Molecular epidemiology and BH4-responsiveness in patients with phenylalanine hydroxylase deficiency from Galicia region of Spain M.L. Couce a, ⁎, M.D. Bóveda a , A. Fernández-Marmiesse a , A. Mirás a , B. Pérez b , L.R. Desviat b , J.M. Fraga a a Unit of Diagnosis and Treatment of Congenital Metabolic Diseases, Department of Pediatrics, Hospital Clinico Universitario de Santiago, Santiago de Compostela, Spain b Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular Severo Ochoa CSIC-UAM, CIBERER, IdiPaz, Madrid, Spain abstract article info Article history: Accepted 1 March 2013 Available online 14 March 2013 Keywords: BH4-responsiveness Hyperphenylalaninemia molecular epidemiology PAH mutation Phenylketonuria Knowledge of hyperphenylalaninemia (HPA) mutational spectrum in a population allows in many cases an accurate prediction of the phenotype and tetrahydrobiopterin (BH4) responsiveness, thus selecting an ade- quate treatment. In this work, we have performed the molecular characterization of 105 HPA patients from Galicia, in the northwest region of Spain, evaluating their phenotype and BH4 response. The mutational spectrum analysis showed 47 distinct mutations in 89 families, 37 of them (78.7%) corre- sponding to missense mutations. Six mutations account for 47.2% of all the investigated alleles, each one with a frequency ≥ 5% (IVS10-11G>A, p.R261Q, p.V388M, p.R176L, p.E280K, p.A300S). The most prevalent HPA mutations in Galicia are the common Mediterranean mutation IVS10-11G>A and p.R261Q, with fre- quencies of 13.8% and 10.5%, respectively. One novel mutation (p.K361Q; c.1081A>C) was also reported. Al- though a good genotype–phenotype correlation is observed, there is no exact correlation for some genotypes involving mutations p.R261Q, p.I65T or IVS10-11G>A. Forty seven patients were monitored for post-challenge BH4, establishing genotype-based predictions of BH4-responsiveness in all of them. All phenylketonuric patients with 2 nonresponsive mutations were unresponsive to BH4 and patients with mutations previously associated with BH 4 responsiveness in the two alleles had a clear positive response to the test, with the exception of 5 patients with mutations p.R261Q, p.I65T and p.R68S. Our study supports a similar degree of heterogeneity of the HPA mutation spectrum in Galicia compared to reported data from Southern Europe. Patients carrying null mutations in both alleles showed the highest de- gree of concordance with the most severe phenotypes. Genotype is a good predictor of BH4 response. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Deficiency of the hepatic enzyme phenylalanine hydroxylase (PAH; E.C.1.14.16.1) causes phenylketonuria (PKU; OMIM 261600), which is the most frequent inborn error of amino acid metabolism in Caucasians with a prevalence of 1 in 10,000 individuals, corre- sponding to a carrier frequency of about 1 in 50 (Blau and van Spronsen, 2010; Mathias and Bickel, 1986). The PAH gene (NM_000277.1) has been mapped to the 12q22-24.2 locus, covers 100 kb of genomic DNA and is structured in 13 exons sep- arated by introns. Thus far, more than 700 mutations and sequence var- iants are listed in the PAH Mutation Analysis Consortium Database (http://www.pahdb.mcgill.ca). Approximately 60% of these molecular defects are missense mutations, 11% are splicing mutations, 5.7% non- sense mutations, 13% small deletions and 1.8% small insertions (Blau et al., 2011; Scriver et al., 2003; Sterl et al., 2013). Large deletions are generally rare (Moller and Nygren, 2007). A systematic review of PKU in Europe identified 29 mutations that may be regarded as prevalent in European populations (Zschocke, 2003). There are marked differences in the spectrum of mutations between different populations. In most Central and Northern European countries 3–5 mutations account for more than 50% of the mutant alleles in the population (Sterl et al., 2013; Zschocke, 2003). A greater degree of heterogeneity is shown in Southern Europe (Daniele et al., 2006; Desviat et al., 1999; Pérez et al., 1997; Rivera et al., 2011). Most individuals affected with PKU are compound heterozygotes carrying different mutations on both alleles. Knowledge of the func- tional effects of the mutations allows prediction of the likely residual enzyme function, but there are still unknown factors that influence the phenotype (Gulderberg et al., 1998; Kayaalp et al., 1997). PAH deficiency is associated with a wide range of phenotypes for which Gene 521 (2013) 100–104 Abbreviations: HPA, hyperphenylalaninemia; Phe, phenylalanine; PAH, phenylala- nine hydroxylase; PKU, phenylketonuria; BH4, tetrahydrobiopterin. ⁎ Corresponding author at: Unit of Diagnosis and Treatment of Congenital Metabolic Diseases, Department of Pediatrics, Hospital Clinico Universitario de Santiago, Travesía da Choupana s/n, 15706 Santiago de Compostela, A Coruña, Spain. Tel.: +34 981950167; fax: +34 981951135. E-mail address: maria.luz.couce.pico@sergas.es (M.L. Couce). 0378-1119/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gene.2013.03.004 Contents lists available at SciVerse ScienceDirect Gene journal homepage: www.elsevier.com/locate/gene