AUA 2006 - ABST [1546] Role of mutations in the sodium dicarboxylate cotransporter-1 (NaDC1) in the etiology of hypocitraturia in calcium-oxalate stone disease

AUA 2006 - ABST [1546] Role of mutations in the sodium dicarboxylate cotransporter-1 (NaDC1) in the etiology of hypocitraturia in calcium-oxalate stone disease

Sven Lahme*, Volker Zimmermanns, Pforzheim, Germany; Arnulf Stenzl, Tuebingen, Germany; Eva Brauers, Aachen, Germany; Florain Lang, Tuebingen, Germany; Thomas Eggermann, Aachen, Germany.

Introduction and Objective: Etiology of urolithiasis is influenced by environmental as well as by genetic factors. Indeed, the genetic basis for specific metabolic disorders that lead to urolithiasis, such as cystinuria and oxaluria, is well established; however only little is known about the genetic basis of hypocitraturia as the major stone forming factors in calcium-oxalate stone disease. Urinary citrate concentration is primarily determined by its rate of reabsorption in the proximal tubule. Citrate reabsorption is mediated by NaDC1. Recent studies showed, that increased NaDC1 expression is associated with a decline in urinary citrate excretion. Aim of our study was to determine the role of mutations of the coding region of the NaDC1 as a cause for hypocitraturia.

Methods: Patient population was evaluated by means of 24h-urinary specimen and citrate load test. 13 patients with hypocitraturia less than 1 mmol/d were included in the study. Genomic DNA was extracted from peripheral lymphocytes by standard techniques. The coding sequence (12 exons) as well as the intron/exon boundaries of NaDC1 was screened by single strand conformation analysis (SSCP). Most exons were amplified as single fragments, but the larger exons (7 and 12) were split and amplified in several overlapping fragments to allow a reliable detection rate. PCR and SSCP were performed according to Eggermann et al., 1999. To demonstrate the sensitivity of our SSCP approach, 10 of the fragments were additionally analysed by denaturing high-performance liquid chromatography (DHPLC) according to Bergmann, 2004.

Results: By SSCP and DHPLC analysis, we detected unusual patterns in the fragments of exons 3, 8, and 12 of the NaDC1 coding sequence. Direct sequencing of these variations confirmed basepair substitutions which correspond to known SNPs (rs11568466 in exon 3, rs11568443 in intron 7, rs11568454 in exon12). All three variants were detected in patients as well as in controls.

Conclusions: In total, our results do not indicate a relevant role of mutations in NaDC1 in the etiology of hypocitraturia.
Wednesday, Wednesday, May 24, 2006 10:00 AM
Moderated Poster: Stone Disease: Research & New Technology (10:00 AM-12:00 PM)

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