| 1. |
- Clausen, Frederik Banch, et al.
(författare)
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External quality assessment of noninvasive fetal RHD genotyping
- 2020
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Ingår i: Vox Sanguinis. - : Wiley. - 0042-9007 .- 1423-0410. ; 115:5, s. 466-471
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Tidskriftsartikel (refereegranskat)abstract
- Background and objectives: Fetal RHD genotyping of cell-free maternal plasma DNA from RhD negative pregnant women can be used to guide targeted antenatal and postnatal anti-D prophylaxis for the prevention of RhD immunization. To assure the quality of clinical testing, we conducted an external quality assessment workshop with the participation of 31 laboratories. Materials and methods: Aliquots of pooled maternal plasma from gestational week 25 were sent to each laboratory. One sample was fetal RHD positive, and a second sample was fetal RHD negative. A reporting scheme was supplied for data collection, including questions regarding the methodological setup, results and clinical recommendations. The samples were tested blindly. Results: Different methodological approaches were used; 29 laboratories used qPCR and two laboratories used ddPCR, employing a total of eight different combinations of RHD exon targets. Fetal RHD genotyping was performed with no false-negative and no false-positive results. One inconclusive result was reported for the RHD positive sample. All clinical conclusions were satisfactory. Conclusion: This external quality assessment workshop demonstrates that despite the different approaches taken to perform the clinical assays, fetal RHD genotyping is a reliable laboratory assay to guide targeted use of Rh prophylaxis in a clinical setting.
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| 2. |
- Clausen, Frederik Banch, et al.
(författare)
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Recommendation for validation and quality assurance of non-invasive prenatal testing for foetal blood groups and implications for IVD risk classification according to EU regulations
- 2022
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Ingår i: Vox Sanguinis. - : Wiley. - 0042-9007 .- 1423-0410. ; 117:2, s. 157-165
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Forskningsöversikt (refereegranskat)abstract
- Background and Objectives: Non-invasive assays for predicting foetal blood group status in pregnancy serve as valuable clinical tools in the management of pregnancies at risk of detrimental consequences due to blood group antigen incompatibility. To secure clinical applicability, assays for non-invasive prenatal testing of foetal blood groups need to follow strict rules for validation and quality assurance. Here, we present a multi-national position paper with specific recommendations for validation and quality assurance for such assays and discuss their risk classification according to EU regulations. Materials and Methods: We reviewed the literature covering validation for in-vitro diagnostic (IVD) assays in general and for non-invasive foetal RHD genotyping in particular. Recommendations were based on the result of discussions between co-authors. Results: In relation to Annex VIII of the In-Vitro-Diagnostic Medical Device Regulation 2017/746 of the European Parliament and the Council, assays for non-invasive prenatal testing of foetal blood groups are risk class D devices. In our opinion, screening for targeted anti-D prophylaxis for non-immunized RhD negative women should be placed under risk class C. To ensure high quality of non-invasive foetal blood group assays within and beyond the European Union, we present specific recommendations for validation and quality assurance in terms of analytical detection limit, range and linearity, precision, robustness, pre-analytics and use of controls in routine testing. With respect to immunized women, different requirements for validation and IVD risk classification are discussed. Conclusion: These recommendations should be followed to ensure appropriate assay performance and applicability for clinical use of both commercial and in-house assays.
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| 3. |
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| 4. |
- De La Vega Elena, Carlos D., et al.
