Mutation analysis of PAH gene in patients with PKU in western Iran and its association with polymorphisms: identification of four novel mutations.

Phenylketonuria (PKU) is an autosomal recessive disorder characterized by a mutation in the phenylalanine hydroxylase (PAH) gene. Untreated PKU can lead to mental retardation, seizures, and other serious medical problems. This study was designed to investigate the status of molecular defects in the PAH gene and their association with polymorphisms in Kurdish patients with PKU in the Kermanshah province, western Iran. The study was conducted on 27 unrelated patients with PKU over a 2-year period (from 2010 to 2012). All 13 exons plus exon-intron boundaries of the PAH gene were analyzed and we identified 15 different mutations, including two novel mutations, in 51 of the 54 mutant alleles (diagnostic efficiency of 94.4 %). IVS4 + 1G > C (c.441 + 1G > C) and IVS7 - 5 T > C (c.843 - 5 T > C) are novel mutations that have not been reported in the academic literature or the PAH locus database ( http://www.pahdb.mcgill.ca ); therefore, they may be specific to the Kurdish population. IVS2 + 5G > C and IVS9 + 5G > A were the two most prevalent mutations in our sample, with frequencies of 26 % and 17 %, respectively. The second most common mutations were p.R261X, IVS10 - 11G > A, p.K363 > Nfs and IVS7 - 5 T > C, with each showing a relative frequency of 7.4 %. All other detected mutations, including p.F55 > Lfs, p.R176X, p.R243Q, p.V230I, p.R243X, p.R261Q, IVS8 - 7A > G and p.E390G had frequencies of less than 4 %. The present study showed that there is a distinct difference in the characteristics of PAH mutations between the Kermanshah province and other parts of Iran, suggesting that Kermanshah may have a unique population distribution of PAH gene mutations. Iran lies on the route of major ancient movements of the Caucasian people toward the Mediterranean basin, and Kermanshah has previously been called the gateway to Asia. Most of the mutations identified in this study are common in the Mediterranean region. Therefore, our findings are consistent with the historical and geographical links between the Iranian population and the populations of Mediterranean region.

The proportion of tetrahydrobiopterin deficiency and PAH gene deficiency variants among cases with hyperphenyalaninemia in Western Iran.

BACKGROUND: Defects either in phenylalanine hydroxylase (PheOH) or in the production and recycling of its cofactor (tetrahydrobiopterin [BH4]) are the causes of primary hyperphenylalaninemia (HPA). The aim of our study was to investigate the current status of different variants of HPA Kurdish patients in Kermanshah province, Iran. MATERIALS AND METHODS: From 33 cases enrolled in our study, 32 were identified as HPA patients. Reassessing of pre-treatment phenylalanine concentrations and the analysis of urinary pterins was done by high-performance liquid chromatography method. RESULTS: A total of 30 patients showed PAH deficiency and two patients were diagnosed with BH4 deficiency (BH4/HPA ratio = 6.25%). Both of these two BH4-deficient patients were assigned to severe variant of dihydropteridine reductase (DHPR) deficiency. More than 75% of patients with PAH deficiency classified as classic phenylketonuria (PKU) according their levels of pre-treatment phenylalanine concentrations. CONCLUSION: Based on the performed study, we think that the frequency of milder forms of PKU is higher than those was estimated before and/or our findings here. Furthermore, the frequency of DHPR deficiency seems to be relatively high in our province. Since the clinical symptoms of DHPR deficiency are confusingly similar to that of classic PKU and its prognosis are much worse than classical PKU and cannot be solely treated with the PKU regime, our pilot study support that it is crucial to set up screening for BH4 deficiency, along with PAH deficiency, among all HPA patients diagnosed with HPA.

Molecular analysis of exons 6 and 7 of phenylalanine hydroxylase gene mutations in Phenylketonuria patients in Western Iran.

BACKGROUND: Phenylketonuria (PKU) is an inborn error of amino acid metabolism that results from a deficiency of phenylalanine hydroxylase (PAH). According to PAH database, exons 6 and 7 and their flanking introns of PAH gene contain the greatest number of mutant alleles. Therefore, as a preliminary study, nucleotide sequence analysis of exons 6 and 7 of the PAH gene has been performed in 25 PKU patients whose ancestors lived in Kermanshah province of Iran. To date, there has been no mutation data describing the genotypes of the PKU disease in this Kurdish ethnic region background. MATERIALS AND METHODS: Twenty-five patients (aged between 2 and 23 years) participated in this study. The DNA fragments containing two exons of the PAH gene [6 and 7] and their exon-flanking intronic sequences were amplified and sequenced. RESULTS: The total of detected mutations were R261X (8%), R176X (4%), R243Q (4%), R243X (2%) and R261Q (2%), as they accounted for 20% of all mutant alleles in this study. The identified polymorphisms are: IVS5 -54 G > A (22%), Q232Q (8%) and V245V (4%). All of the detected mutations in this study are related to CpG dinucleotides in the PAH gene sequence. CONCLUSION: The frequency of R261X, the most common mutation in our study, in Iranian population is <5%. Furthermore, there is no report of detection of R176X and R243Q in Isfahan and Azeri Turkish populations. These findings confirm the common Mediterranean mutations in this local population, although with more or lower frequencies than those reported in other related studies in Iran. Therefore, it may be necessary to study the PAH gene mutations in other provinces of Iran separately.