J. A. Condon

A novel cis‐AB variant allele arising from a nucleotide substitution A796C in the B transferase gene

A novel cis-AB variant allele arising from a nucleotide substitution A796C in the B transferase gene Cis-AB is a rare phenotype of the ABO blood group system.1 Serologically, it is characterized by the presence of A, weakened B, and elevated H antigens on the RBCs. A nonautoanti-B is usually detected in the serum. Of the studies that have reported the nucleotide (nt) sequence of the cisAB allele, all have demonstrated an A allele bearing the G803C nt substitution characteristic of the B allele.2-4 This nt substitution results in the amino acid (aa) substitution, Gly268→Ala, at one of two critical positions for determining A/B-transferase specificity, with the other position being aa 266 encoded by nt 796.5 Here we report the identification of a novel cis-AB allele* that appears to have arisen from a single nt substitution at position 796 in the B-transferase gene. The propositus, a 37-year-old Vietnamese man, presented during routine blood grouping and screening for related-donor organ matching. By serologic typing, the propositus typed as A2Bweak with elevated H antigen on his RBCs, while a non-autoanti-B and a weak anti-A1 were detected in his serum. The father of the propositus also demonstrated this phenotype. Transfersase studies could not be conducted. The three siblings of the propositus all typed as group O. Thus, it was deduced that the A2Bweak phenotype of the father arose from a cis-AB allele that had been passed on to the propositus. To identify the genetic basis of this observation, molecular analysis was performed on all direct family members using PCR-sequence-specific oligonucleotide (SSO),6 PCR-restriction fragment length polymorphism (RFLP),7 and sequence analysis (the latter performed by two independent laboratories: Sequence Facility, Department of Microbiology, Monash University, Clayton, VIC, Australia; and Flinders University Automated DNA Sequencing Facility, Flinders Medical Centre, Bedford Park, SA, Australia). The ABO genotype of the mother of the propositus was found to be BO1v, and all the siblings of the propositus were O1vO1v. By PCR-RFLP, the propositus demonstrated B-allele specificity at nt positions 526 and 703, but not at 796, and O1v-allele specificity at nt positions 646 and 771. Sequence analysis of the region spanning nt 411-892 of exon 7 of both the propositus and the father confirmed the B-allele specificity at nt positions 526, 657, 703, and 803, but it also revealed a cytosine residue at nt 796, which is indicative of an A allele (Fig. 1). A final genotype of cis-ABvar/O1v was assigned to both persons: the nomenclature cis-ABvar is proposed to distinguish this variation from the gene configuration previously identified.2-4 Figure 2 shows the pedigree of the family. The data suggest that the cis-AB allele described in this study arose from a point mutation at nt 796 of a seemingly normal B allele. In this case, the mutation involved the substitution of the B-transferase-specific adenosine residue with an A-transferase-specific cytosine residue. An A796C substitution results in the aa substitution Met266→Leu, which changes the sugar donor specificity at that site to an A-transferase and could give rise to a bifunctional transferase, as is suggested by the serologic findings presented in this study. Other molecular mechanisms, such as recombination between A and B alleles, may also provide an ex* Footnote: The nucleotide sequence of this allele has been listed on GenBank, Accession Number AF062487. Fig. 1. The nt sequence analysis at and around nt 796 of exon 7 of the cis-ABvar allele. Cytosine (C) residue at nt 796 indicated by arrow. “N” at nt 803 signifies the presence of two nts, cytosine and guanosine, which are indicative of a B allele and an O1v allele, respectively.

The RHD(1227G>A) DEL‐associated allele is the most prevalent DEL allele in Australian D– blood donors with C+ and/or E+ phenotypes

Red blood cells (RBCs) with D antigen levels only detected by anti‐D adsorption‐elution and an antiglobulin test express a DEL phenotype. For two DEL types, including RHD(1227G>A), immunization of D– recipients has been reported. This studys aim was to measure the prevalence of DEL‐associated RHD alleles in a cohort of Australian D– donors to develop a model to estimate alloimmunization risk.

Diverse and novel RHD variants in Australian blood donors with a weak D phenotype: implication for transfusion management

Variant RHD genes associated with the weak D phenotype can result in complete or partial D‐epitope expression on the red cell. This study examines the genetic classification in Australian blood donors with a weak D phenotype and correlates RHD variants associated with the weak D phenotype against D‐epitope profile.

Duffy blood group phenotype–genotype correlations using high‐resolution melting analysis PCR and microarray reveal complex cases including a new null FY*A allele: the role for sequencing in genotyping algorithms

Duffy blood group phenotypes can be predicted by genotyping for single nucleotide polymorphisms (SNPs) responsible for the Fya/Fyb polymorphism, for weak Fyb antigen, and for the red cell null Fy(a−b−) phenotype. This study correlates Duffy phenotype predictions with serotyping to assess the most reliable procedure for typing.

A novel FY*A allele with the 265T and 298A SNPs formerly associated exclusively with the FY*B allele and weak Fyb antigen expression: implication for genotyping interpretative algorithms

An Australian Caucasian blood donor consistently presented a serology profile for the Duffy blood group as Fy(a+b+) with Fya antigen expression weaker than other examples of Fy(a+b+) red cells. Molecular typing studies were performed to investigate the reason for the observed serology profile.

Massively parallel sequencing in complex blood group investigations: Resolving the previously unresolvable.

Conventional cytogenetic karyotyping and targeted FISH analysis have been the established standard of care in investigating chronic lymphocytic leukaemia. These methods whilst providing prognostic and response prediction are subject to a number of limitations including low level of resolution, failure to achieve the representative cell line in culture and the restrictions of targeted investigation by FISH. Whole genome microarray technology has now superseded conventional cytogenetics in the diagnosis of constitutional anomalies due its higher resolution. The technology has the added benefit of detecting copy neutral loss of heterozygosity (CNLOH) and complex rearrangements such as chromothripsis. We performed an unbiased comparison of findings from SNP microarray using the CytoScan750K SNP Array (Affymetrix), conventional karyotype analysis and FISH on 50 CLL patients. The results illustrate a higher detection rate for pathogenic abnormalities in molecular karyotyping compared to conventional 40/50 (80%) and 22/50 (44%), respectively. The detection of additional pathogenic abnormalities not seen by microscopy accounted for 23/50 (46%) and CNLOH detected for chromosome 13, 20 and 22 in 7/50 (14%). We demonstrate the benefits of SNP based whole genome profiling of CLL and propose its inclusion in the testing regime for the diagnosis and management of CLL patients.