(författare)
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A rare blood group: p phenotype
- 2009
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Ingår i: Medicina. - 1648-9144. ; 69:6, s. 651-654
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Tidskriftsartikel (refereegranskat)abstract
- A rare blood group: p phenotype. A rare blood group is usually defined as the absence of a high prevalence antigen or the absence of several antigens within a single blood group system. These individuals may develop clinically significant red cell antibodies to the high incidence red cell antigens they lack. A 33-year-old alloimmunized woman was referred to our center at the 12th week of her third pregnancy for evaluation and follow up. The laboratory work-up grouped her as belonging to "p" phenotype, associated with difficulties to find compatible blood for transfusion and a high incidence of recurrent miscarriage. At 36 weeks, a baby girl was born by induced labor due to fetal suffering. With a negative direct antiglobulin test but a positive elution test, she was in the neonatology ward for one week receiving luminotherapy. Homozygosity for a missense mutation at position 752 (c.752C > T) in the A4GALT gene was found to be responsible for the p phenotype. This mutation changes a proline to a leucine at codon 251 of the 4-alpha-galactosyltransferase. Recently, due to an imminent chirurgical intervention and the impossibility to have compatible blood available for transfusion. an autologous donation plan was designed to satisfy probable demand. This case showed the need for blood bank facilities capable to respond satisfactorily to these situations in Argentina. This would facilitate the storage of cryopreserved blood from individuals with rare blood groups for homologous use or to develop rare blood donors programs.
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| 5. |
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| 6. |
- Gassner, Christoph, et al.
(författare)
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International Society of Blood Transfusion Working Party on Red Cell Immunogenetics and Blood Group Terminology Report of Basel and three virtual business meetings : Update on blood group systems
- 2022
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Ingår i: Vox Sanguinis. - : Wiley. - 1423-0410 .- 0042-9007. ; 117:11, s. 1332-1344
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND OBJECTIVES: Under the ISBT, the Working Party (WP) for Red Cell Immunogenetics and Blood Group Terminology is charged with ratifying blood group systems, antigens and alleles. This report presents the outcomes from four WP business meetings, one located in Basel in 2019 and three held as virtual meetings during the COVID-19 pandemic in 2020 and 2021.MATERIALS AND METHODS: As in previous meetings, matters pertaining to blood group antigen nomenclature were discussed. New blood group systems and antigens were approved and named according to the serologic, genetic, biochemical and cell biological evidence presented.RESULTS: Seven new blood group systems, KANNO (defined numerically as ISBT 037), SID (038), CTL2 (039), PEL (040), MAM (041), EMM (042) and ABCC1 (043) were ratified. Two (039 and 043) were de novo discoveries, and the remainder comprised reported antigens where the causal genes were previously unknown. A further 15 blood group antigens were added to the existing blood group systems: MNS (002), RH (004), LU (005), DI (010), SC (013), GE (020), KN (022), JMH (026) and RHAG (030).CONCLUSION: The ISBT now recognizes 378 antigens, of which 345 are clustered within 43 blood group systems while 33 still have an unknown genetic basis. The ongoing discovery of new blood group systems and antigens underscores the diverse and complex biology of the red cell membrane. The WP continues to update the blood group antigen tables and the allele nomenclature tables. These can be found on the ISBT website (http://www.isbtweb.org/working-parties/red-cell-immunogenetics-and-blood-group-terminology/).
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| 7. |
- Hellberg, Åsa, et al.
(författare)
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A novel nonsense variant in RHAG underlies a Nordic Rhnull phenotype
- 2023
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Ingår i: Vox Sanguinis. - : John Wiley & Sons. - 0042-9007 .- 1423-0410. ; 118:8, s. 690-694
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Tidskriftsartikel (refereegranskat)abstract
- Background and ObjectivesThe extremely rare Rhnull phenotype is characterized by the absence of all Rh antigens on erythrocytes. It is divided into the regulator and amorph types based on the underlying genetic background. The more common regulator type depends on critical variants silencing RHAG, which encodes RhAG glycoprotein, necessary for RhD/RhCE expression. Rhnull cells have altered expression of glycophorin B and LW glycoprotein.Materials and MethodsFour unrelated Rhnull individuals were investigated. Serological testing was performed according to standard blood bank practice. RHD/RHCE and S/s allele-specific Polymerase chain reaction (PCR) genotyping was done on genomic DNA using in-house PCR assays. RHAG, and in some cases also RHD/RHCE, were sequenced. Initial s phenotyping results triggered additional serological investigation.ResultsAnti-Rh29 was identified in all four individuals. Extended typing with anti-S and anti-s showed that the three samples predicted to type as s+ failed to react with 2 of 5 anti-s. Sequence analysis of all 10 RHAG exons and the immediate intron/exon boundaries revealed a single nucleotide variant in the 3′-end of intron 6, c.946 −2a>g in all samples. RHD/RHCE showed no alterations.ConclusionA novel Nordic Rhnull allele was identified. In addition, it was shown that s+ Rhnull red blood cells are not only U− but also have qualitative changes in their s antigen expression.
