Molecular basis for para-Bombay phenotypes in Chinese persons, including a novel nonfunctional FUT1 allele

Two novel alleles on Fucosyltransferase 2 from northern Thai para-Bombay family and computational prediction on mutation effect

BACKGROUND

Major characteristics of the para-Bombay phenotype are the absence of ABH antigens on red blood cells due to fucosyltransferase 1 (FUT1) gene mutation and the presence of these antigens in body secretions due to the active fucosyltransferase 2 (FUT2) gene. An ABO blood group discrepancy can be identified via serological testing, and additional tests can be performed for confirmation. This study aimed to resolve the ABO discrepancy and report two novel alleles on the FUT2 gene in northern Thai para-Bombay families.

STUDY DESIGN AND METHODS

Twelve blood samples were collected from five suspected para-Bombay donors and their families. Nucleotide sequences of ABO, FUT1, and FUT2 were analyzed by polymerase chain reaction-sequence-based typing. Bioinformatics tools were used to predict the effect of suspected novel FUT2 alleles.

RESULTS

All samples exhibited normal ABO alleles, concordant with serological test results. FUT1 exhibited three known variants (c.328G>A, c.424C>T, and c.658C>T). Although FUT2 exhibited two known variants (c.357C>T and c.385A>T), two novel alleles were observed. One allele consisted of c.98A>G, c.101T>G, and c.357C>T with predicted normal transferase activity, whereas the other consisted of c.357C>T and c.617T>C with predicted abnormal enzyme activity.

DISCUSSION

Two novel alleles in FUT2 were reported among the affected para-Bombay individuals of northern Thai families. The c.617T>C variant caused an amino acid change from valine to alanine at position 206, predicted to be an inactive FUT2 enzyme. Inheritance of this variant with the recessive FUT1 allele may lead to inheritance of the rare Bombay blood group in the progeny.

Two novel FUT1 alleles that cause para-Bombay phenotype in a Chinese individual

BACKGROUND

Bombay and para-Bombay phenotypes, which arise from gene mutations of α-1,2-fucosyltransferase FUT1, are very rare in Chinese population. A para-Bombay phenotype Chinese individual with two novel FUT1 mutations was reported here.

STUDY DESIGN AND METHODS

The peripheral blood and saliva samples of the proband and her family members were collected after informed consent. ABO and H blood group phenotyping was performed by haemagglutination methods. ABO genotype was determined by PCR-SSP kit. A, B, and H antigens in saliva were detected by a hemagglutination inhibition test. Fragments encompassing the full coding region of FUT1 and FUT2 genes were PCR amplified and sequenced. Allelic sequences were validated by cloning and sequencing individual colonies.

RESULTS

The serologic reaction results of the proband revealed that A, B, and H antigen were absent on RBCs, but B and H antigen were presented in saliva, and the serum contains anti-H. The proband was assigned as B/O1 by ABO genotyping. Two new heterozygous mutations of FUT1 gene, c.508dupT and c.787A>C, were identified through direct sequencing of PCR-amplified products. TA cloning and sequencing confirmed that two novel mutations were on different alleles. FUT2 gene sequence of the proband is consistent with standard. The other family members of the proband showed normal phenotypes of ABO blood group and their genotypes are consistent with phenotypes.

CONCLUSION

Two novel FUT1 alleles, with the previously not reported mutations c.508dupT and c.787C, respectively, are responsible for the para-Bombay phenotype detected in the sample from the proband.

Aberrant ABO B Phenotype with Irregular Anti-B Caused by a Para-Bombay FUT1 Mutation

Background

Routine ABO blood group typing for pre-transfusion testing of a male Austrian patient of Far Eastern origin showed discrepant results with an apparently weak blood group B phenotype and irregular anti-B.

Materials and Methods

ABH phenotyping and cross-matching was done by standard serologic techniques and levels of H expression were determined by flow cytometry. ABO gene sequencing including regulatory regions as well as analysis of FUT1 (H), FUT2 (Secretor), and FUT3 (Lewis) were carried out.

