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Articles |
1
The John F. Kennedy Institute, Gl. Landevej 7, 2600 Glostrup, Denmark.
2
Division of Clinical Chemistry and Biochemistry,
University Childrens Hospital, Steinwiesstrasse 75, 8032 Zurich,
Switzerland.
a Author for correspondence. Fax 45-4343-1130; e-mail flg{at}kennedy.dk
Background: Deficiency of 6-pyruvoyltetrahydropterin synthase (PTPS) is a recessively inherited disorder that leads to depletion of 5,6,7,8-tetrahydrobiopterin, the obligatory cofactor for hydroxylation of phenylalanine, tyrosine, and tryptophan. A marker for neonatal detection of PTPS deficiency is hyperphenylalaninemia (HPA). Molecular analysis would provide a simple and reliable means for distinguishing PTPS deficiency from other potential causes of HPA.
Methods: We developed a method based on PCR in combination with denaturing gradient gel electrophoresis (DGGE) that rapidly scans the six coding sequences and all splice sites of the PTPS gene (PTS) for mutations. This method was used to examine the status of the PTS gene in control samples with known PTS mutations and in five patients with PTPS deficiency.
Results: Two features of the PTS gene posed
particular problems in relation to DGGE analysis: the very high GC
content of exon 1, and a 15-bp poly(dT) stretch in the acceptor splice
site of intron 1. Both problems were solved by special design of
amplification primers. PCR and DGGE conditions were adjusted to allow
simultaneous analysis of all six regions of the PTS
gene. Using this one-step approach, all control mutations were readily
resolved. Among the five PTPS patients, four mutations were identified,
including IVS1-3C
G, IVS2-7T
A, V57del, and V97M (289G
A). The
IVS1-3C
G mutation was shown by reverse transcription-PCR analysis to
produce multiple splice variants.
Conclusions: We have established a fast and reliable screening method for detection of mutations and small deletions/insertions in the PTS gene. This method should be useful for rapid diagnosis of PTPS deficiency in newborns with HPA.
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