Gene locus ambiguity in posterior urethral valves/prune-belly syndrome

Lower urinary tract obstruction by posterior urethral valves (PUV) is an important cause of congenital renal failure in male infants. Though population-based studies point to a role of genetic factors in the etiology of PUV, no clear evidence for a specific gene defect for PUV has been observed so far. Here we present a consanguineous family with four male descendants affected by PUV and a healthy girl, suggestive of autosomal recessive inheritance. One boy presented with prune-belly syndrome (PBS) in addition to PUV. Using a DNA chip-based genome-wide linkage analysis, we identified a region of homozygosity for the affected boys in an interval of 35 cM on chromosome 1q41-44 with a maximum multipoint LOD score of Z(max) = 3.134 at theta = 0 for single nucleotide polymorphisms (SNPs) rs158724-rs720163. By applying a second genetic model based on the assumption of a male-limited phenotype and the girl being carrier of the genetic defect without expressing the phenotype, a second alternative locus of 9 cM on chromosome 11p11 was identified with a LOD score of Z(max) = 3.61 at theta = 0. Equal significance for both loci with a LOD score of Z(max) = 3.01 at theta = 0 was obtained after the affection status of the female descendant was set "unknown". We suppose that most probably, only one of the two identified loci harbours the disease-causing gene. As the interpretation of the girl's status remains uncertain, we are not able to exclude one of the two loci. Analyses of additional informative families will be important to exclude one of the two loci and to restrict the critical interval.