- TT and rs579459- TT genotype, OR (95%CI) was 2.94 (1.28-4.66). CONCLUSIONS: We found that rs579459 and rs505922 within ABO gene and their interaction were both associated with increased IS risk in Chinese population.

The potential association of the transcription levels of the ABO gene with the disease phases in AML patients.

Patients with AML may show ABO blood typing discrepancy, and the expression levels of the ABO antigens may show some alterations with the disease progression. To better understand this phenomenon, the blood samples of 25 AML patients and 25 healthy blood donors were examined. The serological ABO blood types of the patients were determined in different AML stages, and gene sequencing was performed to identify the precise ABO genotypes. Reverse transcription-polymerase chain reaction (RT-PCR) was carried out to detect the transcription levels of the antigens. The genotyping result showed that there were 4 patients with genotype A1O, 5 patients with B1O, and 16 patients with A1B1. RT-PCR results indicated that the transcription levels of the ABO gene in 76% (19/25) of the patients were significantly lower compared with those in controls (p <0.05). After therapy, 3/4 patients with A1O returned to normal A, 4/5 patients with B1O returned to normal B, and 10/16 patients with A1B1 returned to normal AB. The patients who achieved complete remission (CR) showed no difference of transcription levels of the ABO gene from those of controls. The data indicated that the transcription levels of the ABO gene changed with the disease progression, suggesting its potential role in the progression of AML disease.

Blood group B gene is barely expressed in in vitro erythroid culture of Bm-derived CD34+ cells without an erythroid cell-specific regulatory element.

BACKGROUND AND OBJECTIVES: Previously, a weak phenotype Am or Bm was assumed to be caused by a reduction of A or B gene expression in bone marrow cells, but not in mucus-secreting cells. However, ABO expression has not been examined in erythroid progenitor cells of Am or Bm individuals. MATERIALS AND METHODS: We carried out in vitro erythroid differentiation of CD34(+) cells from peripheral blood of a Bm individual harbouring a 3.0-kb deletion including an erythroid cell-specific regulatory element, named the +5.8-kb site, in intron 1 of the human ABO blood group gene. RESULTS: During the in vitro differentiation of CD34(+) cells from this Bm individual into erythroid cells, B-antigens were not detectable on the cultured cells by flow cytometric analysis, and allele-specific RT-PCR consistently detected the transcripts from the O allele, but not from the B allele. Moreover, chromatin immunoprecipitation assay demonstrated that both RUNX1 and GATA-2 or GATA-1 were bound to the +5.8-kb site in cultured erythroid cells expressing ABO. CONCLUSION: It is likely that the +5.8-kb site enhances transcription from the ABO promoter in erythroid cells through binding of RUNX1 and GATA-2 or GATA-1.

A 3.0-kb deletion including an erythroid cell-specific regulatory element in intron 1 of the ABO blood group gene in an individual with the Bm phenotype.

We developed a sequence-specific primer PCR (SSP-PCR) for detection of a 5.8-kb deletion (B(m) 5.8) involving an erythroid cell-specific regulatory element in intron 1 of the ABO blood group gene. Using this SSP-PCR, we performed genetic analysis of 382 individuals with Bm or ABm. The 5.8-kb deletion was found in 380 individuals, and disruption of the GATA motif in the regulatory element was found in one individual. Furthermore, a novel 3.0-kb deletion involving the element (B(m) 3.0) was demonstrated in the remaining individual. Comparisons of single-nucleotide polymorphisms and microsatellites in intron 1 between B(m) 5.8 and B(m) 3.0 suggested that these deletions occurred independently.

A Novel ABO Gene Variant Leads to Discrepant Results in Forward/Reverse and Molecular Blood Grouping.