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| 8. |
- Hellberg, Åsa, et al.
(författare)
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A novel RHCE*02 allele, containing the single-nucleotide change c.460A>G, encodes weakened expression of C and e antigens
- 2016
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Ingår i: Transfusion. - : Wiley. - 0041-1132 .- 1537-2995. ; 56:9, s. 2391-2392
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel RHCE*02 allele in a Swedish blood donor that is characterized by the change c.460A>G (Arg154Gly). The blood donor's red blood cells showed variable reactivity with different monoclonal anti-C and anti-e and antigen strength was markedly weakened. We believe that these changes represent both a quantitative and qualitative alteration of the antigens encoded by this allele.
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| 9. |
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| 10. |
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| 11. |
- Hellberg, Åsa, et al.
(författare)
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An update on the GLOB blood group system and collection.
- 2013
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Ingår i: Immunohematology. - 0894-203X. ; 29:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- The P blood group antigen of the GLOB system is a glycolipid structure, also known as globoside, on the red blood cells (RBCs) of almost all individuals worldwide. The P antigen is intimately related to the Pk and NOR antigens discussed in the review about the P1PK blood group system. Naturally occurring anti-P is present in the serum of individuals with the rare globoside-deficient phenotypes p, P1k, and P2k and has been implicated in hemolytic transfusion reactions as well as unfavorable outcomes of pregnancy. The molecular genetic basis of globoside deficiency is absence of functional P synthase as a result of mutations at the B3GALNT1 locus. Other related glycolipid structures, the LKE and PX2 antigens, remain in the GLOB blood group collection pending further evidence about the genes and gene products responsible for their synthesis.
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| 12. |
- Hellberg, Åsa, et al.
(författare)
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Expression of a novel missense mutation found in the A4GALT gene of Amish individuals with the p phenotype.
- 2008
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Ingår i: Transfusion. - : Wiley. - 1537-2995 .- 0041-1132. ; 48:3, s. 479-487
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The rare p phenotype is found at a higher frequency in Amish people than in other populations. Different mutations in the 4-alpha-galactosyltransferase gene (A4GALT), responsible for synthesis of P(k) (Gb(3)) antigen, have been found to cause the P(k)-deficient p phenotype. The aim of this study was to explore the molecular background of the p phenotype in people of Amish origin. STUDY DESIGN AND METHODS: Twenty blood samples with the p phenotype, 19 of them from Amish individuals and 1 Pakistani, were investigated. Amplification of genomic DNA by polymerase chain reaction (PCR) and sequencing by capillary electrophoresis were performed. Blood donors of different geographic origin were screened with PCR-allele-specific primer to investigate whether the novel mutation occurs among individuals with common phenotypes. The mutation was also cloned into an expression vector and transfected to Namalwa cells, which do not normally express P(k). P(k) expression on the transfected cells and P/P(k) on red blood cells (RBCs), both with p and with common phenotypes, were analyzed by flow cytometry. RESULTS: All 20 samples were homozygous for 299C>T changing serine to leucine in a region that is highly conserved in homologous genes across species borders. The mutation was not found in any of the 500 alleles of blood donors investigated. P(k) expression was neither observed by serology and flow cytometry on p RBCs from Amish individuals nor following transfection of cells with constructs containing the novel missense mutation. CONCLUSION: A novel A4GALT missense mutation causes the p phenotype in Amish individuals.
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| 13. |
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| 14. |
- Hellberg, Åsa, et al.
(författare)
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Molecular basis of the globoside-deficient P(k) blood group phenotype. Identification of four inactivating mutations in the UDP-N-acetylgalactosamine: globotriaosylceramide 3-beta-N-acetylgalactosaminyltransferase gene.
