Detection of alpha 1-antitrypsin Z and S mutations by polymerase chain reaction-mediated site-directed mutagenesis.

alpha 1-Antitrypsin (A1AT) deficiency is a relatively common autosomal recessive disease, resulting most often from a single base pair (1 bp) substitution called the Z mutation. Previous genetic tests for carriers and affected patients have relied on quantitative binding of radioactive probes to an amplified gene product, because the mutation does not occur within a restriction enzyme site. Using polymerase chain reaction (PCR)-mediated site-directed mutagenesis, one can introduce a base substitution near the mutation site, such that an inexpensive restriction enzyme (Taq I) can be used to differentiate normal subjects, carriers, and affected patients. We have applied this method to the detection of the Z mutation and the S mutation, which in heterozygotes with a Z allele may lead to the development of symptoms similar to those in ZZ homozygous subjects.