Late diagnosis of primary hyperoxaluria type 2 in the adult: Effect of a novel mutation in GRHPR gene on enzymatic activity and molecular modeling

N Levin-Iaina, D Dinour, L Romero, R Ron, RL Brady, SD Cramer, EJ Holtzman

Research output: Contribution to journalArticle (Academic Journal)peer-review

11 Citations (Scopus)

Abstract

Purpose Genetic causes of nephrolithiasis are underestimated. Primary hyperoxaluria type 2 is a rare autosomal recessive disease caused by mutations in the GRHPR gene, leading to an accumulation of oxalate and L-glycerate with recurrent kidney stone formation and nephrocalcinosis, and the later development of renal failure and systemic oxalate depositions. We studied the effects of a novel GRHPR mutation on GRHPR enzymatic activity and molecular modeling. Materials and Methods Genomic DNA from a 50-year-old male with a late diagnosis of primary hyperoxaluria type 2 was extracted, analyzed and compared with the established human GRHPR gene sequence. Restriction enzyme analysis of the patient, 30 healthy controls and 30 patients with nephrolithiasis of various causes was done to confirm the presence of the mutation. GRHPR activity was analyzed by site directed mutagenesis of WT and mutant clones. We studied the effects of the mutation on enzymatic molecular modeling. Results We found the novel homozygous single missense mutation A975G in exon 9, creating an amino acid change from asparagine to aspartic acid in position 312. No mutations were detected in restriction enzyme analysis in all 30 healthy controls and 30 patients with nephrolithiasis of various causes. Transfected cells with the mutant clone showed abolished GRHPR activity. Molecular modeling studies revealed that the mutation was likely to disrupt the correct folding of the GRHPR substrate binding domain, hence affecting the enzyme active site. Conclusions Primary hyperoxaluria type 2 should be considered in patients at adult stone clinics who have had a history of nephrolithiasis since childhood, especially in those with consanguineous parents. Biochemical analysis followed by mutation identification should be the approach for making the definitive diagnosis of primary hyperoxaluria type 2. Key Words: kidney; nephrolithiasis; glyoxylate reductase; hyperoxaluria; primary; mutation Abbreviations: AGT, alanine:glyoxylate aminotransferase; GRHPR, glyoxylate reductase hydroxypyruvate reductase; PCR, polymerase chain reaction; PH, primary hyperoxaluria; PH1, PH type 1; PH2, PH type 2
Translated title of the contributionLate diagnosis of primary hyperoxaluria type 2 in the adult: Effect of a novel mutation in GRHPR gene on enzymatic activity and molecular modeling
Original languageEnglish
Pages (from-to)2146 - 2151
Number of pages6
JournalJournal of Urology
Volume181 (5)
DOIs
Publication statusPublished - May 2009

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