Phenylketonuria Gene Mutations In Zhejiang Province

IntroductionPhenylketonuria (PKU), a common inborn errors of metabolism, is caused by deficiency of the hepatic enzyme phenylalanine hydroxylase. The biochemical characteristic of this disease is an elevated concentration of L-phenylalanine in blood serum. PKU is caused by mutations in the 13 exon PAH gene spanning about 90 kbp on chromosome 12q22-q24.1. More than 500 PKU gene mutations in different populations have been identified until now. These mutations show a non-randomly geographical and ethnical distributions, with a different spectrum observed in the Caucasian and Asian populations. The PKU-associated hyperphenylalaninemia phenotype is highly variable, primarily due to a great allelic heterogeneity at the PAH locus. The severity of the neonatal PKU can be predicted on the patients genotypes and the knowledge of its correlation with the clinical phenotype. In the present study, we evaluated 26 PKU children in Zhejiang province, China. Genetic analysis was performed to determine the PAH mutation types, and the phenotype/genotype relationship is of great help to early diagnosis and treatment in children with PKU.MethodsA total of 26 children, born between 1999 and 2006, were diagnosed as PKU at the Neonatal Screening Center of Zhenjiang Province. Meanwhile, 60 normal children are served as the controls. Blood samples (2ml) from each subject are collected and anti-coagulated with EDTA. Genome DNA extraction was performed. The coding region of the PAH gene was amplified by polymerase chain reaction (PCR) and sequenced.Results(1) A total of 17 heterozygous mutations including 11 missense mutations (R165D, R169S, Y204C, F240S, R243Q, R252Q, G257V, R261Q, R408W, R408Q, R413P) , 2 nonsense mutations (R111X, Y356X) , 4 splice junction mutations(IVS4nt+47C→T, IVS4nt-1G→A, IVS7nt+2T→A, IVS10nt+39G→T) were detected.(2) Five single nucleotide polymorphisms ( Q232Q, V245V, IVS9nt+43G → T, IVS10nt+97G→A, L385L) were found in this study.(3) Three novel mutations were identified in this study: IVS10nt+39G → T, IVS9nt+43G→T and IVS10nt+97G→A.(4) There is a good correlation between biochemical phenotype and genotype.Conclusions1 .We obtained the spectrum of Zhejiang Province PAH mutations. 22 mutations were found in this study in which R111X, IVS4nt-1G→A and F240S were the hotspots mutations, their frequency were 9.6%.2.We found 3 novel mutations, which expand the spectrum of Chinese PAH mutations. 3.The consistency between the biochemical phenotype and the genotype provides theoretic references for optimal dietary therapy and prognosis at clinic.