Molecular cloning of a human genomic region containing the H blood group alpha(1,2)fucosyltransferase gene and two H locus-related DNA restriction fragments. Isolation of a candidate for the human Secretor blood group locus.

We have used the human H blood group alpha(1,2)fucosyltransferase (FUT1) cDNA to screen chromosome 19 cosmid libraries in a search for the human Secretor (Se) blood group gene (FUT2). One cosmid has been isolated that contains two distinct segments that cross-hybridize with FUT1. We have assembled a 100-kilobase (kb) cosmid contig, localized to 19q13.3, encompassing FUT1 and the two FUT1-related sequences, termed Sec1 and Sec2, for Secretor candidate 1 and 2. Sec1 and Sec2 are separated by 12 kb and are 65.5 kb and 35 kb apart, respectively, from the FUT1 gene. We used a cosmid-dependent direct cDNA selection method to clone a cDNA corresponding to a transcript that emanates from Sec2. This cDNA detects a 3.35-kb transcript in human tissues known to express the Se locus. Together with sequence and expression data reported in the accompanying article (Kelly, R. J., Rouquier, S., Giorgi, D., Lennon, G. G., and Lowe, J. B. (1995) J. Biol. Chem. 270, 4640-4649), these data demonstrate that Sec2 corresponds to the human Se blood group locus (FUT2). Our results furthermore define the physical relationship between the H and Se loci and confirm a hypothesis that these two loci represent distinct but closely linked alpha(1,2)fucosyltransferase genes.