Mutation Spectrum Of Phenylalanine Hydroxylase Gene Research Articles

Mutation spectrum of PAH gene in phenylketonuria patients in Northwest China: identification of twenty novel variants.

This study was performed to analyze the mutational spectrum of the phenylalanine hydroxylase (PAH) gene in phenylketonuria (PKU) patients in Northwest China, to identify mutational hot spots, and to determine the correlation between variants and clinical phenotypes of PKU. A large cohort of 475 PKU families in Northwest China was enrolled to analyze PAH gene variants using Sanger sequencing, Multiplex ligation-dependent probe amplification (MLPA), and gap-PCR. Bioinformatics software was used to predict the pathogenicity of novel variants and analyze the correlations between PAH gene variants and phenotypes of PKU patients. A total of 895 variants were detected in the 950 alleles of 475 patients with PKU (detection rate: 94.21%), 20 of which were novel variants. Other 108, previously known variants, were also identified, with the three most frequent variants being p.Arg243Gln (14.00%), c.611A > G (5.58%), and p.Tyr356* (4.95%). Seven different large deletion/duplication variants were identified by the MLPA method, including the large deletion c.-4163_-406del3758 with high frequency. A correlation analysis between patient phenotype and gene variant frequency showed that p.Arg53His and p.Gln419Arg were correlated with mild hyperphenylalaninemia (MHP). In conclusion, the mutational spectrum underlying PKU in Northwest China was established for the first time. Functional analysis of 20 novel PAH gene variants enriched the PAH gene mutational spectrum. Correlation analysis between variants frequencies in compound heterozygous patients and phenotype severity is helpful for phenotypic prediction.

Genotype and phenotype correlation of phenylalanine hydroxylase deficiency among patients from Henan

To delineate the mutation spectrum of phenylalanine hydroxylase (PAH) gene among patients affected with phenylalanine hydroxylase deficiency (PAHD) in Henan Province of China, and to explore the correlation between the genotype and the phenotype. A total of 155 affected children were recruited. Potential mutation of the PAH gene were analyzed by direct sequencing. The genotype-phenotype correlation was analyzed by matching the expected and observed phenotypes. Over 72 mutations and 108 genotypes have been identified. There were 7 homozygous mutations, including 1 case with EX6-96A>G/EX6-96A>G, 1 with R241C/R241C, 1 with R413P/R413P, and 4 with R243Q/R243Q. Among these, 6 patients have presented classic PKU phenotypes, except for a R241C/R241C genotype which has led to mild PKU. In 104 patients carrying compound PAH mutations, 52 were classic, 34 were mild and 39 had mild HPA. Patients who were heterozygous for EX6-96A>G/R241C, R243Q/A434D, EX6-96A>G/R413P and EX6-96A>G/ R241C were found with both the classic PKU and mild PKU phenotypes. Common mutations associated with mild HPA have included R53H, R243Q, V399V and H107R. The common mutations associated with mild PKU included R243Q, R241C, EX6-96A>G, and IVS4-1G>A. The prevalent mutations in classic PKU were R243Q, EX6-96A>G and V399V. The consistency between prediction of the biochemical genotype and observed phenotype was 77.78%, especially in classic PKU, the consistency was up to 82.14%. Significant correlations were disclosed between pretreatment levels of phenylalanine and AV sum (r=-0.6729, P < 0.01). The mutation spectrum of PAH gene in Henan seems to differ from that of other regions. Independent assortment of mutant alleles may result in a complex genotype-phenotype correlation, but the genotypes of PAHD patients have correlated with the phenotype.

Neonatal hyperphenylalaninemia screening from 1985 to 2012 in Nanjing: a retrospective analysis of 27 years

Objective To explore the incidence,classification,treatment and prognosis of neonatal hyperphenylalaninemia(HPA) in Nanjing.Methods Infants born from September 1st,1985 to September 1st,2012 in Nanjing were investigated.Heel blood samples of neonates were collected at 72 hours after birth,and the concentration of blood phenylalanine was determined by fluorescent quantitative method in Nanjing Neonatal Screening Center within 20 days after birth.The deferential diagnosis was performed in all 81 cases diagnosed as HPA by tetrahydrobiopterin loading test,urinary pterin analysis and dihydropteridine reductase activity determination.The blood phenylalanine concentration and mental development were followed up regularly on infants with HPA.Mutations of phenylalanine hydroxylase (PAH) gene were analyzed by gene sequencing in 20 patients with PAH deficiency.The relationship between phenylalanine concentration and mental development was analyzed by variance analysis,LSD and Pearson correlation analysis.Results (1) The incidence of HPA in neonates in Nanjing was 1/8800(81/712 818).Among 81 confirmed cases,78 cases (96.3％) suffered from PAH deficiency,including 37 classical phenylketonurias (PKU),23 mild PKU and 18 mild HPA; the three patients (3.7％) with tetrahydrobiopterin deficiency were all 6-pyruvoyl tetrahydropterin synthase deficiency.(2) Among these 81 cases,eight refused to any treatment (two of them died),six had mental retardation (one with epilepsy),and six were lost in follow-up.For the rest 67 patients who received medical treatment,the ages at the last visit were three months to 26 years old.Among the 55 patients who received mental development evaluation,five of them were abnormal [intelligence quotient (IQ)＜75].(3) Negative correlation was observed between IQ and the average concentration of phenylalanine(r=-0.53,P＜0.05),while no correlation between IQ and the initial concentration of phenylalanine was observed (r =-0.39,P＞0.05).(4)Among the 20 patients with PAH deficiency who were tested for gene sequencing,18 mutations of PAHgenewere detected.The most common mutation were EX6-96A＞G and R241C(34.28％).Conclusions The incidence of HPA in Nanjing was higher than the average national level.With early diagnosis and standard treatment,over 90％ of HPA patients could have normal mental development.The mutation spectrum of PAH gene of Nanjing population is different from other areas,and the most common mutations of PAH gene are EX6-96A＞G and R241C. Key words: Phenylketonurias; phenylalanine hydroxylase; Mutation; Neonatal screening; Retrospective studies

Mutation spectrum in Taiwanese patients with phenylalanine hydroxylase deficiency and a founder effect for the R241C mutation.

The spectrum of phenylalanine hydroxylase (PAH) gene mutations was determined in 25 families of hyperphenylalaninemia identified by a neonatal screening program in Taiwan. The coding sequence and exon-flanking intron sequences of PAH gene were amplified and sequenced. Mutations were identified in forty-five of the 50 chromosomes. R241C was the most common mutation (36% of the chromosomes), followed by R408Q (14% of the chromosomes). The remaining mutations were rare and seven mutations have not been reported before: p.F233L (c.697T>C), p.R252Q (c.756G>A), p.E286K (c.856G>A), p.G312V (c.935G>T), p.P314T (c.940C>A), p.I95del (c.284_286delTCA), and p.T81fsX6 (c.241_256del). Both p.R241C and p.R408Q are classified as mild phenylketonuria (PKU) or mild hyperphenylalaninemia (MHP) mutation, which may explain the fact that classical PKU is very rare in Taiwan (n=4, or one in 413,035). This strong founder effect for the p.R241C mutation has been described neither in the Caucasian populations, nor in other reports from Chinese. Since most of the populations in Taiwan are derived from Southeastern China, the spectrum of PAH gene mutations in Southeastern China should be different from other Chinese populations. This report not only disclose a specific spectrum of PAH gene mutation in Taiwan, but may also give clues to the movement of populations in Mainland China.