Résumé
We have cloned and mapped a 90-kb region spanning the human genomic amiloride-sensitive
Na
+
H
+
antiporter gene on overlapping cosmid clones. This cloned region extends 27 kb upstream of the 5′ end of the longest antiporter cDNA and reveals a primary transcription unit of at least 60 kb. Using these genomic clones we have identified polymorphisms in the antiporter gene in human genomic DNA cleaved with enzymes
TaqI and
MspI; both are two-allele systems. We have localized both polymorphisms to the same segment within an intron of the antiporter transcription unit. Observed heterozygosity for both markers is 47% in 175 unrelated individuals, with the two polymorphic systems showing complete linkage disequilibrium. We have determined genotypes at the antiporter locus in 667 individuals in 59 reference families. Linkage analysis using 28 other markers on human chromosome 1 precisely locates the antiporter gene (locus APNH) on the genetic map of 1p. The antiporter gene is closely flanked by two highly informative loci, lying 3 cM proximal to the rhesus blood group locus (Rh) and 4 cM distal to the anonymous DNA marker CMM8 (locus D1S79). These antiporter polymorphisms and informative flanking markers will prove useful in genetic linkage studies employing the antiporter gene.