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This Article Full Text Full Text (PDF) 084434.Supplemental Data All Versions of this Article: clinchem.2006.084434v1 53/7/1216    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Williams, E. Articles by Rumsby, G. Search for Related Content PubMed PubMed Citation Articles by Williams, E. Articles by Rumsby, G. Related Collections Molecular Diagnostics and Genetics

Selected Exonic Sequencing of the AGXT Gene Provides a Genetic Diagnosis in 50% of Patients with Primary Hyperoxaluria Type 1

Clinical Biochemistry, University College London Hospitals, London, United Kingdom.

^aAddress correspondence to this author at: Clinical Biochemistry, 60 Whitfield St., London W1T 4EU, United Kingdom. Fax 44-0-207-380-9584; e-mail gill.rumsby{at}uclh.nhs.uk

Background: Definitive diagnosis of primary hyperoxaluria type 1 (PH1) requires analysis of alanine:glyoxylate aminotransferase (AGT) activity in the liver. We have previously shown that targeted screening for the 3 most common mutations in the AGXT gene (c.33_34insC, c.508G>A, and c.731T>C) can provide a molecular diagnosis in 34.5% of PH1 patients, eliminating the need for a liver biopsy. Having reviewed the distribution of all AGXT mutations, we have evaluated a diagnostic strategy that uses selected exon sequencing for the molecular diagnosis of PH1.

Methods: We sequenced exons 1, 4, and 7 for 300 biopsy-confirmed PH1 patients and expressed the identified missense mutations in vitro.

Results: Our identification of at least 1 mutation in 224 patients (75%) and 2 mutations in 149 patients increased the diagnostic sensitivity to 50%. We detected 29 kinds of sequence changes, 15 of which were novel. Four of these mutations were in exon 1 (c.2_3delinsAT, c.30_32delCC, c.122G>A, c.126delG), 7 were in exon 4 (c.447_454delGCTGCTGT, c.449T>C, c.473C>T, c.481G>A, c.481G>T, c.497T>C, c.424-2A>G), and 4 were in exon 7 (c.725insT, c.737G>A, c.757T>C, c.776 + 1G>A). The missense changes were associated with severely decreased AGT catalytic activity and negative immunoreactivity when expressed in vitro. Missense mutation c.26C>A, previously described as a pathological mutation, had activity similar to that of the wild-type enzyme.

Conclusions: Selective exon sequencing can allow a definitive diagnosis in 50% of PH1 patients. The test offers a rapid turnaround time (15 days) with minimal risk to the patient. Demonstration of the expression of missense changes is essential to demonstrate pathogenicity.

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				E. D. Hopper, A. M. C. Pittman, M. C. Fitzgerald, and C. L. Tucker In Vivo and in Vitro Examination of Stability of Primary Hyperoxaluria-associated Human Alanine:Glyoxylate Aminotransferase J. Biol. Chem., November 7, 2008; 283(45): 30493 - 30502. [Abstract] [Full Text] [PDF]