Cloning of rat gene encoding the histo-blood group B enzyme: rat more that one Abo gene

D ow nloaded from 2Abstract A genomic DNA fragment corresponding to exon 7 of the human ABO gene was amplified from rats of several inbred and outbred strains. Five different sequences were obtained, four of them corresponding to A-type sequences and one to a B-type sequence based on the amino-acids equivalent to residues at positions 266 and 268 of the human enzymes. In rats from inbred strains, a single A-type sequence and the unique B-type sequence were found, whereas some animals of outbred strains presented two or three A-type sequences along with the B-type sequence. The complete coding sequence of the B-type gene was obtained and identification of the exon-intron boundaries, determined by comparison with rat genomic sequences from data banks, revealed that the rat B-type gene structure is identical with that of the mouse Abo gene. Compared with the human ABO gene and the rat A gene, it lacks exon 4. Like the rat A gene (symbol: Abo), the rat B gene (symbol: Abo2) is located on chromosome 3q11-q12. It could b