Identification of a novel frequent RHCE*ce308T variant allele in Chinese D- individuals, resulting in a C+c- phenotype.

Background: The RHCE allele is highly polymorphic; more than 60 variants have been described leading to diminished expression of C, c, E, and e antigens. Not much is known about the prevalence of RHCE variants in the Chinese population. Individuals carrying a variant are at risk to develop alloantibodies in response to mismatched pregnancy or transfusion. In this study, phenotyping and genotyping of the RHCE allele in Chinese donors revealed a new clinically relevant mutation.

Study Design And Methods: Blood samples from 200 D- and 200 D+ Chinese donors were analyzed by the RH multiplex ligation-dependent probe amplification (MLPA) assay and compared to serologically typed RhCE phenotypes, when available. All exons of the RHCE gene were sequenced in samples with aberrant genotyping results. The phenotype of the new variant RHCE allele was tested by transducing cultured human erythroblasts.

Results: Aberrant copy numbers for Exon 2 of the RHCE gene were discovered by MLPA in six D- donors (6/200), but not in D+ donors (0/200). Sequencing of the RHCE gene in these six donors identified a new variant RHCE*ce308C>T (p.103Pro>Leu) allele with an allele frequency of 0.015 within the D- individuals in this study. This variant was not detected in D+ individuals showing linkage with the D- haplotype. Serologically weak C expression and loss of c expression was demonstrated on donor red blood cells. In vitro transfection studies of the RHCE*ce308T variant in cDe/ce and CDe/CDe erythroblasts confirmed that the variant is associated with anti-C reactivity while abolishing c expression.

Conclusion: Genotyping of individuals carrying this variant by standard RHCE genotyping might falsely predict a C- phenotype or a c+ phenotype. This new variant should be taken into account in RHCE genotyping assays designed for the Chinese population.