A novel SNP in the 5' regulatory region of organic anion transporter 1 is associated with chronic kidney disease

We aimed to analyze the associations of single nucleotide polymorphisms (SNP) in the 5' regulatory region of the human organic anion transporter 1 (OAT1) gene with chronic kidney disease (CKD). A case-control study including age- and sex-matched groups of normal subjects and patients with CKD (n = 162 each) was designed. Direct sequencing of the 5' regulatory region (+88 to -1196 region) showed that patients with CKD had a higher frequency of the -475 SNP (T > T/G) than normal subjects (14/162 vs. 2/162). The luciferase activity assay results indicated that the -475G SNP had a higher promoter efficiency than the -475T SNP. Chromatin immunoprecipitation (ChIP) and LC/MS/MS analyses showed that the -475G SNP up-regulated 26 proteins and down-regulated 74 proteins. The Southwestern blot assay results revealed that the -475G SNP decreased the binding of Hepatoma-derived growth factor (HDGF), a transcription repressor, compared to the -475T SNP. Overexpression of HDGF significantly down-regulated OAT1 in renal tubular cells. Moreover, a zebrafish animal model showed that HDGF-knockdown zebrafish embryos had higher rates of kidney malformation than wild-type controls [18/78 (23.1%) vs. 1/30 (3.3%)]. In conclusion, our results suggest that an OAT1 SNP might be clinically associated with CKD. Renal tubular cells with the -475 SNP had increased OAT1 expression, which resulted in increased transportation of organic anion toxins into cells. Cellular accumulation of organic anion toxins caused cytotoxicity and resulted in CKD.