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:33, s. 29455-29459
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Tidskriftsartikel (refereegranskat)abstract
- The biochemistry and molecular genetics underlying the related carbohydrate blood group antigens P, P(k), and LKE in the GLOB collection and P1 in the P blood group system are complex and not fully understood. Individuals with the rare but clinically important erythrocyte phenotypes P(1)k and P(2)k lack the capability to synthesize P antigen identified as globoside, the cellular receptor for Parvo-B19 virus and some P-fimbriated Escherichia coli. As in the ABO system, naturally occurring antibodies, anti-P of the IgM and IgG class with hemolytic and cytotoxic capacity, are formed. To define the molecular basis of the P(k) phenotype we analyzed the full coding region of a candidate gene reported in 1998 as a member of the 3-beta-galactosyltransferase family but later shown to possess UDP-N-acetylgalactosamine:globotriaosylceramide 3-beta-N-acetylgalactosaminyltransferase or globoside synthase activity. Homozygosity for different nonsense mutations (C(202) --> T and 538insA) resulting in premature stop codons was found in blood samples from two individuals of the P(2)k phenotype. Two individuals with P(1)k and P(2)k phenotypes were homozygous for missense mutations causing amino acid substitutions (E266A or G271R) in a highly conserved region of the enzymatically active carboxyl-terminal domain in the transferase. We conclude that crucial mutations in the globoside synthase gene cause the P(k) phenotype.
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| 15. |
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| 16. |
- Hellberg, Åsa, et al.
(författare)
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P1PK: the blood group system that changed its name and expanded.
- 2013
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Ingår i: Immunohematology. - 0894-203X. ; 29:1, s. 25-33
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Tidskriftsartikel (refereegranskat)abstract
- The antigens in the P1PK blood group system are carried on glycosphingolipids. The system currently includes three different antigens, P1, Pk, and NOR. The P1 antigen was disovered in 1927 by Landsteiner and Levine, and Pk and NOR were described in 1951 and 1982, respectively. As in the ABO system, naturally occurring antibodies of the immunoglobulin (Ig) M or IgG class, against the missing carbohydrate structures, can be present in the sera of people lacking the corresponding antigen. Anti-P1 is generally a weak and cold-reactive antibody not implicated in hemolytic transfusion reaction (HTR) or hemolytic disease of the fetus and newborn while Pk antibodies can cause HTR, and anti-NOR is regarded as a polyagglutinin. A higher frequency of miscarriage is seen in women with the rare phenotypes p, P1k, and P2k. Furthermore, the Pk and P1 antigens have wide tissue distributions and can act as host receptors for various pathogens and toxins. Why p individuals lack not only Pk and P expression but also P1 has been a longstanding enigma. Recently, it was shown that the same A4GALT-encoded galactosyltransferase synthesizes both the P1 and Pk antigens and that a polymorphism in a new exon in this gene predicts the P1 and P2 phenotypes.
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| 17. |
- Hellberg, Åsa
(författare)
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Studies on the genetic basis of Pk, P and P1 blood group antigen expression
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The clinically important carbohydrate P/GLOB blood group systems and collection give rise to both common (P1, P2) and rare (p, P1k, P2k) blood group phenotypes. The associated antibodies are implicated in severe transfusion reactions and recurrent spontaneous abortions. The aim of this study was to explore the molecular genetic basis of Pk, P and P1 antigen expression. Sequence analysis of the A4GALT and B3GALNT1 genes proposed to synthesize the related Pk (Gb3) and P (Gb4) antigens, respectively, were performed in p and Pk individuals (n=99) of different geographic/ethnic origin. A total of 24 novel mutations were identified, emphasizing the genetic heterogeneity at the glycosyltransferase loci underlying these blood groups. As a result of this study, the P antigen was assigned its own blood group system, GLOB (028), by ISBT. Expression studies in the Pk-negative Namalwa cells transfected with mutated A4GALT-constructs showed Pk expression levels comparable to negative controls. RBCs with p phenotype showed no Pk and P activity while both P and Pk expression on RBCs varied considerably between individuals with common phenotypes. Sixteen polymorphic sites were detected while investigating if polymorphisms in the regulatory region of the A4GALT gene might be the basis for the P1/P2 phenotypes. No clear-cut correlation was found and two previously proposed P2-specific mutations were detected in homozygous form both in P1 and P2 donors indicating that these mutations are not the sole cause of the P1/P2 status. However, the correlation between the A4GALT locus and P2 status seems to be rather strong
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| 18. |
- Hellberg, Åsa, et al.
