title: Hydroxymethylbilane synthase gene mutations and polymorphisms in Brazilian families with acute intermittent porphyria.
abstract: Acute intermittent porphyria (AIP), an autosomal dominant disorder, is caused by a deficiency of hydroxymethylbilane synthase (HMBS). In the present study, we sought to establish a correlation between HMBS activity with the presence of mutations and polymorphisms. Enzyme activity was measured in red blood cells of four Brazilian unrelated AIP families (n = 124) and in blood donors (n = 80). The HMBS mutations in AIP family members were studied by PCR-SSCP followed by direct sequencing. Six intragenic SNPs (1345 G>A, 1500 T>C, 2377 C>A, 2478 A>G, 3581 A>G, and 7064 C>A) were determined by PCR-RFLP. Abnormal SSCP patterns in exons 7, 9, 12, and 15 were observed. DNA sequencing analysis revealed one nonsense mutation, R149X, two missense mutations, G111R and L338P, and one deletion, CT 730-731. All mutation carriers had lower enzyme activity. All polymorphisms, except 2377 C>A and 7064 C>A, showed no significant differences compared with previous reports. Mutation screening allowed the detection of the missense mutation, L338P, and the 730_731delCT deletion, two as yet unreported mutations in Brazilian AIP patients. Our findings also showed a high frequency of 2478 A>G and 3581 A>G polymorphism combinations suggesting that these polymorphisms contributed to enzymatic activity reduction in our study population.
authors.affiliation: Departamento de Patologia, Faculdade de Medicina, Universidade Federal Fluminense, Niterói, RJ, Brazil.
authors.forename: Ana Denise Gomes
authors.initials: AD
authors.lastname: Gonzaga
authors.forename: Lidia Maria da Fonte
authors.initials: LM
authors.lastname: de Amorim
authors.forename: Ana Beatriz Monteiro
authors.initials: AB
authors.lastname: Fonseca
authors.forename: Tatiana Lucia Santos
authors.initials: TL
authors.lastname: Nogueira
authors.forename: Olga Maria Diniz
authors.initials: OM
authors.lastname: Pereira
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Nagai
authors.forename: Orlando Cesar
authors.initials: OC
authors.lastname: de Oliveira Barretto
authors.forename: Georgina Severo
authors.initials: GS
authors.lastname: Ribeiro
mesh_terms: D001938:Brazil; D004252:DNA Mutational Analysis; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D011163:Hydroxymethylbilane Synthase / Q000235:genetics*; D008297:Male; D009154:Mutation; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D018807:Polymorphism, Single-Stranded Conformational; D017118:Porphyria, Acute Intermittent / Q000235:genetics*
chemical_list: D011163:Hydroxymethylbilane Synthase
keywords: Acute intermittent porphyria (AIP); DNA sequencing; enzyme activity; hydroxymethylbilane synthase (HMBS); polymerase chain reaction (PCR); restriction fragment length polymorphism (RFLP); single nucleotide polymorphism (SNP); single-stranded conformational polymorphism (SSCP)