Molecular defects of the RHCE gene in Rh-deficient individuals of the amorph type

The deficiency of Rh proteins on the red blood cells from individuals of the Rhnull amorph type may be the result of homozygosity for a silent allele at the RH locus. This phenotype is also associated with the lack or reduced expression of glycoproteins (Rh50, CD47, LW, and glycophorin B), which interact with Rh polypeptides to form the multisubunit Rh membrane complex. In this study, we describe two molecular alterations affecting the RHCE gene in two unrelated Rhnull amorph individuals bearing Rh50 and CD47 normal transcripts. The first type of mutation, located at the donor splice-site in intron 4, induced the activation of two cryptic splice-sites within this intron and one such site in exon 4 that all generated aberrant transcripts. The second type of mutation affected the coding region and introduced a frameshift and a premature stop codon resulting in a shorter predicted protein (398 v 417 residues), including a completely different C-terminus of 76 amino acids. This suggests that protein folding and/or protein-protein interaction mediated by the C-terminal domain of the Rh proteins may play a role in the routing and/or stability of the Rh membrane complex.