A partial deletion of intron 1 involving the regulatory element is found in genomic DNAs derived from persons with Bm. (A) Schematic representation of the genomic organization of the human ABO gene, locations of the erythroid cell–specific regulatory element, PCR-amplified fragments, and a partial deletion of intron 1 in the Bm allele. The top diagram indicates ABO exons 1-7 as solid boxes. It is noteworthy that the direction of ABO is opposite of that in Figure 1. The clear box indicates the location of the erythroid cell–specific regulatory element. Positions are indicated relative to the ATG translation start site in exon 1. PCR-amplified fragments in PCR1-PCR9 are indicated by broken lines, and the primers used are represented as thick lines at both ends of individual broken lines. The relationship between the PCR amplifications and primers used is shown in Table 3. Deleted nucleotides in intron 1 of the Bm allele are indicated by a V-shaped segment. (B) A partial deletion of intron 1 was found in genomic DNA derived from a person with Bm. PCR1-PCR4 were carried out with genomic DNAs derived from persons with B and Bm using various sets of primers, followed by electrophoresis through 0.5% agarose gel and staining with ethidium bromide. Gene Ladder Wide 2 (Nippon Gene) was used as a molecular size marker. (C) Partial deletion found in genomic DNAs obtained from 10 persons with Bm or ABm. PCR4 amplifications were carried out using genomic DNAs derived from persons with A, B, O, AB, Bm, and ABm, followed by electrophoresis through 0.5% agarose gel and staining with ethidium bromide. Representative PCR products from 10 persons with Bm or ABm are displayed. The shorter PCR4 products obtained from those persons were sequenced, confirming that the deletion was located between +5137 and +10914.
