Characteristics of phenylalanine hydroxylase gene mutations in children with phenylketonuria in Suzhou, Jiangsu Province

Abstract

Objective To study the characteristics of phenylalanine hydroxylase(PAH) gene mutations in children with phenylketonuria(PKU) in Suzhou, Jiangsu Province. Methods From 2008 to 2011, a total of 25 cases PKU children in Suzhou, Jiangsu Province, who were confirmed genotyping by tandem mass spectrometry, phenylalanine loading test and uropterin test with their blood sample in Shanghai Xinhua Hospital, and their parents were all enrolled as the research objects.Mutations in PAH gene of 25 children with PKU and their parents were detected by SNaPShot genotyping technology and next generation sequencing(NGS) technology.The results of genotypes by these two technology were verified by Sanger sequencing.The characteristics of PAH gene mutations of PAH gene in children with PKU in Suzhou, Jiangsu Province were analyzed. The study protocol was approved by the Ethical Review Board of Investigation in Human Being of Nanjing Medical University Affiliated Suzhou Municipal Hospital. Informed consent was obtained from the parents of each participating child. Results The results of PAH gene mutations in the subjects by SNaPShot genotyping and NGS technology were coincide with the Sanger squencing results.Using SNaPShot genotyping technology, 9 kinds of mutations of PAH gene in 25 children with PKU could be detected, which including Exon7-R243Q, Exon6-Y204X, Exon7-R241C, Exon5-IVS4-1, Exon12-R413P, Exon3-R111X, Exon7-R261Q, Exon10-W326X and Exon11-Y356X, and PAH gene mutations detection rate was 58.0%(29/50). Ten of 25 children with PKU carrying PAH gene homozygous mutations or compound heterozygous mutations could be detected by SNaPShot genotyping technology, and pedigree analysis can confirm 100% genetic diagnosis information.Another 15 of 25 children with PKU tested by SNaPShot genotyping technology carrying one PAH gene heterozygous mutation or not, were further tested by NGS technology, and 12 of 15 children could be detected carrying PAH gene compound heterozygous mutations, but another 3 of 15 children, only could be detected carrying PAH gene heterozygous mutation.Other 15 kinds of mutations were detected by NGS technology, including A434D、V399V and Y325X, with 4.0% mutation frequency.The PAH gene total mutation detection rate of combined SNaPShot genotyping and NGS technology was 94.0%(47/50). Conclusions The hot spot mutations in PAH gene of children with PKU in Suzhou, Jiangsu Province included R243Q, Y204X, R241C, IVS4-1, R413P, R111X, A434D, V399V and Y325X.Testing PAH gene mutations by SNaPShot genotyping technology is a helpful method to gene diagnosis of PKU. Key words: Phenylketonuria; Phenylalanine hydroxylase; Point mutation; Genotyping techniques