Physical and genetic mapping of the serpin gene cluster at 14q32.1: allelic association and a unique haplotype associated with alpha 1-antitrypsin deficiency

The alpha 1-antitrypsin (PI) gene is part of a cluster of structurally related serine protease inhibitor genes localized at chromosome 14q32.1, a cluster that includes the alpha 1-antichymotrypsin (AACT), protein C inhibitor (PCI), and corticosteroid-binding globulin (CBG) genes and the alpha 1-antitrypsin-like pseudogene (PIL). The order of the genes is refined here by genetic mapping using simple tandem repeat polymorphisms (STRPs) and by physical mapping in YACs. The order of the genes is (centromere)-CBG-PIL-PI-PCI-AACT-(telomere). Analysis of DNA haplotypes comprising STRP and RFLP markers in the serpin genes reveals considerable allelic association throughout the cluster. Furthermore, the common alpha 1-antitrypsin deficiency allele, PI*Z, has a unique DNA haplotype at the CBG, PIL, and PI loci, which extends over 60 kb in 97% of cases and in 44% of cases includes the PCI and AACT loci. This unique haplotype will be of use in examining a number of other diseases, particularly those with an inflammatory component, thought to be associated with alpha 1-antitrypsin deficiency or partial deficiency.