MN typing discrepancies based on GYPA-B-A hybrid.

BACKGROUND AND OBJECTIVES: Gene conversion events between GYPA and GYPB or GYPA and GYPE are facilitated by the close chromosomal proximity and high degree of sequence homology and can lead to the formation of GP hybrid genes. Discrepant results between blood group genotyping and haemagglutination in 22 random blood donors induced molecular characterization. MATERIALS AND METHODS: Sequence analysis of GYPA exons 1-7 and GYPB exons 1-5 was performed for gDNA and cDNA. The linkage of the nucleotide alterations was defined by haplotype separation. RESULTS: DNA analysis demonstrated a normal GYPA haplotype (GYPA*N n = 20, GYPA*M n = 2) with an altered GP hybrid nucleotide sequence in trans. A GYPB homologue sequence of minimal 10-bp encompassing intron 1 and exon 2 was translated into GYPA, accounting for an amino acid substitution from arginine to glutamic acid at position 13 (38 C>A). Genomic DNA analysis demonstrated the cis-linkage of the hybrid nucleotide sequence with each GYPA(Ser20, Gly24) (n = 20) associated with the expression of M and GYPA(Leu20, Glu24) (n = 2) encoding the N phenotype. The serologic data indicate that the changes do not affect the expression of a normal M and N antigen. cDNA sequences confirmed the gDNA results and furthermore identified a heterozygous deletion of GYPB exon 2 in all probands. CONCLUSION: The results document a GYPA-B-A hybrid gene, probably produced via a single unequal homologous recombination event. A segmental transfer of GYPB seems most likely accounting for the allelic dropout.

On the trail of anti-CDE to unexpected highlights of the RHD*weak 4.3 allele in the Upper Austrian population.

BACKGROUND AND OBJECTIVES: The application of a commercial available microcolumn system for ABO/RH determination lead to irregular results in CDE typing of seemingly D- blood samples. In this study, we introduce a comprehensive serological and molecular work-up of a novel haplotype carrying the RHD*weak 4.3 in combination with an aberrant RHCE*ce. MATERIALS AND METHODS: The molecular background was characterized by RHD and RHCE-specific DNA sequencing, RHD cDNA sequencing and RHD zygosity testing. Haplotype-specific extraction and inheritance analysis were initiated to determine the linkage of the polymorphisms. The genetic admixture was studied by whole genome SNP array analysis. Serology was done using commercial available standard techniques and by in-house sera likewise. RESULTS: All samples (n = 29) were shown to harbour an altered RHD(T201R, F223V, P291R) allele known as RHD*weak 4.3 associated with a RHCE*ce(W16C, A36T, L245V) gene formation, expressing C(X) and VS. Both anti-C(X) and anti-V/VS were detected as contaminating antibodies in a commercial available microcolumn system for ABO/RH determination accounting for the positive results in CDE typing. Compared with other population data, the samples were clearly identified as Caucasian. CONCLUSION: The RHD*weak 4.3 allele with markedly reduced antigen D expression was shown to be associated with an altered RHCE gene formation leading to the expression of C(X) and VS. Its frequency was estimated 1 in 854 among apparently D- Upper Austrian blood donors.