Results

While monoclonal ABO antigen typing indicated blood group O, weak agglutination reactions using polyclonal human anti-B and anti-AB were seen. In reverse typing at room temperature, the plasma was reactive with A1 and A2 RBCs and negative with B and O cells, whereas at 4°C, anti-B reactivity was found. The indirect anti-globulin cross-match of the patient's plasma was positive with group B RBCs and negative with group O RBCs. Sequencing analysis showed the presence of ABO*B.01 (B114) allele and homozygosity for the FUT1 mutation c.551_552delAG. Flow cytometry demonstrated trace amounts of H antigen on the patient's RBCs.

Conclusion

While a functional B allele was found, analysis of FUT1 and FUT2 genes revealed the presence of a rare para-Bombay genotype O_h^B. Interestingly, no anti-H but irregular anti-B was found in the patient's plasma, responsible for the positive cross-match with group B RBCs. Even though very rare and not reported for the European population, the presence of an H-deficient phenotype should be considered when investigating individuals with an unusual ABO blood group type.

The First Case of Para-Bombay Blood Type Encountered in a Korean Tertiary Hospital

Para-Bombay phenotypes are rare blood groups that have inherent defects in producing H antigens associated with FUT1 and/or FUT2. We report the first case of para-Bombay blood type in a Southeast Asian patient admitted at a tertiary hospital in Korea. A 23-year-old Indonesian man presented to the hospital with fever and was diagnosed with a disseminated nontuberculous mycobacterium infection and anemia. During blood group typing for blood transfusion, cell typing showed no agglutination with both anti-A and anti-B reagents. Serum typing showed strong reactivity against B cells and trace agglutination pattern with A1 cells. His red blood cells failed to react with anti-H reagents. Direct sequencing of FUT1 and FUT2 revealed a missense variation, c.328G>A (p.Ala110Thr, rs56342683, FUT1*01W.02), and a synonymous variant, c.390C>T (p.Asn130=, rs281377, Se357), respectively. This highlights the need for both forward and reverse grouping.

Mutational Analysis of Bombay Phenotype in Iranian People: Identification of a Novel FUT1 Allele

Bombay phenotype is characterized by lack of ABH antigens on RBCs and in body secretions as a result of mutations in fucosyltransferase 1 (FUT1) and fucosyltransferase 2 (FUT2) genes. The aim of this study was a mutational analysis in Iranians with this phenotype. Serological analyses including ABH and adsorption-elution tests were performed in five unrelated Bombay individuals. ABO genotyping was determined by direct sequencing. The coding regions of FUT1 and FUT2 genes were amplified and sequenced directly or after cloning into suitable vector. A novel missense FUT1 allele was detected (G1051T; G351C). Also four reported FUT1 alleles were revealed. Molecular analysis of FUT2 gene confirmed nonsecretor status in all individuals. This and our previous findings suggest the diversity and population specificity of FUT1 alleles.

Molecular basis of Bombay phenotype in Mashhad, Iran: identification of a novel FUT1 deletion

BACKGROUND AND OBJECTIVES

Bombay phenotype is characterized by the lack of H substance both on red blood cell (RBC) surface and in body secretions. Mutations of fucosyltransferase 1 (FUT1) and fucosyltransferase 2 (FUT2) genes are resulted in this rare phenotype.

MATERIALS AND METHODS

Five unrelated patients were tested by hemagglutination and adsorption/elution techniques for the presence of ABH antigens. The saliva specimens were analysed by hemagglutination inhibition method. The exons 6 and 7 of ABO gene were sequenced to determine ABO genotype. The coding fragments of FUT1 and FUT2 were amplified and sequenced by specific primers.

RESULTS

Serologic investigation confirmed Bombay phenotype in all individuals. FUT1 molecular analysis revealed a novel large deletion. Also two novel homozygous mutations were detected; one was a missense mutation (392T>C, L131P) and the other a three nucleotide deletion (668_670delACT, Y224del). FUT2 sequencing showed one reported null allele (428G>A, W143X) and one homozygous deletion of FUT2.

