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

2007 ◽  
Vol 53 (7) ◽  
pp. 1216-1221 ◽  
Author(s):  
Emma Williams ◽  
Gill Rumsby
Keyword(s):  
Molecular Diagnosis ◽  
Primary Hyperoxaluria ◽  
Definitive Diagnosis ◽  
Minimal Risk ◽  
Primary Hyperoxaluria Type 1 ◽  
Primary Hyperoxaluria Type ◽  
Agxt Gene ◽  
Hyperoxaluria Type

Abstract 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.

scholarly journals ATP-dependent degradation of a mutant serine: pyruvate/alanine:glyoxylate aminotransferase in a primary hyperoxaluria type 1 case.

1993 ◽  
Vol 123 (5) ◽  
pp. 1237-1248 ◽  
Author(s):  
K Nishiyama ◽  
T Funai ◽  
S Yokota ◽  
A Ichiyama
Keyword(s):  
Primary Hyperoxaluria ◽  
Normal Liver ◽  
Single Amino Acid ◽  
Coding Region ◽  
Primary Hyperoxaluria Type 1 ◽  
Primary Hyperoxaluria Type ◽  
Alanine:Glyoxylate Aminotransferase ◽  
Hyperoxaluria Type

Primary hyperoxaluria type 1 (PH 1), an inborn error of glyoxylate metabolism characterized by excessive synthesis of oxalate and glycolate, is caused by a defect in serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT). This enzyme is peroxisomal in human liver. Recently, we cloned SPT/AGT-cDNA from a PH 1 case, and demonstrated a point mutation of T to C in the coding region of the SPT/AGT gene encoding a Ser to Pro substitution at residue 205 (Nishiyama, K., T. Funai, R. Katafuchi, F. Hattori, K. Onoyama, and A. Ichiyama. 1991. Biochem. Biophys. Res. Commun. 176:1093-1099). In the liver of this patient, SPT/AGT was very low with respect to not only activity but also protein detectable on Western blot and immunoprecipitation analyses. Immunocytochemically detectable SPT/AGT labeling was also low, although it was detected predominantly in peroxisomes. On the other hand, the level of translatable SPT/AGT-mRNA was higher than normal, indicating that SPT/AGT had been synthesized in the patient's liver at least as effectively as in normal liver. Rapid degradation of the mutant SPT/AGT was then demonstrated in transfected COS cells and transformed Escherichia coli, accounting for the low level of immunodetectable mutant SPT/AGT in the patient's liver. The mutant SPT/AGT was also degraded much faster than normal in an in vitro system with a rabbit reticulocyte extract, and the degradation in vitro was ATP dependent. These results indicate that a single amino acid substitution in SPT/AGT found in the PH1 case leads to a reduced half-life of this protein. It appears that the mutant SPT/AGT is recognized in cells as an abnormal protein to be eliminated by degradation.

AGXT Gene Mutations and Prevalence of Primary Hyperoxaluria Type 1 in Moroccan Population

2015 ◽  
Vol 19 (11) ◽  
pp. 623-628 ◽  
Author(s):  
Lamiae Boualla ◽  
Mariam Tajir ◽  
Najat Oulahiane ◽  
Jaber Lyahyai ◽  
Fatima Zahra Laarabi ◽  
...  
Keyword(s):  
Gene Mutations ◽  
Primary Hyperoxaluria ◽  
Primary Hyperoxaluria Type 1 ◽  
Moroccan Population ◽  
Primary Hyperoxaluria Type ◽  
Agxt Gene ◽  
Hyperoxaluria Type

scholarly journals Molecular analysis of the AGXT gene in Syrian patients suspected with primary hyperoxaluria type 1

