Mutational spectrum of phenylalanine hydroxylase gene in Ningxia patients with phenylketonuria

Abstract

Objective To analyze the mutation distribution of phenylalanine hydroxylase(PAH) gene in patients with phenylketonuria(PKU) in Ningxia, and understand the hot spots and regions of PAH gene. Methods Firstly, 6 hot mutation exons including 3, 5, 6, 7, 11, 12 and their surrounding introns of the PAH gene in 30 patients with PKU in Ningxia were directly sequenced.And then the last 7 exons of 1, 2, 4, 8, 9, 10, 13 were sequenced for the patients in which 2 mutant alleles were not characterized.Multiplex ligation-dependent probe amplification(MLPA) was performed for the identification of uncharacterized mutant alleles after PAH sequence analysis of patients with PKU. Results Among 60 alleles, there were 58 mutant alleles(96.7%). Forty-six (81.6%) mutant alleles were found in the exons 3, 5, 6, 7, 11, 12.A total of 23 various mutations were detected, including missense(n=9), splicing(n=9), nonsense(n=2), small deletion(n=2) and large deletion(n=1). The most common mutations were R243Q(18.3%), IVS4-1G>A(11.7%) and R111X(11.7%). Among them, a novel mutation N393del was detected in exon 11.MLPA identified a large deletion(c.-1932_+ 3402del) in 3 patients, 1 of them was homoallelic mutation, and the others were heteroallelic mutation. Conclusions There are obvious hotspots and hot spot areas of PAH gene in PKU patients in Ningxia.There is a large deletion mutation in PKU patients in Ningxia.The MLPA is an effective assay to detect large deletion in PAH gene. Key words: Phenylketonuria; Phenylalanine hydroxylase; Gene sequencing; Multiplex ligation-dependent probe amplification; Ningxia