CONCLUSION

Although FUT2 deletion has been reported, this is the first report of FUT1 deletion. Finding two FUT1 novel alleles in Iranian people is indicative of mutation diversity in this gene.

Molecular genetic analysis of the Jk(a-b-) phenotype in Chinese: A novel silent recessive JK allele

The Jk(a-b-) phenotype, referred to as Jknull, is rare in most populations. This blood type is characterized by the absence of Kidd glycoprotein on the surface of red blood cells (RBCs) and moderately reduced ability to concentrate urine. The molecular basis for Jknull phenotype includes splice-site mutations, missense mutations, and a partial gene deletion in the JK(SLC14A1) gene that encodes the human urea transporter protein. In this study, we have analyzed 10 Chinese Jknull samples to determine their molecular bases. In addition to the well known Polynesian Jknull allele, three Jknull alleles were detected including one novel Jknull allele: JKA (130A, 220G).

Genomic analysis of para-Bombay individuals in south-eastern China: the possibility of linkage and disequilibrium between FUT1 and FUT2

BACKGROUND

The para-Bombay phenotype results from a variety of mutations in the α-(1,2)-fucosyltransferase gene (FUT1). We investigated samples from seven Chinese probands serologically typed as having the para-Bombay phenotype.

MATERIALS AND METHODS

The para-Bombay phenotype was identified by standard serological methods. Genetic mutations of FUT1 and FUT2 genes were analysed by DNA sequencing. Heterozygous mutations of FUT1 were identified by TOPO cloning sequencing. Blood samples from 331 randomly-selected Chinese donors were analysed with the SNaPshot system to distinguish five known mutations (Se C357T, A385T, G428A, G716A and FUT1 880delTT) in the FUT1 and FUT2 genes. The genetic characteristics of all para-Bombay probands identified in the Fujian Blood Centre, including those in the present study, were also summarised.

RESULTS

Three FUT1 genotypes, h1/h1 (5 individuals), h1/h6 (1 individual) and h3/h2 (1 individual), and three FUT2 genotypes, Se(357)/Se(357) (5 individuals), Se(357)/Se(357, 385) (1 individual) and Se(357)/Se(357, 716) (1 individual) were observed in seven para-Bombay probands. Among 331 donors, only one individual carried the G716A and 880delTT mutations in heterozygosity; this subjects FUT1 and FUT2 genotypes were H/h2 and Se(357)/Se(357, 716), respectively.

CONCLUSION

The review of all para-Bombay probands identified in the Fujian Blood Centre showed that h1 and h2 are the predominant non-functional FUT1 alleles in Fujian para-Bombay individuals. Our data confirm the hypothesis that the h2 allele is linked to Se(357, 716), and the concurrence of unique FUT1 and FUT2 mutations is geographically specific.

Two Novel α 1,2-Fucosyltransferase Alleles in an H-Deficient Phenotype Individual

BACKGROUND

Abnormal α1,2-fucosyltransferase activity due to gene mutation results in decreased synthesis of H antigen and leads to an H-deficient phenotype. Here we studied the underlying molecular mechanisms in 7 Chinese blood donors with the H-deficient phenotype.

METHODS

Red blood cell typing was performed using standard serologic tests, and ABO genotype was analyzed using ABO polymerase chain reaction with sequence-specific primer tests. The coding sequence of the FUT1 gene was amplified using the specific primers. The FUT1 alleles were identified by a pCRII-TOPO carrier for TOPO TA cloning sequencing.

RESULTS

The H-deficient phenotype frequency was estimated to be approximately 1/30,000 (6/159,515) in the Chinese Han population. The FUT1 gene mutation was demonstrated in 6 Chinese blood donors with the H-deficient phenotype. In only 1 case, no mutation was detected. Novel FUT1 alleles were found in 1 donor. One of these novel FUT1 alleles showed nucleotide 35C>T and 748C>T site mutations that resulted in amino acid substitution of Ala to Val and Trp to Arg at positions 11 and 250, respectively. Another novel FUT1 allele had a nucleotide 655G>C site mutation, causing amino acid substitution of Leu to Val at position 219.