(författare)
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Two previously proposed P-1/P-2-differentiating and nine novel polymorphisms at the A4GALT (P-k) locus do not correlate with the presence of the P1 blood group antigen
- 2005
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Ingår i: BMC Genetics. - : Springer Science and Business Media LLC. - 1471-2156. ; 6:49
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Tidskriftsartikel (refereegranskat)abstract
- Background: The molecular genetics of the P blood group system and the absence of P1 antigen in the p phenotype are still enigmatic. One theory proposes that the same gene encodes for both the P1 and P-k glycosyltransferases, but no polymorphisms in the coding region of the P-k gene explain the P-1/P-2 phenotypes. We investigated the potential regulatory regions up- and downstream of the A4GALT (P-k) gene exons. Results: P-1 (n = 18) and P-2 (n = 9) samples from donors of mainly Swedish descent were analysed by direct sequencing of PCR-amplified 5'- and 3'-fragments surrounding the P-k coding region. Seventy-eight P-1 and P-2 samples were investigated with PCR using allele-specific primers (ASP) for two polymorphisms previously proposed as P-2-related genetic markers(- 551_-550insC, -160A>G). Haplotype analysis of single nucleotide polymorphisms was also performed with PCR-ASP. In similar to 1.5 kbp of the 3'-untranslated region one new insertion and four new substitutions compared to a GenBank sequence (AL049757) were found. In addition to the polymorphisms at positions - 550 and - 160, one insertion, two deletions and one substitution were found in similar to 1.0 kbp of the 5'-upstream region. All 20 P-2 samples investigated with PCR-ASP were homozygous for -550insC. However, so were 18 of the 58 P-1 samples investigated. Both the 20 P-2 and the 18 P-1 samples were also homozygous for -160G. Conclusion: The proposed P-2-specific polymorphisms, -551_-550insC and -160G, found in P-2 samples in a Japanese study were found here in homozygous form in both P-1 and P-2 donors. Since P-2 is the null allele in the P blood group system it is difficult to envision how these mutations would cause the P-2 phenotype. None of the novel polymorphisms reported in this study correlated with P-1/P-2 status and the P1/p mystery remains unsolved.
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| 19. |
- Hosseini Maaf, Bahram, et al.
(författare)
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ABO exon and intron analysis in individuals with the A(weak)B phenotype reveals a novel O-1v-A(2) hybrid allele that causes four missense mutations in the A transferase
- 2003
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Ingår i: BMC Genetics. - : Springer Science and Business Media LLC. - 1471-2156. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Since the cloning in 1990 of cDNA corresponding to mRNA transcribed at the blood-group ABO locus, polymorphisms due to ethnic and/or phenotypic variations have been reported. Some subgroups have been explained at the molecular level, but unresolved samples are frequently encountered in the reference laboratory. Results: ABO blood grouping discrepancies were investigated serologically and by ABO genotyping [duplex polymerase-chain-reaction (PCR)-restriction-fragment-length-polymorphism (RFLP) and PCR-allele-specific-primer (ASP) across intron 6] and DNA sequencing of the ABO gene and its proposed regulatory elements. Blood samples from five individuals living in Portugal, Switzerland, Sweden and the USA were analysed. These individuals were confirmed to be of Black ethnic origin and had the unusual A(weak)B phenotype but appeared to have the A(2)B genotype without previously reported mutations associated with weak A or B expression. Sequencing of this A allele (having 467C>T and 1061delC associated with the common A(2) [A201] allele) revealed three mutations regularly encountered in the O-1v [O02] allele: 106C>T (Val36Phe), 188G>A (Arg63His), 220C>T (Pro74Ser) in exons 3, 4 and 5, respectively. The additional presence of 46G>A (Ala16Thr) was noted, whilst 189C>T that normally accompanies 188G>A in O-1v was missing, as were all O-1v-related mutations in exons 6 and 7 (261delG, 297A>G, 646T>A, 681G>A, 771C>T and 829G>A). On screening other samples, 46G>A was absent, but two new O alleles were found, a Jordanian O-1 and an African O1v allele having 188G>A but lacking 189C>T. Sequencing of introns 2, 3, 4 and 5 in common alleles (A(1)[A101], A(2), B [B101], O-1, O-1v and O-2 [O03]) revealed 7, 12, 17 and 8 polymorphic positions, respectively, suggesting that alleles could be defined by intronic sequences. These polymorphic sites allowed definition of a breakpoint in intron 5 where the O-1v-related sequence was fused with A(2) to form the new hybrid. Intron 6 has previously been sequenced. Four new mutations were detected in the hybrid allele and these were subsequently also found in intron 6 of A(2) alleles in other Black African samples. Conclusions: A novel O-1v-A(2) hybrid was defined by ABO exon/intron analysis in five unrelated individuals of African descent with the A(weak)B blood group phenotype.