BACKGROUND: Discrepant results in antigen and reverse ABO blood typing are often caused by a variant ABO gene. Molecular analysis can help to characterize such variants. Here, we describe the identification of a novel ABO gene variant in a patient with aberrant ABO phenotype and discrepant genotyping results. METHODS: A patient with discrepant results in automated forward and reverse ABO phenotyping was further investigated by serological (gel and tube technique) and molecular (commercial and inhouse PCR-SSP, DNA sequencing) methods. A PCR-SSP system was established to screen the novel mutation in 1,820 blood donors. RESULTS: Standard serological tests confirmed blood group O, however, only anti-B isoagglutinins were present. A monoclonal anti-AB antibody detected very weak agglutination in gel technique. Standard ABO genotyping using PCR-SSP led to discrepant results (O(1)/O(1) or O(1)/A) depending on the test system used. ABO exon re-sequencing identified a novel missense mutation in exon 6 at position 248A>G (Asp83Gly) in the binding region of PCR-SSP primers for the detection of 261G alleles. Blood donors with regular ABO blood groups were all negative for the 248G allele designated Aw34. CONCLUSION: The novel ABO gene variant Aw34 is associated with very weak A antigen expression and absent anti-A isoagglutinins. The mutation is located in exon 6 close to the O(1)-specific 261G deletion in the binding region of PCR-SSP primers. Presumably, depending on the primer concentration used in commercial ABO genotyping kits, the mutation could lead to a false-negative reaction.

Generation of hiPSCs with ABO c.767T>C substitution: resulting in splicing variants.

Introduction: The ABO blood group system has important clinical significance in the safety of blood transfusion and organ transplantation. Numerous ABO variations, especially variations in the splice sites, have been identified to be associated with some ABO subtypes. Methods: Here, we performed the c.767T>C substitution of the ABO gene in human induced pluripotent stem cells (hiPSCs) by the adenosine base editor (ABE) system and described its characteristics at the genome level in detail. Results: The hiPS cell line with c.767T>C substitution maintained a normal karyotype (46, XX), expressed pluripotency markers, and showed the capability to spontaneously differentiate into all three germ layers in vivo. The genome-wide analysis demonstrated that the c.767T>C substitution in the ABO gene did not cause any detected negative effect in hiPSCs at the genome level. The splicing transcript analysis revealed that splicing variants were observed in the hiPSCs with ABO c.767T>C substitutions. Conclusion: All these results indicated that some splicing variants occurred in hiPSCs with c.767 T>C substitution of ABO gene, which probably had a significant effect on the formation of the rare ABO*Ael05/B101 subtype.

COVID-19 host genetics and ABO blood group susceptibility.

Twenty-five susceptibility loci for SARS-CoV-2 infection and/or COVID-19 disease severity have been identified in the human genome by genome-wide association studies, and the most frequently replicated genetic findings for susceptibility are genetic variants at the ABO gene locus on chromosome 9q34.2, which is supported by the association between ABO blood group distribution and COVID-19. The ABO blood group effect appears to influence a variety of disease conditions and pathophysiological mechanisms associated with COVID-19. Transmission models for SARS-CoV-2 combined with observational public health and genome-wide data from patients and controls, as well as receptor binding experiments in cell lines and human samples, indicate that there may be a reduction or slowing of infection events by up to 60% in certain ABO blood group constellations of index and contact person in the early phase of a SARS-CoV-2 outbreak. The strength of the ABO blood group effect on reducing infection rates further depends on the distribution of the ABO blood groups in the respective population and the proportion of blood group O in that population. To understand in detail the effect of ABO blood groups on COVID-19, further studies are needed in relation to different demographic characteristics, but also in relation to recent data on reinfection with new viral variants and in the context of the human microbiome.

[Study on BW.12 Subtype Caused by c.278C>T Mutation in Exon 6 of ABO Gene].

OBJECTIVE: To investigate the effect of ABO gene α-1,3-D galactosyl transferase mutation on B antigen expression and its molecular mechanism. METHODS: The proband and their family members were identified by routine serological methods, and ABO genotyping and sequence analysis were performed by polymerase chain reaction-sequence specificity (PCR-SSP) and direct sequencing of PCR products from exon 1-7 of ABO gene. The 3D structural simulation of mutant proteins was performed by bioinformatics software. The effect of gene mutation on protein structural stability was analyzed. RESULTS: The proband and his family members were subtype B. ABO genotyping indicated that the proband's genotype was Bw12/O. Gene sequencing results confirmed the presence of ABO*BW.12 characteristic variation c.278C>T in the 6th exon of allele B, leading to the replacement of polypeptide chain p.Pro93Leu. The 3D structure simulation analysis of the protein showed that the hydrogen bonds and water molecules connected to the protein changed after amino acid substitution. The family investigation found that the grandfather, father, uncle and brother of the proband all carried the same ABO*BW.12 allele. CONCLUSION: The mutation of the 6th exon c.278C>T of ABO gene led to the substitution of polypeptide chain amino acids, which affected the stability of α-1,3-D galactosyl transferase protein, resulting in the change of enzyme activity, and the Bw.12 phenotype, which can be stably inherited.