CONCLUSIONS

Two novel FUT1 alleles, 35T+748T and 655C, were identified that may greatly diminish the activity of α1,2-fucosyltransferase and result in the H-deficient phenotype.

The summary of FUT1 and FUT2 genotyping analysis in Chinese para-Bombay individuals including additional nine probands from Guangzhou in China

BACKGROUND

The para-Bombay phenotype is characterized by the absence or weak expression of ABH antigens on the surface of red blood cells, but normal expression in saliva.

STUDY DESIGN AND METHODS

The para-Bombay phenotype of the nine Chinese probands was identified by standard serologic techniques. The coding regions of FUT1 and FUT2 genes were amplified by polymerase chain reaction and then directly sequenced. ABO genotyping was performed by polymerase chain reaction with sequence-specific priming method. The FUT1 and FUT2 genotypes and the distribution in all reported Chinese para-Bombay individuals including our study were also summarized.

RESULTS

Five FUT1 genotypes, h1h3 (n = 3), h1h2 (n = 3), h1h1 (n = 1), h3h3 (n = 1), and h2h3 (n = 1), and three functional FUT2 genotypes, Se(357) Se(357) (n = 4), Se(357) Se(357, 716) (n = 4), and Se(357) Se(357, 385) (n = 1) described before were identified in nine probands.

CONCLUSIONS

The review of the literature shows that a total of 17 FUT1 alleles and four FUT2 alleles (Se(357), Se(357,716), Se(357 385), Se) have been identified in Chinese para-Bombay individuals. The four FUT1 alleles, h1 (547delAG), h2 (880delTT), h3 (C658T), and h4 (C35T; A980C) are most prevalent, which account for more than 90% of all allele counts and are essential to be involved when developing para-Bombay genotyping kit for Chinese.

A novel FUT1 allele was identified in a Chinese individual with para-Bombay phenotype

BACKGROUND

The para-Bombay phenotype is characterised by H-deficient or H partially deficient red blood cells (RBCs) in individuals who secrete ABH antigens in their saliva. Samples from an individual whose RBCs had an apparent para-Bombay phenotype and his family members were investigated and a novel FUT1 allele was identified.

MATERIALS AND METHODS

RBCs' phenotype was characterised by standard serologic technique. Genomic DNA was sequenced with primers that amplified the coding sequence of FUT1 and FUT2, respectively. Routine ABO genotyping analysis was performed. Haplotypes of FUT1 were identified by TOPO cloning sequencing. Recombination expression vectors of FUT1 mutation alleles were constructed and transfected into COS-7 cells. The pα-(1,2)-fucosyltransferase activity of expression protein was determined.

RESULTS

B101/O02 genotype of the proband was correlated with ABH substances in saliva. The proband carried a new FUT1 allele which showed 35C/T, 235G/C and 682A/G heterozygote by directly DNA sequencing. Two haplotypes, 235C and 35T+682G, were identified by TOPO cloning sequencing and COS-7 cells transfected with five recombination vectors including wild-type, 35T, 235C, 682G and 35T+682G alleles were established respectively. The α-(1,2)-fucosyltransferase activities of cell lysates which had transfected with 35T, 235C, 682G and 35T+682G recombination vectors showed 79·45, 16·23, 80·32 and 24·59%, respectively, compared with that of the wild-type FUT1-transfected cell lysates.

CONCLUSION

A novel FUT1 allele 235C was identified, which greatly diminished the activity of α-(1,2)-fucosyltransferase.

