rs12917707 — UMOD

UMOD — The Strongest Genetic Signal for Kidney Disease Risk

The UMOD gene encodes uromodulin¹¹ uromodulin
Also known as Tamm-Horsfall protein, the most abundant protein in normal human urine, produced exclusively by cells of the thick ascending limb of the loop of Henle, a glycoprotein that plays central roles in kidney tubular function, salt handling, innate immunity, and protection against urinary tract infections. The rs12917707 variant sits in the promoter region²² promoter region
Located approximately 2 kb upstream of the UMOD transcription start site on chromosome 16p12 of this gene, where it controls how much uromodulin your kidneys produce. This single variant is the strongest common-variant GWAS signal³³ strongest common-variant GWAS signal
Identified in the CKDGen consortium meta-analysis as having the largest effect size among all eGFR-associated loci for chronic kidney disease risk ever discovered.

The Mechanism

The G allele (risk, major) drives higher transcription of UMOD⁴⁴ higher transcription of UMOD
Risk allele homozygotes show approximately 2-fold higher UMOD mRNA in kidney tissue compared to protective allele homozygotes, resulting in elevated urinary uromodulin concentrations. While uromodulin has protective functions (anti-bacterial defense, prevention of kidney stones), excess production creates a paradoxical problem: uromodulin activates the NKCC2 sodium cotransporter⁵⁵ NKCC2 sodium cotransporter
Na-K-2Cl cotransporter in the thick ascending limb of the loop of Henle, the primary site of sodium reabsorption in the kidney in the kidney's loop of Henle, promoting excessive sodium reabsorption. This leads to salt-sensitive hypertension and, over time, kidney damage. The protective T allele produces less uromodulin, resulting in more appropriate sodium excretion and lower blood pressure.

Mendelian randomization studies have confirmed this is a causal relationship⁶⁶ a causal relationship
Each SD increase in genetically predicted urinary uromodulin decreases eGFR by 0.15 SD and increases CKD odds — uromodulin directly impairs kidney function independent of blood pressure, though the blood pressure effect compounds the damage. The effect is strongly age-dependent⁷⁷ age-dependent
Little or no effect on serum creatinine before age 50, with increasing effect thereafter (interaction P=3.0e-17), meaning the risk accumulates as the kidney ages and becomes less resilient.

The Evidence

The original CKDGen consortium GWAS⁸⁸ CKDGen consortium GWAS
Kottgen et al. 2009, 19,877 discovery + 21,466 replication participants across multiple European cohorts identified rs12917707 as genome-wide significant for both eGFR and CKD. Each copy of the protective T allele was associated with approximately 20% reduced CKD risk. A large Icelandic study⁹⁹ large Icelandic study
Gudbjartsson et al. 2010, 3,203 CKD cases and 38,782 controls plus kidney stone analysis using the perfectly linked rs4293393 confirmed the CKD association (OR 1.25, 95% CI 1.17-1.35, P=4.1x10^-10) and revealed a dual effect: while the risk allele increases CKD susceptibility, it simultaneously protects against kidney stones (OR 0.88, P=5.7x10^-5) — likely because higher uromodulin inhibits calcium crystal aggregation.

The mechanistic breakthrough¹⁰¹⁰ mechanistic breakthrough
Trudu et al. Nature Medicine 2013 — transgenic mice overexpressing uromodulin developed salt-sensitive hypertension and age-dependent renal lesions came when Trudu et al. demonstrated that UMOD risk variants increase uromodulin expression in both cell culture and human kidney tissue, and that transgenic mice overexpressing uromodulin developed salt-sensitive hypertension and kidney lesions mimicking human aging kidneys. A meta-analysis of urinary uromodulin¹¹¹¹ meta-analysis of urinary uromodulin
Olden et al. JASN 2014, 10,884 individuals across six European cohorts quantified the dose-dependent effect: geometric mean urinary uromodulin levels were 10.24, 14.05, and 17.67 mcg/g creatinine for TT, GT, and GG carriers respectively.

Practical Implications

The pharmacogenomic implications are particularly actionable. Because the risk allele drives hypertension through NKCC2 activation in the loop of Henle, loop diuretics¹²¹² loop diuretics
Furosemide, torasemide, bumetanide — drugs that block NKCC2 specifically are mechanistically matched to this genotype. A genotype-blinded clinical trial¹³¹³ genotype-blinded clinical trial
McCallum et al. Hypertension 2024, 174 evaluable hypertensive participants receiving torasemide for 16 weeks confirmed that GG homozygotes (at the linked rs13333226) achieved 3.35 mmHg greater systolic blood pressure reduction with torasemide compared to carriers of the protective allele. This represents one of the clearest examples of pharmacogenomic-guided antihypertensive therapy.

Salt restriction is especially relevant for risk allele carriers, since the hypertensive effect is specifically salt-sensitive. The age-dependent nature of the risk also means that monitoring kidney function (eGFR) becomes increasingly important after age 50, when the variant's effect on serum creatinine becomes pronounced.

Interactions

The rs12917707 variant is in perfect linkage disequilibrium (r²=1.0) with rs4293393 and strong LD with rs13333226. These three SNPs tag the same functional haplotype in the UMOD promoter. The UMOD locus interacts with age as a modifier — the CKD risk effect is minimal before 50 and increases substantially thereafter, particularly in the context of comorbid hypertension or diabetes. The variant also has a paradoxical relationship with kidney stone risk: the same allele that increases CKD risk protects against calcium stones, creating a clinical scenario where interventions must balance both outcomes.