OBJECTIVETo obtain the mutation spectrum of exon 12 of the phenylalanine hydroxylase(PAH) gene.

METHODSThe samples from 127 patients with phenylketonuria(PKU) were studied by polymerase chain reaction(PCR)-single strand conformation polymorphism(SSCP) PCR-denaturing gradient gel electrophoresis(DGGE) and direct DNA sequencing.

RESULTSFour heterozygous mutations including R413P S411X R408W R408Q in 10 of 127 patients were identified by DNA sequencing. The frequencies of R413P S411X R408W R408Q mutation were 2.76%, 0.39%, 0.39% and 0.39%, respectively. The S411X mutation in Chinese was first reported. Only 2 cases with R413P mutation were detected by SSCP. DGGE analysis showed that 10 cases displayed 3 kinds of abnormal electrophoretic bands. There were no obvious differences in the frequency of R413P mutation between northern and southern Chinese with PKU, and between classical PKU and hyperphenylalaninemia.

CONCLUSIONDGGE is more sensitive than SSCP in screening the mutations of exon 12 of the PAH gene. DGGE combined with DNA sequencing can be used to define all the mutations of exon 12 of the PAH gene. These results indicate the similarity in the frequency of R413P mutation between northern and southern patients.