MISSENSE MUTATIONS ASSOCIATED WITH RFLP HAPLOTYPE-1 AND HAPLOTYPE-4 OF THE HUMAN PHENYLALANINE-HYDROXYLASE GENE

  • 1 January 1990
    • journal article
    • research article
    • Vol. 46  (1) , 18-25
Abstract
We report missense mutations associated with haplotype 1 and haplotype 4 alleles of the human phenylalanine hydroxylase (PAH) gene. Individual exon-containing regions were amplified by polymerase chain reaction from genomic DNA of a PKU patients who was a haplotype 1/4 compound heterozygote. The amplified DNA fragments were subcloned into M13 for sequence analysis. Missense mutations were observed in exons 5 and 7, resutling in the substitution of Arg by Gln at residues 158 and 261 and the enzyme, respectively. Expression analysis in heterozygous mammalian cells after site-directed mutagenesis demonstrated that the Arg158-to-Gln158 mutation is a PKU mutation, whereas the Arg261-to-Gln261 mutation is apparently silent in the assay system. Hybridization analysis using allele-specific oligonucleotide probes demonstrated that the Arg158-to-Gln158 mutation is present in two of six mutant haplotype 4 alleles among the Swiss and constitutes about 40% of all mutant haplotype 4 allleles in the European population. The mutation is not present in normal alleles or in any mutant alleles of other haplotypes. The results provide conclusive evidence that there is linkage disequeilibrium between mutation and haplotype in the PAH gene and that multiple have occurred in the PAH gene of a prevalent haplotype among Caucasians.