Association between polymorphisms in ABO gene and stroke patients with small artery occlusion in southern Chinese Han population.

OBJECTIVE: The purpose of this study was to investigate associations between two single nucleotide polymorphisms (SNPs) rs505922 and rs532436 in ABO gene and the risk of small artery occlusion stroke (SAO) in southern Chinese Han population. METHODS: Our case-control study comprising 121 patients with SAO and 136 controls. All participants were Han population of southern China. IS sub-type was defined on the basis of the TOAST criteria. SAO was strictly diagnosed after a systematic physical examination and neuroimaging via MRI. Genotype analysis was conducted by the snapshot technique. RESULTS: The distribution of rs532436 genotype between these two groups showed a statistically significant difference (P = 0.048) while that of rs505922 genotype showed no significant difference (P = 0.572). SNP rs532436 was significantly associated with SAO in overdominant model (GA vs. GG + AA) after adjusting for age, hypertension history, diabetes history and cigarette smoking (adjusted OR = 2.03, 95% CI: 1.14-3.62, P = 0.016). However, under all genetic models, the rs505922 polymorphism failed to show association with SAO. CONCLUSION: The resultsindicate that rs532436 polymorphism in ABO gene may have association with SAO in southern Chinese Han population.

Genome-wide association study revealed novel candidate gene loci associated with soluble E-selectin levels in a Taiwanese population.

BACKGROUND AND AIMS: Increase soluble E-selectin (sE-selectin) levels are associated with various inflammation and cardiometabolic disorders. METHODS: This study aimed to investigate the genetic determinants of circulating sE-selectin levels by genome-wide association study (GWAS) in 4,525 Taiwan Biobank (TWB) participants and genotype-phenotype association analysis for sE-selectin level-determining alleles in over 80,000 TWB participants. RESULTS: By GWAS, ABO, SELE, and FUT6 gene variants were identified as the determinants of sE-selectin levels, which reach genome-wide significance (maximum p = 3.25 × 10-271, 4.81 × 10-14, and 9.64 × 10-12, respectively). After further adjustment for the lead ABO rs2519093 genotypes, three novel gene loci, EVI5, FER and DMAC1, were associated with sE-selectin levels at p < 5 × 10-7. Three other previously reported gene loci, CELSR2, ST3GAL6-AS1, and HNF1A-AS1, also showed supportive evidence for the association with sE-selectin levels (maximum p < 0.0073). A multivariate analysis revealed age, body mass index, current smoking, hemoglobin A1C, hematocrit, leukocyte and platelet counts, serum alanine aminotransferase, triglycerides, and uric acid levels were independently associated with sE-selectin levels, in which the above ten gene loci contribute to 27.68% of the variance. For genotype-phenotype association analysis, a pleiotropic effect was demonstrated with genome-wide significant association between ABO gene variants and total and low-density-lipoprotein cholesterol levels, leukocyte counts and hematocrit. CONCLUSIONS: Our data provide novel insight into the regulation of sE-selectin levels. These results may open new avenues in understanding the critical role of E-selectin on the pathogenesis of inflammatory and cardiometabolic disorders.

Allelic distribution of ABO gene in Chinese centenarians.

