A genome search for primary vesicoureteral reflux shows further evidence for genetic heterogeneity

Abstract

Vesicoureteral reflux (VUR) is the most common disease of the urinary tract in children. In order to identify gene(s) involved in this complex disorder, we performed a genome-wide search in a selected sample of 31 patients with primary VUR from eight families originating from southern Italy. Sixteen additional families with 41 patients were included in a second stage. Nonparametric, affected-only linkage analysis identified four genomic areas on chromosomes 1, 3, and 4 (p < 0.05); the best result corresponded to the D3S3681-D3S1569 interval on chromosome 3 (nonparametric linkage score, NPL = 2.75, p = 0.008). This region was then saturated with 26 additional markers, tested in the complete group of 72 patients from 24 families (NPL = 2.01, p = 0.01). We identified a genomic area on 3q22.2-23, where 26 patients from six multiplex families shared overlapping haplotypes. However, we did not find evidence for a common ancestral haplotype. The region on chromosome 1 was delimited to 1p36.2-34.3 (D1S228-D1S255, max. NPL = 1.70, p = 0.03), after additional fine typing. Furthermore, on chromosome 22q11.22-12.3, patients from a single family showed excess allele sharing (NPL = 3.35, p = 0.015). Only the chromosome 3q region has been previously reported in the single genome-wide screening available for primary VUR. Our results suggest the presence of several novel loci for primary VUR, giving further evidence for the genetic heterogeneity of this disorder.

Fig. 1

Selection and distribution of families and patients included in the study. VUR vesicoureteral reflux

Fig. 2

A selection of pedigrees enrolled in the study is shown. Squares indicate males and circles indicate females. Family members with unknown phenotype are in grey, whereas those unaffected (normal voiding cystourethrography or direct radionuclide cystography before age of 5 years and unrelated spouses) are in white. An asterisk highlights the individuals genotyped in the study. A number following the asterisk indicates the patients/obligate carriers reported in Fig. 3. Individuals with urinary tract infections by history and “obligate carriers” are considered as unknown in all analyses. a Nine multiplex pedigrees included in the genome-wide scan are shown. An additional five parent–child trios are not displayed. Family 6 was excluded from the linkage analysis due to the bilineal inheritance. b All 11 multiplex pedigrees included in the fine-typing stage are shown. VUR vesicoureteral reflux, RN reflux nephropathy, ESRF end-stage renal failure, UTIs urinary tract infections

Fig. 2

A selection of pedigrees enrolled in the study is shown. Squares indicate males and circles indicate females. Family members with unknown phenotype are in grey, whereas those unaffected (normal voiding cystourethrography or direct radionuclide cystography before age of 5 years and unrelated spouses) are in white. An asterisk highlights the individuals genotyped in the study. A number following the asterisk indicates the patients/obligate carriers reported in Fig. 3. Individuals with urinary tract infections by history and “obligate carriers” are considered as unknown in all analyses. a Nine multiplex pedigrees included in the genome-wide scan are shown. An additional five parent–child trios are not displayed. Family 6 was excluded from the linkage analysis due to the bilineal inheritance. b All 11 multiplex pedigrees included in the fine-typing stage are shown. VUR vesicoureteral reflux, RN reflux nephropathy, ESRF end-stage renal failure, UTIs urinary tract infections

Fig. 3

Haplotype analysis in families supporting the chromosome 3 region after fine typing. A selection of microsatellite markers is shown. The shared genomic region is shown in grey; recombinants are shown in white blocks