RHCE nucleotide 48 polymorphism in Argentinean donors carrying RHD*weak D type 1 alleles on R0 haplotypes

PRINCIPI C; TRUCCO BOGGIONE C; MUFARREGE N; LUJÁN BRAJOVICH M; MATTALONI S; ENSINCK A; BIONDI C; COTORRUELO C

Milán

Congreso; 31st Regional Congress of the International Society of Blood Transfusion; 2021

International Society of Blood Transfusion

Background: RHD*weak D type 1 variant is strongly associated with RHCE*Ce allele on R1 haplotypes. However, previous research conducted in our laboratory showed that in approximately 17% of Argentineans with weak D type 1 phenotype, the RHD*weak D type 1 allele is found on R0 haplotypes. RHCE*Ce and RHCE*CE alleles carry a cytosine at nucleotide 48 (c.48C) in RHCE exon 1 while RHCE*ce and RHCE*cE are generally associated to a guanine at position 48 (c.48G). It has been observed that c.48C single nucleotide variation (SNV) is also found in some RHCE*ce variants (RHCE*ce.01) in the context of R0 haplotypes.Aims: The aim of this study was to analyse the RHCE polymorphism at nucleotide 48 in Argentinean donors carrying RHD*weak D type 1 alleles on R0 haplotypes.Methods: DNA samples from 20 Dweak type 1ccee and 41 Dccee Argentinean donors were investigated. Two PCR procedures each containing forward primers targeting c.48C or c.48G SNVs in RHCE exon 1, respectively, paired with an RHCE intron 1-specific reverse primer were used to investigate RHCE nucleotide 48 polymorphism. RHD zygosity was investigated by PCR-RFLP. The presence of a hybrid Rhesus box, that implies a RHD hemizygous status, was demonstrated by amplification of the downstream and hybrid Rhesus boxes followed by digestion of the PCR products with endonuclease PstI.Results: Molecular analysis allowed the detection of c.48C and c.48G polymorphisms in all samples carrying RHD*weak D type 1 alleles on R0 haplotypes (n=20, 100%). On the other hand, 19 of the 41 (46.3%) Dccee samples harboured c.48C and c.48G SNVs while 22 (53.7%) only showed guanine at position 48. All weak D type 1 samples on R0 haplotypes were RHD hemizygous and only 1 RHD homozygous sample was found in the group of Dccee samples, which has both c.48C and c.48G SNVs.Conclusions: These results suggest that RHD*weak D type 1 alleles is linked to RHCE*ce.01 variant when found on R0 haplotypes. The c.48G>C transversion in RHCE exon 1 leads to p.Trp16Cys, usually present in conventional RHCE*Ce and RHCE*CE alleles, while Trp16 is associated with RHCE*ce and RHCE*cE alleles. The presence of Cys16 in RHCE*ce is associated with the R0 haplotype in Africans, leading to a weak e antigen expression on red blood cells. The finding of 46.3% of Dccee samples carrying RHCE*ce.01 alleles can be attributed to African ancestry in the Argentinean population. Genetic recombination events occurring in such admixed population could account for the strong association between a Caucasian allele (RHD*weak D type 1) and an African allele (RHCE*ce.01) found on R0 haplotypes.