Insights into RHCE Molecular Analysis in Samples with Partial D Variants: the Experience of Western France

Abstract

Background: Although systematic blood group genotyping of patients/donors is virtually possible, serological studies remain the gold standard to identify samples of clinical interest that may be further genotyped. In this context, we sought to identify variant D alleles that are likely to be clinically relevant in terms of other Rh antigens in a subset of population genotyped in Western France.

Methods: Samples presenting with the RHD*weak D type 4.2.2 allele (n = 47) were selected for the study. RHCE exons 1-7 were directly sequenced, and expression of Rh antigens was predicted on the basis of the molecular data.

Results: Of the 47 samples tested, 19 (40.4%) were predicted to be of potential clinical interest. Moreover, we could show that selecting the samples to be genotyped by the nature of their variant D allele (i.e., RHD*weak D type 4.2.2 allele) rather than by their Duffy-null status appears to increase significantly the likelihood of identifying clinically relevant individuals for Rh status.

Conclusion: On the basis of our findings we suggest that all individuals genotyped as weak D type 4.2.2 should be systematically screened for RHCE variants by molecular analysis on a routine basis.

Keywords: Antigens; Blood group; Genotyping; RHCE; RHD; Variant alleles.

Fig. 1

RHCE alleles and associated phenotype found in RHD*weak D type 4.2.2 samples. The left panel illustrates the RHCE gene, including the 10 exons (each represented by a white square; left-to-right: exons 1 to 10) and the respective position of variants in each allele (black, vertical bar); note that exons 8 to 10 have not been sequenced. N/A: not applicable; *Phenotype different from the reference RHCE*ce allele.

Fig. 2

Typical RHCE-QMPSF profiles obtained in samples with genotypes A RHCE*ce.04/RHCE *ce.04, B RHCE*ce.04/ RHCE*ce(c.712A, c.733G, c.787G, c.800A, c.916G), C RHCE *ce/RHCE*ce.04, D RHCE*ce/RHCE*ce.05, E RHCE*ce.20.01/RHCE *ce.20.02, and F RHCE*Ce/RHCE*ce (calibrator). Respective peak IDs are indicated below the figure; e1C to e10: RHCE exons 1 to 10. *Exon numbering different from what expected for a homozygous RHCE*ce sample [22].