DIAGNOSTIC STRATEGY, GENETIC DIAGNOSIS AND IDENTIFICATION OF NEW MUTATIONS IN INTERMITTENT PORPHYRIA BY DENATURING GRADIENT GEL-ELECTROPHORESIS

Acute intermittent porphyria (ALP) is an autosomal dominant: inherited disease of heme metabolism caused by mutations in the hydroxymethylbi lane synthase gene. Diagnosing AIP during an acute attack using tradit ional biochemical markers is unproblematic, but it can be difficult to obtain a definite diagnosis in asymptomatic carriers, These limitatio ns may, however, be solved through a genetic approach for diagnosing A IP carrier status. A mutation screening assay based on the denaturing gradient gel electrophoresis (DGGE) principle was established in a set up that allows within 24 hr to pinpoint which of the 15 exons of the h ydroxymethylbilane synthase gene carries the underlying mutation, and thereby reduces subsequent sequencing, needed to determine the specifi c mutation, to this particular gene region. To evaluate sensitivity an d specificity of the DGGE assay, samples from 22 AIP patients with kno wn mutations and six healthy controls were examined in a blinded desig n. Following unblinding, it was revealed that in all 22 AIP samples th e correct mutation carrying region had been pointed out. In two sample s containing a previously undescribed polymorphism, this additional re gion was also pointed out. All controls were correctly characterized a s normal in the DGGE: assay. Subsequently, to evaluate the assay in th e clinical setting, samples from six previously uncharacterized Danish AIP probands were examined and the underlying mutation detected in al l six, In conclusion, a simple and sensitive mutation screening assay based on the DGGE principle allows genetic diagnosis of AIP in a routi ne setting and may be used as an additional tool in genetic counseling of AIP families. (C) 1997 Wiley-Liss, Inc.