Multiple isoforms excluding normal RhD mRNA detected in Rh blood group Del phenotype with RHD 1227A allele.

The RhD mRNA was analyzed in both Rh-positive and D(el) phenotypes with RHD 1227A allele through sequencing. As a result, five and six transcripts were detected in Rh-positive and D(el), respectively. Four of them have identical sequences between Rh-positive and D(el). Those are the transcripts with exon 9, exons 8 and 9, exons 7 and 9, and exons 7-9 spliced out compared normal RhD mRNA that was detected in Rh-positive but not in D(el) individuals. Unexpectedly, two additional transcripts were found in D(el) individuals. Its exon 9 or exons 8-9 were spliced out, but interestingly both possess a 170 bp segment of sequence from intron 7 of RHD. We may conclude that a normal RhD protein does not exist in a D(el) individual with RHD 1227A allele since the exon 9 was always spliced out due to the silent mutation at the end of exon 9. The transcripts without exon 9 was also detected in the normal Rh-positive individual and further confirmed by a specific reverse-transcription PCR (RT-PCR) system.