BACKGROUND: Renal hypouricemia is a rare heterogeneous inherited disorder characterized by impaired tubular uric acid transport with severe complications, such as acute kidney injury and nephrolithiasis. Type 1 is caused by a loss-of-function mutation in the SLC22A12 gene (URAT1), while type 2 is caused by defects in the SLC2A9 gene (GLUT9). METHODS AND RESULTS: In this article we present clinical, biochemical and molecular genetics of two Czech patients. The serum uric acid in the probands was 57 and 98 µmol/l and expressed as an increase in the fractional excretion of uric acid (40 and 18 %). The sequencing analysis of SLC22A12 and SLC2A9 revealed novel variants p.R92C and p.R203C in URAT1 and p.G72D in GLUT9. Functional studies were performed for these novel variants and for previously reported variants p.I118HfsX27, p.G216R and p.N333S in GLUT9 responsible for renal hypouricemia in three probands from Czech Republic and United Kingdom. Functional studies showed significantly decreased urate uptake for all variants. However, urate uptake of GLUT9 variants prepared for both isoforms were not significantly different. CONCLUSIONS: This is the first complex function characterization of non-synonymous allelic variants in patients with renal hypouricemia regarding both GLUT9 isoforms. Our finding of defects in the SLC2A9 and SLC22A12 genes show the following: renal hypouricemia is not restricted to East Asia populations; urate uptake of GLUT9 variants prepared for both isoforms were not significantly different; renal hypouricemia type 2 has more wide clinical variability than type 1; the phenotypic severity of renal hypouricemia is not correlated with results of functional characterizations of URAT1 and GLUT9 variants.

• Klíčová slova
• GLUT9, Renal hypouricemia, SLC22A12, SLC2A9, URAT1, Uric acid transporters,
• MeSH
• dítě MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• močové kameny genetika   MeSH
• mutační analýza DNA MeSH
• přenašeče organických aniontů genetika   MeSH
• proteiny přenášející organické kationty genetika   MeSH
• proteiny usnadňující transport glukosy genetika   MeSH
• vrozené poruchy tubulárního transportu genetika   MeSH
• Xenopus MeSH
• zvířata MeSH
• Check Tag
• dítě MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladiství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• Názvy látek
• přenašeče organických aniontů MeSH
• proteiny přenášející organické kationty MeSH
• proteiny usnadňující transport glukosy MeSH
• SLC22A12 protein, human MeSH Prohlížeč
• SLC2A9 protein, human MeSH Prohlížeč

OBJECTIVE: Using European descent Czech populations, we performed a study of SLC2A9 and SLC22A12 genes previously identified as being associated with serum uric acid concentrations and gout. This is the first study of the impact of non-synonymous allelic variants on the function of GLUT9 except for patients suffering from renal hypouricemia type 2. METHODS: The cohort consisted of 250 individuals (150 controls, 54 nonspecific hyperuricemics and 46 primary gout and/or hyperuricemia subjects). We analyzed 13 exons of SLC2A9 (GLUT9 variant 1 and GLUT9 variant 2) and 10 exons of SLC22A12 by PCR amplification and sequenced directly. Allelic variants were prepared and their urate uptake and subcellular localization were studied by Xenopus oocytes expression system. The functional studies were analyzed using the non-parametric Wilcoxon and Kruskall-Wallis tests; the association study used the Fisher exact test and linear regression approach. RESULTS: We identified a total of 52 sequence variants (12 unpublished). Eight non-synonymous allelic variants were found only in SLC2A9: rs6820230, rs2276961, rs144196049, rs112404957, rs73225891, rs16890979, rs3733591 and rs2280205. None of these variants showed any significant difference in the expression of GLUT9 and in urate transport. In the association study, eight variants showed a possible association with hyperuricemia. However, seven of these were in introns and the one exon located variant, rs7932775, did not show a statistically significant association with serum uric acid concentration. CONCLUSION: Our results did not confirm any effect of SLC22A12 and SLC2A9 variants on serum uric acid concentration. Our complex approach using association analysis together with functional and immunohistochemical characterization of non-synonymous allelic variants did not show any influence on expression, subcellular localization and urate uptake of GLUT9.

• MeSH
• alely MeSH
• běloši MeSH
• biologický transport MeSH
• dna (nemoc) genetika   patologie   MeSH
• dospělí MeSH
• exprese genu MeSH
• frekvence genu MeSH
• hyperurikemie genetika   patologie   MeSH
• jednonukleotidový polymorfismus * MeSH
• lidé středního věku MeSH
• lidé MeSH
• přenašeče organických aniontů genetika   MeSH
• proteiny přenášející organické kationty genetika   MeSH
• proteiny usnadňující transport glukosy genetika   MeSH
• senioři MeSH
• studie případů a kontrol MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Česká republika MeSH
• Názvy látek
• přenašeče organických aniontů MeSH
• proteiny přenášející organické kationty MeSH
• proteiny usnadňující transport glukosy MeSH
• SLC22A12 protein, human MeSH Prohlížeč
• SLC2A9 protein, human MeSH Prohlížeč