title: Phenylalanine hydroxylase deficiency: molecular epidemiology and predictable BH4-responsiveness in South Portugal PKU patients.
abstract: Hyperphenylalaninemia (HPA, OMIM #261600), which includes phenylketonuria (PKU), is caused by mutations in the gene encoding phenylalanine hydroxylase (PAH), being already described more than 600 different mutations. Genotype-phenotype correlation is a useful tool to predict the metabolic phenotype, to establish the better tailored diet and, more recently, to assess the potential responsiveness to BH(4) therapy, a current theme on PKU field. The aim of this study was the molecular analysis of the PAH gene, evaluation of genotype-phenotype relationships and prediction of BH(4)-responsiveness in the HPA population living in South Portugal. We performed the molecular characterization of 83 HPA patients using genomic DNA extracted from peripheral blood samples or Guthrie cards. PAH mutations were scanned by PCR amplification of exons and related intronic boundaries, followed by direct sequence analysis. Intragenic polymorphisms were determined by PCR-RFLP analysis. The results allowed the full characterization of 67 patients. The mutational spectrum encompasses 34 distinct mutations, being the most frequent IVS10nt-11G>A (14.6%), V388M (10.8%), R261Q (8.2%) and R270K (7.6%), which account for 46% of all mutant alleles. Moreover, 12 different haplotypes were identified and most mutations were associated with a single one. Notably, more than half of the 34 mutations belong to the group of more than 70 mutations already identified in BH(4)-responsive patients, according to BIOPKU database. Fifty one different genotypic combinations were found, most of them in single patients and involving a BH(4)-responsive mutation. In conclusion, a significant number (30-35%) of South Portugal PKU patients may potentially benefit from BH(4) therapy which, combined with a less strict diet, or eventually in special cases as monotherapy, may contribute to reduce nutritional deficiencies and minimize neurological and psychological dysfunctions.
authors.affiliation: Metabolism and Genetics Group, Faculty of Pharmacy, iMed.UL-Research Institute for Medicines and Pharmaceutical Sciences,University of Lisbon, Portugal. iarivera@ff.ul.pt
authors.forename: Isabel
authors.initials: I
authors.lastname: Rivera
authors.forename: Dina
authors.initials: D
authors.lastname: Mendes
authors.forename: Ângela
authors.initials: Â
authors.lastname: Afonso
authors.forename: Madalena
authors.initials: M
authors.lastname: Barroso
authors.forename: Ruben
authors.initials: R
authors.lastname: Ramos
authors.forename: Patrícia
authors.initials: P
authors.lastname: Janeiro
authors.forename: Anabela
authors.initials: A
authors.lastname: Oliveira
authors.forename: Ana
authors.initials: A
authors.lastname: Gaspar
authors.forename: Isabel
authors.initials: I
authors.lastname: Tavares de Almeida
mesh_terms: D001708:Biopterins / Q000031:analogs & derivatives* / Q000627:therapeutic use; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D056726:Genetic Association Studies; D006239:Haplotypes; D006801:Humans; D017720:Molecular Epidemiology; D010641:Phenotype; D010651:Phenylalanine Hydroxylase / Q000172:deficiency* / Q000235:genetics*; D010661:Phenylketonurias / Q000188:drug therapy / Q000201:enzymology / Q000453:epidemiology* / Q000235:genetics*; D011174:Portugal / Q000453:epidemiology
chemical_list: D001708:Biopterins; D010651:Phenylalanine Hydroxylase; C003402:sapropterin