Significance Statement Vesicoureteral reflux (VUR) is associated with progressive kidney disease. Familial aggregation supports a hereditary basis; however, its genetic architecture remains to be elucidated. The largest VUR copy number variant analysis and genome-wide association study to date accounts for multiple modes of inheritance and sex-specific effects in VUR, identifying three study-wide significant and five suggestive loci with large effects, containing canonical developmental genes including WDPCP and WNT5A . Results of experiments in mice support novel roles of Wnt5a in urogenital development. Altogether, 6% of patients carried high-risk genotypes. These findings have important implications for VUR screening. Background Vesicoureteral reflux (VUR) is a common, familial genitourinary disorder, and a major cause of pediatric urinary tract infection (UTI) and kidney failure. The genetic basis of VUR is not well understood. Methods A diagnostic analysis sought rare, pathogenic copy number variant (CNV) disorders among 1737 patients with VUR. A GWAS was performed in 1395 patients and 5366 controls, of European ancestry. Results Altogether, 3% of VUR patients harbored an undiagnosed rare CNV disorder, such as the 1q21.1, 16p11.2, 22q11.21, and triple X syndromes ((OR, 3.12; 95% CI, 2.10 to 4.54; P =6.35×10 −8 ) The GWAS identified three study-wide significant and five suggestive loci with large effects (ORs, 1.41–6.9), containing canonical developmental genes expressed in the developing urinary tract ( WDPCP, OTX1, BMP5, VANGL1, and WNT5A ). In particular, 3.3% of VUR patients were homozygous for an intronic variant in WDPCP (rs13013890; OR, 3.65; 95% CI, 2.39 to 5.56; P =1.86×10 –9 ). This locus was associated with multiple genitourinary phenotypes in the UK Biobank and eMERGE studies. Analysis of Wnt5a mutant mice confirmed the role of Wnt5a signaling in bladder and ureteric morphogenesis. Conclusions These data demonstrate the genetic heterogeneity of VUR. Altogether, 6% of patients with VUR harbored a rare CNV or a common variant genotype conferring an OR >3. Identification of these genetic risk factors has multiple implications for clinical care and for analysis of outcomes in VUR.
Urinary tract development depends on a complex series of events in which the ureter moves from its initial branch point on the nephric duct (ND) to its final insertion site in the cloaca (the primitive bladder and urethra). Defects in this maturation process can result in malpositioned ureters and hydronephrosis, a common cause of renal disease in children. Here, we report that insertion of the ND into the cloaca is an unrecognized but crucial step that is required for proper positioning of the ureter and that depends on Ret signaling. Analysis of Ret mutant mice at birth reveals hydronephrosis and defective ureter maturation, abnormalities that our results suggest are caused, at least in part, by delayed insertion of the ND. We find a similar set of malformations in mutants lacking either Gata3 or Raldh2. We show that these factors act in parallel to regulate ND insertion via Ret. Morphological analysis of ND extension in wild-type embryos reveals elaborate cellular protrusions at ND tips that are not detected in Ret, Gata3 or Raldh2 mutant embryos, suggesting that these protrusions may normally be important for fusion with the cloaca. Together, our studies reveal a novel Ret-dependent event, ND insertion, that, when abnormal, can cause obstruction and hydronephrosis at birth; whether ND defects underlie similar types of urinary tract abnormalities in humans is an interesting possibility.
