cDNA sequence and chromosome localization of pig alpha 1,3 galactosyltransferase

Human serum contains natural antibodies (NAb), which can bind to endothelial cell surface antigens of other mammals. This is believed to be the major initiating event in the process of hyperacute rejection of pig to primate xenografts. Recent work has implicated galactosyl alpha 1,3 galactosyl beta 1,4 N-acetyl-glucosaminyl carbohydrate epitopes, on the surface of pig endothelial cells, as a major target of human natural antibodies. This epitope is made by a specific galactosyltransferase (alpha 1,3 GT) present in pigs but not in higher primates. We have now cloned and sequenced a full-length pig alpha 1,3 GT cDNA. The predicted 371 amino acid protein sequence shares 85% and 76% identity with previously characterized cattle and mouse alpha 1,3 GT protein sequences, respectively. By using fluorescence and isotopic in situ hybridization, the GGTA1 gene was mapped to the region q2.10-q2.11 of pig chromosome 1, providing further evidence of homology between the subterminal region of pig chromosome 1q and human chromosome 9q, which harbors the locus encoding the AB0 blood group system as well as a human pseudogene homologous to the pig GGTA1 gene.