RH locus contraction in a novel Dc-/D-- genotype resulting from separate genetic recombination events

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Abstract

BACKGROUND

The rare phenotypes Dc- and D– lack the expression of E/e and CcEe antigens, respectively; their cotransmission in a single family has not been reported.

STUDY DESIGN AND METHODS

Six members of a Chinese family with two exhibiting the Dc- phenotype were studied using standard serologic methods. Rh genotypes were analyzed by Southern blot, and RH loci, by exon PCR. Rh transcripts were characterized by gene-specific RT-PCR and sequencing.

RESULTS

Although Rh typing detected two members as Dc- homozygotes, RFLP analysis and exon PCR showed them to be Dc-heterozygotes with a partial deletion of RHCE. cDNA sequencing showed the expression in the family of normal RHD and RHCe as well as hybrid transcripts, RHD(1–9)/RHCE(10) and RHCE(1–3)/RHD(4–10). Thus, the Dc-members had the genotype of Dc-/D– and expressed both hybrid genes that were inherited from their parents, respectively.

DISCUSSION

This is the first demonstration in a family that the Dc- and D– complexes neither are linked with a normal RHD or RHCE gene. The segregation of these two different hybrid genes with single break points sug-gests their independent genetic origin and provides molecular insights into the dynamic nature of genomic rearrangements leading to RH locus contraction.

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