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| 20. |
- Hosseini Maaf, Bahram, et al.
(författare)
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An extensive polymerase chain reaction-allele-specific polymorphism strategy for clinical ABO blood group genotyping that avoids potential errors caused by null, subgroup, and hybrid alleles
- 2007
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Ingår i: Transfusion. - : Wiley. - 1537-2995 .- 0041-1132. ; 47:11, s. 2110-2125
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Tidskriftsartikel (refereegranskat)abstract
- Background: ABO genotyping is complicated by the remarkable diversity at the ABO locus. Recombination or gene conversion between common alleles may lead to hybrids resulting in unexpected ABO phenotypes. Furthermore, numerous mutations associated with weak subgroups and nondeletional null alleles should be considered. All known ABO genotyping methods, however, risk incorrect phenotype predictions if any such alleles are present. Study Design and Methods: An extensive set of allele-specific primers was designed to accomplish hybrid-proof multiplex polymerase chain reaction (PCR) amplification of DNA fragments for detection of ABO alleles. Results were compared with serologic findings and ABO genotypes defined by previously published PCR-restriction fragment length polymorphism/PCR-allele-specific polymorphism (ASP) methods or DNA sequencing. Results: Phenotypically well-characterized samples from blood donors with common blood groups and rare-subgroup families were analyzed. In addition to the commonly encountered alleles (A(1), A(1(467C > T)), A(2), B, O-1, O-1v, and O-2), the new method can detect hybrid alleles thanks to long-range amplification across intron 6. Four of 12 PCR-ASP procedures are used to screen for multiple infrequent subgroup and null alleles. This concept allows for a low-resolution typing format in which the presence of, for example, a weak subgroup or cis-AB/B(A) is indicated but not further defined. In an optional high-resolution step, more detailed genotype information is obtained. Conclusion: A new genotyping approach has been developed and evaluated that can correctly identify ABO alleles including nondeletional null alleles, subgroups, and hybrids resulting from recombinational crossing-over events between exons 6 and 7. This approach is clinically applicable and decreases the risk for erroneous ABO phenotype prediction compared to previously published methods.
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| 21. |
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| 22. |
- Hult, Annika, et al.