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Hossam Murad ◽  
Mohamad Baseel Alhalabi ◽  
Amir Dabboul ◽  
Nour Alfakseh ◽  
Mohamad Sayah Nweder ◽  
...  
Keyword(s):  
Dna Sequencing ◽  
Gene Mutations ◽  
Primary Hyperoxaluria ◽  
Detection Methods ◽  
Primary Hyperoxaluria Type 1 ◽  
Direct Dna Sequencing ◽  
Primary Hyperoxaluria Type ◽  
Agxt Gene ◽  
Hyperoxaluria Type

Abstract Background Characterization of the molecular basis of primary hyperoxaluria type 1 (PH-1) in Syria has been accomplished through the analysis of 90 unrelated chromosomes from 45 Syrians patients with PH-1 from different regions. Methods Alanine glyoxylate aminotransferase (AGXT) gene mutations have been analyzed by using molecular detection methods based on the direct DNA sequencing for all exons of the AGXT gene. Results Seventeen pathogenic mutations were detected in our patients. Six mutations were novels. The three most frequent mutations were c.33_34insC (p.Lys12fs) in Exon 1, c.584 T < G; p.Met195Arg in exon 5 and c.1007 T > A (p.Val336Asp) in exon 10, with a frequency of 33.3%, 12.2%, and 11.1%, respectively. Conclusion DNA sequencing used in this study can offer a useful method to investigate the mutations in Syrian PH-1 patients, and could offer an accurate tool for prenatal diagnosis and genetic counseling.

scholarly journals Inhibition of alanine:glyoxylate aminotransferase 1 dimerization is a prerequisite for its peroxisome-to-mitochondrion mistargeting in primary hyperoxaluria type 1.

1996 ◽  
Vol 135 (4) ◽  
pp. 939-951 ◽  
Author(s):  
J M Leiper ◽  
P B Oatey ◽  
C J Danpure
Keyword(s):  
Primary Hyperoxaluria ◽  
Mitochondrial Import ◽  
Primary Hyperoxaluria Type 1 ◽  
Whole Cells ◽  
Primary Hyperoxaluria Type ◽  
Alanine:Glyoxylate Aminotransferase ◽  
Hyperoxaluria Type

Peroxisome-to-mitochondrion mistargeting of the homodimeric enzyme alanine:glyoxylate aminotransferase 1 (AGT) in the autosomal recessive disease primary hyperoxaluria type 1 (PH1) is associated with the combined presence of a normally occurring Pro(11)Leu polymorphism and a PH1-specific Gly170Arg mutation. The former leads to the formation of a novel NH2-terminal mitochondrial targeting sequence (MTS), which although sufficient to direct the import of in vitro-translated AGT into isolated mitochondria, requires the additional presence of the Gly170Arg mutation to function efficiently in whole cells. The role of this mutation in the mistargeting phenomenon has remained elusive. It does not interfere with the peroxisomal targeting or import of AGT. In the present study, we have investigated the role of the Gly170Arg mutation in AGT mistargeting. In addition, our studies have led us to examine the relationship between the oligomeric status of AGT and the peroxisomal and mitochondrial import processes. The results obtained show that in vitro-translated AGT rapidly forms dimers that do not readily exchange subunits. Although the presence of the Pro(11)Leu or Gly170Arg substitutions alone had no effect on dimerization, their combined presence abolished homodimerization in vitro. However, AGT containing both substitutions was still able to form heterodimers in vitro with either normal AGT or AGT containing either substitution alone. Expression of various combinations of normal and mutant, as well as epitope-tagged and untagged forms of AGT in whole cells showed that normal AGT rapidly dimerizes in the cytosol and is imported into peroxisomes as a dimer. This dimerization prevents mitochondrial import, even when the AGT possesses an MTS generated by the Pro(11)Leu substitution. The additional presence of the Gly170Arg substitution impairs dimerization sufficiently to allow mitochondrial import. Pharmacological inhibition of mitochondrial import allows AGT containing both substitutions to be imported into peroxisomes efficiently, showing that AGT dimerization is not a prerequisite for peroxisomal import.

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