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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
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ABSTRACT Phenylketonuria (PKU; MIM 261600) is an autosomal recessive metabolic disorder caused by a deficiency of phenylalanine hydroxylase (PAH; EC 1.14.16.1). 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.

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    • "Nevertheless, in many of these studies, the mutant genotype has remained partially or completely undetermined in about less than 10% of patients (Mirisola et al., 2001). In recent years, several studies (Gable et al., 2003; Desviat et al., 2006; Kozak et al., 2006; Birk Moller et al., 2007; Lee et al., 2008) have shown that a significant proportion of these undetermined alleles consist of large deletions overlapping one or more exons. These deletions have been difficult to detect in compound heterozygotes using conventional gene-scanning methods (e.g. "
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