Mutational Spectrum Of Phenylalanine Hydroxylase Gene In Lianyungang Patients With Phenylketonuria

Objective: Phenylketonuria(PKU)is a kind of metabolic disease having hereditary property.The cause of PKU is the change of phenylalanine hydroxylase(PAH)in the body cause the decrease or disappear of PAH activity,which causes the abnormal metabolism of phenylalanine in the liver.Mutations of PAH gene often cause PKU.In China,the incidence of PKU in China is 1/11144 with the analysis on more than 5.8 million newborn data.PAH plays a key role in the conversion of phenylalanine into tyrosine,and affects the normal metabolic rate of phenylalanine in the body.It is located in chromosome 12q23.2 and has 13 exons.Some study on PKU patients showed there were about 700 locus of gene mutationand 67% were missense gene.The locus of gene mutation often leads to the lack of PAH,which cause the change of PKU phenotype.In Lianyungang area,life is backward and the economy is poor.Even if PKU is diagnosed,the treatment rate is poor,and many patients suffer from low intelligence or high phenylalanine due to delayed treatment.Exploring the type of gene mutation in PKU population can help reduce the birth rate of children with PKU and optimize the birth of population.In this paper,we selected Lianyungang patients with PKU and analyzed the distribution characteristics of PAH gene mutation,and obtained the region and location of hot spot mutations,which is of great significance to lay a foundation for prenatal diagnosis,treatment,genetic counseling,prenatal and postnatal care for PKU patients in Lianyungang area.Material and methods: A total number of 40 cases LianyungangPKU families in neonatal screening center of Lianyungang maternal and child health care hospitalwere recruitedfrom January 2009 to June 2015.These families are all ethnic Hanand there is no kinship with each other.First,13 pairs of primers were designed and amplified by PCR,and the primers included 13 exons of PAH gene,some promoter region,and exon and intron junction.Secondly,the PCR products were screened the locus of mutation by Sanger sequencing and the DNA sequence of the parents of the patients in the site was determined.The types and mutation rates of PAH genes in Tianjin,Shaanxi,Beijing,Xinjiang,Shanxi,Qinghai,Gansu,Handan and Suzhou,and compared with Lianyungang region.Results: In forty PKU families,there had 74 mutations in the 80 PAH alleles,which accounting for 92.5%.There were 35 patients with double allele mutation,and the single allele heterozygous mutation was 5,and one was not detected with the allele mutation.A total of 26 patients with complex heterozygous mutations were detected,and the homozygous mutation was 9,the single heterozygous mutation was 5.DHA sequences of parents with mutation sites were determined and there were two families had new mutations.Moreover,the identification was biological and the mutation sites in the other family were inherited from the parents.There were 11 PAH mutations in 40 PKU families,covering 24 types and they were: 11 missense mutations(45.8%),9 splicing mutation(37.5%),3 nonsense mutation(12.5%)and 1 deletion mutation(4.2%).R243Q(14.86%)was the highest frequency in 74 alleles,and then R111X(12.16%),R241C(10.80%),IVS2+5G>T(9.46%),V399V(8.10%),Y356X(6.75%),EX6-96A>G(5.40%),IVS7-1G>A(5.40%)and IVS7+2T>A(4.05%).The relative frequency of R243 Q in Lianyungang area is higher than that in Shanxi Province,and significantly lower than Shaanxi,Beijing,Xinjiang,Qinghai,Gansu and Handan 6 districts(P<0.05 或 P<0.01),and there is no significant difference between Tianjin and Suzhou.The detection rate of R111 X mutation in Lianyungang region was significantly higher than that of Shaanxi,Beijing,Xinjiang,Shanxi,Qinghai,Gansu,Handan and Suzhou.Conclusions: PAH gene mutations in PKU patients in Lianyungang region carry significant hotspot mutations R243Q(14.86%)、R111X(12.16%)andR241C(10.80%)PAH genes in the region are similar to those in some northern regions.Compared with the southern cities,Japan,the United States and other foreign regions,the difference is larger.It is concluded that the PAH gene mutation in Lianyungang region is more complex and presents various characteristics.