Generation of human induced pluripotent stem cells from a Bombay individual: moving towards "universal-donor" red blood cells

Bombay phenotype is one of the rare phenotypes in the ABO blood group system that fails to express ABH antigens on red blood cells. Nonsense or missense mutations in fucosyltransfrase1 (FUT1) and fucosyltransfrase2 (FUT2) genes are known to create this phenotype. This blood group is compatible with all other blood groups as a donor, as it does not express the H antigen on the red blood cells. In this study, we describe the establishment of human induced pluripotent stem cells (iPSCs) from the dermal fibroblasts of a Bombay blood-type individual by the ectopic expression of established transcription factors Klf4, Oct4, Sox2, and c-Myc. Sequence analyses of fibroblasts and iPSCs revealed a nonsense mutation 826C to T (276 Gln to Ter) in the FUT1 gene and a missense mutation 739G to A (247 Gly to Ser) in the FUT2 gene in the Bombay phenotype under study. The established iPSCs resemble human embryonic stem cells in morphology, passaging, surface and pluripotency markers, normal karyotype, gene expression, DNA methylation of critical pluripotency genes, and in-vitro differentiation. The directed differentiation of the iPSCs into hematopoietic lineage cells displayed increased expression of the hematopoietic lineage markers such as CD34, CD133, RUNX1, KDR, alpha-globulin, and gamma-globulin. Such specific stem cells provide an unprecedented opportunity to produce a universal blood group donor, in-vitro, thus enabling cellular replacement therapies, once the safety issue is resolved.

Distribution of ABO blood group allele and identification of three novel alleles in the Chinese Han population

BACKGROUND

The ABO blood group system is clinically important in blood transfusion. The molecular characterization of ABO blood group has clinical and anthropological importance. Here, we determined the ABO alleles distribution and identified three novel alleles in the Chinese Han population.

STUDY DESIGN AND METHODS

Four hundred and seventeen Chinese Han individuals were determined by standard serologic techniques for the ABO blood group phenotypes. The ABO genotypes and alleles were analysed by polymerase chain reaction sequence-based typing (PCR-SBT) for sequencing exon 6 to 7 of the ABO gene. The polymorphisms of intron 5 and 6 of the ABO gene were also analysed by PCR-SBT. The two haplotypes including new alleles were separated by a Dynabeads M-270 Streptavidin protocol.

RESULTS

All ABO genotypes of the samples were consistent with the phenotypes. Fourteen alleles were identified based on the nucleotide sequences of exon 6 and 7, with five common alleles (A101, A102, B101, O01 and O02), six known rare alleles (A205, B110, O04, O05, O07 and O50) and three novel alleles (B112, CisAB06 and 061). The three new alleles appeared with the frequencies of 0.12%, 0.12% and 0.36%, respectively.

CONCLUSION

The detailed frequencies distribution of ABO alleles was studied in the Chinese Han population. We identified 14 alleles, including 3 novel alleles.

Use of maternal plasma for non-invasive prenatal diagnosis of fetal ABO genotypes

BACKGROUND

Measurement of free fetal DNA in maternal plasma opened a door for non-invasive prenatal diagnosis. Prenatal diagnosis of fetal ABO genotypes can provide a basis for the prevention and therapy of maternal-fetal incompatibility. We identified fetal ABO genotypes using fetal DNA in plasma from pregnant women with blood group O. The aim of the study was to investigate the accuracy and feasibility of this method.

METHODS

A total of 105 blood group O women in middle or late pregnancy were enrolled. Fetal DNA in maternal plasma and genomic DNA in umbilical vein blood from newborns were extracted using a QIAamp DNA Blood Kit. DNA was amplified to identify ABO genotypes by PCR with sequence-specific primers (PCR-SSP). The genotype results were evaluated using serologic tests for ABO phenotyping.

RESULTS

Using DNA from umbilical vein blood, ABO genotypes of 105 newborns were successfully identified by PCR-SSP. Using fetal DNA from maternal plasma, 88.6% (93/105) fetal ABO genotypes was correct; 12 false results were from 66 pregnant women with fetuses of type non-O. The accuracy in middle pregnancy was lower than that in late pregnancy, although the difference was not significant (0.05<p<0.10).

CONCLUSIONS

It is feasible to use measurement of fetal DNA in plasma from pregnant women with blood group O for prenatal diagnosis of fetal ABO genotypes. The method is useful for the diagnosis and therapy of ABO maternal-fetal incompatibility and hemolytic disease of the newborn.