Mutation analysis of PAH gene and characterization of a recurrent deletion mutation in Korean patients with phenylketonuria.

Department of Laboratory Medicine and Genetics, Soonchunhyang University Bucheon Hospital, Soonchunhyang Univerisity College of Medicine, Bucheon 420-767, Korea.
Experimental and Molecular Medicine (Impact Factor: 2.46). 11/2008; 40(5):533-40. DOI: 10.3858/emm.2008.40.5.533
Source: PubMed

ABSTRACT Phenylketonuria (PKU; MIM 261600) is an autosomal recessive metabolic disorder caused by a deficiency of phenylalanine hydroxylase (PAH; EC Point mutations in the PAH gene are known to cause PKU in various ethnic groups, and large deletions or duplications account for up to 3% of the PAH mutations in some ethnic groups. However, a previous study could not identify approximately 14% of the mutant alleles by sequence analysis in Korean patients with PKU, which suggests that large deletions or duplication might be frequent causes of PKU in Koreans. To test this hypothesis, we performed multiplex ligation-dependent probe amplification (MLPA) for the identification of uncharacterized mutant alleles after PAH sequence analysis of 33 unrelated Korean patients with PKU. Bi-directional sequencing of the PAH exons and flanking intronic regions revealed 27 different mutations, including four novel mutations (two missense and two deletion mutations), comprising 57/66 (86%) mutant alleles. MLPA identified a large deletion that encompassed exons 5 and 6 in four patients, another large deletion that extended from exon 4 to exon 7 in one patient, and a duplication of exon 4 in one patient. Chromosomal walking characterized the deletion breakpoint of the most common large deletion that involved exons 5 and 6 (c.456_706+138del). The present study shows that the allelic frequency of exon deletion or duplication is 9% (6/66) in Korean PKU patients, which suggests that these mutations may be frequent causes of PKU in Korean subjects.

  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the results of a molecular genetic study on the phenylalanine hydroxylase (PAH) gene among phenylketonuria (PKU) patients and their family members residing in Kemerovo oblast and the Sakha Republic. To reveal the PAH gene mutations, the researchers applied exon amplification and a direct determination of their nucleotide sequences. The study has revealed both well-known mutations (R158Q, R252W, R261Q, P281L, IVS10 − 11G > A, R408W, and IVS12 + 1G > A) and some rarely encountered ones (IVS2 + 5G > A, R155H, Y168H, W187R, E221-D222 > Efs, A342T, Y386C, and IVS11 + 1G > C). Some of the studied populations with a mixed ethnic ancestry have been shown to demonstrate a wider spectrum of their PKU-associated alleles.
    Cytology and Genetics 07/2012; 46(4). DOI:10.3103/S0095452712040032 · 0.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Frameshift mutation p.G352fsdelG in the PAH gene was recently reported as the most common mutation in Moroccan patients with phenylketonuria (PKU). This result, if confirmed, would considerably facilitate genetic counseling and molecular diagnosis of the disease in Morocco. Given that the incidence of PKU in the Mediterranean region is estimated at between 1/4000 and 1/10,000, this mutation would be harbored by many Moroccans. We aimed to estimate the frequency of heterozygotes for the p.G352fsdelG mutation in Moroccan newborns. In this study, we used a reliable TaqMan(®) real-time polymerase chain reaction to detect the mutation p.G352fsdelG in the PAH gene in 250 unrelated Moroccan newborns. DNA was extracted from umbilical cord blood with maternal consent. The supposed recurrent mutation p.G352fsdelG was found in none of the 250 tested newborns. Therefore, the frequency of heterozygotes for this mutation would be less than 1/250, and the incidence of patients with PKU homozygous for this mutation would not exceed 1/100,000. The p.G352fsdelG mutation in the PAH gene does not appear to be prevalent in the Moroccan population and would be responsible for only few cases of PKU. The previous report of this anomaly as being responsible for 62.5% of PKU patients in Morocco could be explained by selection bias.
    Genetic Testing and Molecular Biomarkers 07/2012; 16(8):996-8. DOI:10.1089/gtmb.2012.0011 · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Multiplex ligation-dependent probe amplification (MLPA) has become a standard method for identifying copy number mutations in diagnostic and research settings. The occurrence of false-positive deletion findings and the underlying causes are well recognized, whereas false-positive duplication/amplification findings have not been appreciated so far. We here present three pertinent cases which were only identified on extended, nonstandard secondary analyses. We also offer and experimentally validate a potential explanation. Our findings imply that MLPA data indicating gain of genomic sequence require validation on an independent sample or by an independent method.
    Analytical Biochemistry 02/2012; 421(2):799-801. DOI:10.1016/j.ab.2011.12.002 · 2.31 Impact Factor