K. Isa

Anaphylactic transfusion reactions in haptoglobin-deficient patients with IgE and IgG haptoglobin antibodies

BACKGROUND : Patients with haptoglobin deficiency associated with haptoglobin IgG antibodies, who experienced severe nonhemolytic transfusion reactions (NHTRs), have been identified in Japan. Haptoglobin deficiency therefore might be a risk factor for NHTRs.

Expression of ABO blood-group genes is dependent upon an erythroid cell-specific regulatory element that is deleted in persons with the B(m) phenotype.

The ABO blood group is of great importance in blood transfusion and organ transplantation. However, the mechanisms regulating human ABO gene expression remain obscure. On the basis of DNase I-hypersensitive sites in and upstream of ABO in K562 cells, in the present study, we prepared reporter plasmid constructs including these sites. Subsequent luciferase assays indicated a novel positive regulatory element in intron 1. This element was shown to enhance ABO promoter activity in an erythroid cell-specific manner. Electrophoretic mobility-shift assays demonstrated that it bound to the tissue-restricted transcription factor GATA-1. Mutation of the GATA motifs to abrogate binding of this factor reduced the regulatory activity of the element. Therefore, GATA-1 appears to be involved in the cell-specific activity of the element. Furthermore, we found that a partial deletion in intron 1 involving the element was associated with B(m) phenotypes. Therefore, it is plausible that deletion of the erythroid cell-specific regulatory element could down-regulate transcription in the B(m) allele, leading to reduction of B-antigen expression in cells of erythroid lineage, but not in mucus-secreting cells. These results support the contention that the enhancer-like element in intron 1 of ABO has a significant function in erythroid cells.

Mutation of the GATA site in the erythroid cell–specific regulatory element of the ABO gene in a Bm subgroup individual

The ABO blood group is important in blood transfusion. Recently, an erythroid cell–specific regulatory element has been identified in the first intron of ABO using luciferase reporter assays with K562 cells. The erythroid cell–specific regulatory activity of the element was dependent upon GATA‐1 binding. In addition, partial deletion of Intron 1 including the element was observed in genomic DNAs obtained from 111 Bm and ABm individuals, except for one, whereas the deletion was never found among 1005 individuals with the common phenotypes.

Deletion of the RUNX1 binding site in the erythroid cell-specific regulatory element of the ABO gene in two individuals with the Am phenotype.

An erythroid cell‐specific regulatory element, referred to as the +5·8‐kb site, had been identified in the first intron of the human ABO blood group gene. Subsequent studies revealed that either a 5·8‐kb deletion including the +5·8‐kb site or disruption of a GATA factor binding motif at the site was present in all Bm and ABm individuals examined. We investigated the molecular mechanism of the Am phenotype, which is analogous to the Bm phenotype.

Molecular basis for D− Japanese: identification of novel DEL and D− alleles

The occurrence of D− is approximately 0·5% in Japanese, but DEL in apparently D− individuals is relatively common compared with that in Caucasian populations. On the basis of molecular genetics, we examined D− Japanese blood donors.

JK null alleles identified from Japanese individuals with Jk(a−b−) phenotype

The Kidd blood group system consists of three common phenotypes: Jk(a+b−), Jk(a−b+) and Jk(a+b+), and one rare phenotype, Jk(a−b−). Jka/Jkb polymorphism is associated with c.838G>A (p.Asp280Asn) in exon 9 of the JK (SLC14A1) gene, and the corresponding alleles are named JK*01 and JK*02. The rare phenotype Jk(a−b−) was first found in a Filipina of Spanish and Chinese ancestry, and to date, several JK null alleles responsible for the Jk(a−b−) phenotype have been reported. We report seven novel JK null alleles, 4 with a JK*01 background and 3 with a JK*02 background, identified from Jk(a−b−) Japanese.

Presence of nucleotide substitutions in transcriptional regulatory elements such as the erythroid cell-specific enhancer-like element and the ABO promoter in individuals with phenotypes A3 and B3, respectively

An erythroid cell‐specific regulatory element, referred to as the +5.8‐kb site, has been identified in the first intron of the human ABO blood group gene. Subsequent studies have revealed involvement of deletion or mutation at the site in phenotypes Am, Bm and ABm. We investigated the molecular mechanisms involved in the A3 and B3 phenotypes.

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 (Bm5·8) 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 (Bm3·0) was demonstrated in the remaining individual. Comparisons of single‐nucleotide polymorphisms and microsatellites in intron 1 between Bm5·8 and Bm3·0 suggested that these deletions occurred independently.

Weak D alleles in Japanese: a c.960G>A silent mutation in exon 7 of the RHD gene that affects D expression

The molecular basis of the weak D phenotype has been investigated for many years, and more than 80 different alleles producing weak D phenotypes have been identified. Most alleles producing weak D phenotypes have a single missense mutation in exons corresponding to a transmembrane domain of the RhD polypeptide. We report here RHD alleles with single nucleotide mutations in Japanese accounting for weak expression of D antigen.

Prevalence of RHD alleles in Japanese individuals with weak D phenotype: Identification of 20 new RHD alleles

We identified 46 different RHD alleles from 226 Japanese individuals with weak D phenotype, 26 of which had been previously described and 20 that were novel. Among these weak D individuals, the alleles with c.960G>A, c.845G>A (RHD*15) or c.1013T>C (RHD*01W.24) mutations were most prevalent with relative occurrences of 36·7%, 15·9% and 9·7%, respectively. These findings demonstrate that the prevalence of common weak D alleles in the Japanese population significantly differs from that of Caucasian populations.