A study on the mutations at the phynylalanine hydroxylase gene among the Japanese population

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Objectives : At least thirty-one mutations at the phenylalanine hydroxylase gene locus have been identified among various ethnic populations. Significant differences in the distribution of such mutations are known among such ethnic populations. This project was designed to elucidate mutations at the phenylalanine hydroxylase gene among the Japanese phenylketonuric and hyperphenylalaninemic patients.Materials and Methods : Three phenylketonurics, one hyperphenylalaninemic patient and two healthy individuals were enrolled in this study. Genomic DNA was extracted from peripheral leukocytes or lymphocytes after proteinase K digestion by phenol extraction. Exons 3 and 5 of the phenylalanine hydroxylase gene were amplified by the polymerase chain reaction technique with the DNA specimens extracted from these individuals as templates. Sequences of primers were as previously described. The amplified exons were cloned and subjected to sequencing by a dideoxy technique.Results : A ^<553>C->T mutation (R111Ter mutation) was found in one allele of one of the phenylketonurics. The mutations at the other allele of this patient and in the other patients have not been identified.Comments : This mutation have been identified among the Chinese phenylketonuric patients, and accordingly is of etiological significance. Analysis of mutations in the other allele of this patient and in the other patient are now in progress.