OBJECTIVE: Human ABO blood groups are determined by the alleles A, B, and O (O01 and O02) of the ABO gene and have been linked to the risks for cardiovascular diseases and cancers that affect lifespan.We examined the genetic associations of the ABO gene and blood groups with longevity. METHODS: We inspected the frequencies of the A, B, O, and O02 alleles in a large Chinese centenarian population (n = 2201) and in middle-aged controls (n = 2330). The single nucleotide polymorphisms were selected as allele A (rs507666), B (rs8176743, rs8176746, and rs8176749), O (rs687289), and O02 (rs688976, rs549446, and rs512770). RESULTS: Supported by allelic and genotypic association studies, the frequencies of blood types A, B, O, and AB in centenarian versus control participants were not statistically different: 0.2821 versus 0.2781 (χ2 = 0.09, P = 0.76), 0.2867 versus 0.3060 (χ2 = 2.03, P = 0.15), 0.3380 versus 0.3159 (χ2 = 2.52, P = 0.11), and 0.0859 versus 0.0910 (χ2 = 0.37, P = 0.54), respectively. Sex had little effect on these distributions. CONCLUSION: Integrated with other previous reports, we conclude from this large Chinese cohort that genetic variants of the ABO gene and blood groups are not associated with longevity.

Analysis of ABO gene mRNA expression in peripheral blood of patients with acute myeloid leukemia / 中国输血杂志

【Objective】 To investigate the expression characteristics of ABO gene mRNA in peripheral blood of patients with acute myeloid leukemia. 【Methods】 The RNA-seq data of acute myeloid leukemia in TCGA database and the whole blood RNA-seq data in GTEx database were downloaded. The difference of ABO gene mRNA expression between acute myeloid leukemia and GTEx whole blood samples was analyzed by R software, and the relationship between ABO gene mRNA expression and DNA methylation, immune infiltration and prognosis was analyzed. 【Results】 The expression level of ABO gene mRNA in acute myeloid leukemia(median: 1.333, P25: 3.654, P75: 0.401)was significantly lower than that in the control group(median: 3.576, P25: 3.747, P75: 3.470)(P<0.001). The expression level of ABO gene mRNA in acute myeloid leukemia was negatively correlated with the methylation of + 82(r=-0.249, P<0.001), + 618(r=-0.268, P<0.001), + 1 080(r=-0.105, P<0.001) and + 1 409(r=-0.210, P<0.001) at downstream of transcription start site, and positively correlated with the immune infiltration of nine types of immune cells (B cells, CD8 T cells, Cytotoxic cells, pDC, T cells, T helper cells, Tcm, Tfh and Treg) (P<0.001). There was no significant difference in overall survival between patients with high (median survival time: 366 days, confidence interval: 304-731 days) and low (median survival time: 731 days, confidence interval: 335-1 402 days) expression of ABO gene mRNA in acute myeloid leukemia (P>0.05). 【Conclusion】 The mRNA expression of ABO gene in peripheral blood of patients with acute myeloid leukemia is decreased, which is associated with DNA methylation of the first intron of ABO gene and immune infiltration, but not with the prognosis.

Can 9q34.2 rs633862 polymorphism predict survival in epithelial ovarian cancer?

OBJECTIVE: Our previous genome-wide association study (GWAS) identified that the ABO rs633862 variant in chromosome 9q34.2 was associated with the risk of epithelial ovarian cancer (EOC) in Chinese Han women. The aim of the present study was to evaluate its prognostic effect on EOC. METHODS: A total of 669 EOC patients were enrolled for the genotyping of rs633862 variant in 9q34.2. We used Kaplan-Meier survival curves, univariate and multivariate Cox proportional hazard models to evaluate the association of rs633862 with overall survival (OS) in EOC patients. RESULTS: We found that rs633862 variant AG/GG genotypes were significantly associated with a longer OS by using univariate Cox proportional hazards regression analysis, compared with the rs633862 AA genotype (HR = 0.69, 95% CI [0.49-0.98], p = 0.035), albeit with a boardline significance in the multivariate analysis. Similar findings were observed in the subgroup of high-grade serous ovarian carcinoma. Further expression quantitative trait loci (eQTL) analysis indicated that the rs633862 AA genotype was associated with an increased level of ABO mRNA expression (p = 1.8 × 10-11). CONCLUSIONS: Supplementary to the previous GWAS, our study provides additional evidence on the prognostic value of the 9q34.2 rs633862 variant in EOC patients, and this variant may function by regulating the ABO mRNA expression.