(författare)
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Blood group genotype analysis for the quality improvement of reagent test red blood cells
- 2005
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Ingår i: Vox Sanguinis. - : Wiley. - 1423-0410 .- 0042-9007. ; 88:4, s. 265-270
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Tidskriftsartikel (refereegranskat)abstract
- Background and Objectives Reagent red blood cells (RBCs) for antibody detection should express certain important antigens as a double dose, that is, the donors must be homozygous for the corresponding alleles. Traditionally, dose is determined by serological typing and known allele frequencies. However, RHD zygosity cannot be predicted serologically owing to the absence of an antithetical antigen, and FY zygosity is confounded by two variant haplotypes, FY*0 and FY*X. Furthermore, lack of reagents hampers our ability to type for some clinically important antigen pairs such as Do(a)/Do(b). Materials and Methods Genomic DNA was isolated from reagent RBC samples. Established, validated methods were used to determine the RHD, FY, and DO genotypes. Results Three of 52 D+ samples gave results that differed from the predicted genotype: two presumed (RR1)-R-1 samples and an (RR2)-R-2 sample were shown to be R(1)r" and R(2)r', respectively. Five of 59 samples that were from presumed homozygotes for either FY*A or FY*B were heterozygous, together with either FY*X (three samples) or FY*0 (two samples). Seventy-five samples tested for DO were DO*A/A (n = 14), DO*A/B (n = 39), or DO*B/B (n = 22). Conclusions The results show that serologically determined RhD and Duffy phenotypes of reagent RBCs are unreliable and that antigens we thought were represented as a double dose were single dose. The addition of Dombrock genotyping provides information which is useful in antibody identification. We conclude that selected genotype analyses are a valuable quality assurance measure to ensure that reagent RBCs comply with national and international recommendations for test sensitivity.
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| 23. |
- Hult, Annika K, et al.
(författare)
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A new missense variant in exon 7 of the ABO gene, c.662G>A, in a family with B w phenotype.
- 2022
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Ingår i: Transfusion. - : Wiley. - 1537-2995 .- 0041-1132. ; 62:10, s. 55-58
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Tidskriftsartikel (refereegranskat)abstract
- 1 BACKGROUNDWeak expression of ABO antigens is encountered in the clinical laboratory occasionally, and subgroups of A are more commonly observed in Europeans than subgroups of B. To date, weakly expressing B variant phenotypes have been associated with 38 different alleles according to ISBT (https://www.isbtweb.org/resource/001aboalleles.html). This number is an underrepresentation since there have been several reports of aberrant B expression due to variant alleles since the last update of the ISBT allele table. The current study was initiated by an unusual blood group typing result in a 55-year-old male patient of Czech origin and previously reported as an abstract.12 BRIEF METHODSBlood grouping was performed according to standard blood banking practice, initially using an automatic analyzer (Galileo, Immucor) followed by confirmation with manual gel (BioRad; DG-Gel) and tube agglutination techniques. Initial genotyping analysis was done using a PCR-SSP kit (Innotrain), microarray (BloodChip Reference, Progenika) and subsequently verified by expanded PCR-ASP and PCR-RFLP as described previously.2, 3 ABO exons 1–7 and splice sites were amplified and analyzed, together with the product(s) of PCR-ASP for exons 6–7, by Sanger sequencing.4 A single nucleotide variation (SNV) was detected, and the localization of the affected amino acid is visualized in a 3D-model of ABO glycosyltransferase by Cn3D (v.4.3.1, www.ncbi.nih.gov) and a detailed view obtained by AlphaFold.5, 6 Flow cytometry testing with monoclonal ABO reagents was performed as described previously.73 RESULTSThe proband's red blood cells (RBCs) initially typed as group O but the plasma typing gave negative or weak reactions with test RBCs of group B, depending on the method used, Table 1. An ABO*B.01/O.01.01 genotype was revealed, normally consistent with group B. Screening for selected A and B subgroup allele markers was negative.2 After informed consent, samples from family members were drawn and further investigation was performed.In samples from the proband, his sister and niece, sequence analysis revealed heterozygosity for a SNV in ABO exon 7, c.662G>A (no rs number available) in an otherwise normal ABO*B.01 allele. Significantly weakened B antigen expression was observed in all three individuals. An overview of serological testing and genetic results is shown in Table 1.SNV c.662G>A encodes an amino acid change, p.Gly221Asp. The glycine residue is completely evolutionarily conserved among the members of the GT6 family of glycosyltransferases8 and centrally located in the enzyme, seven amino acids away from the DVD motif (pp. 211–213) that coordinates the Mn2+ ion and the UDP part of the UDP-galactose donor substrate (Figure 1A). However, it is not directly interfering with the catalytic site. Instead, the change of the small neutral glycine to the bulkier and charged aspartic acid is predicted to abolish selected hydrogen bonds and is therefore hypothesized to destabilize the protein conformation (Figure 1B).5, 6
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