HETERODUPLEX ANALYSIS DETECTS FRAMESHIFT AND POINT MUTATIONS IN PATIENTS WITH ACUTE INTERMITTENT PORPHYRIA

We used heteroduplex analysis to screen for mutations in the porphobil inogen deaminase gene in 21 patients. with acute intermittent porphyri a (AIP). Unique banding patterns were investigated by direct sequencin g of polymerase chain reaction products and, when indicated, sequencin g of cloned DNA containing the exon of interest. Two frameshift mutati ons were found, a 2-bp deletion in exon 5 and a 1-bp insertion in exon 7. Both mutations generate a premature stop codon. Two point mutation s, in exons 10 and 14, were also observed. The C-->T mutation in exon 10 codes for an Arg(173) to Trp substitution, while a G-->A mutation i n exon 14 changes Trp(283) into a premature stop codon. This study ext ends the spectrum of mutations that cause AIP and demonstrates the uti lity of heteroduplex analysis as a screening technique.