Insertion/Deletion Polymorphisms in the ΔNp63 Promoter Are a Risk Factor for Bladder Exstrophy Epispadias Complex

Abstract

Bladder exstrophy epispadias complex (BEEC) is a severe congenital anomaly; however, the genetic and molecular mechanisms underlying the formation of BEEC remain unclear. TP63, a member of TP53 tumor suppressor gene family, is expressed in bladder urothelium and skin over the external genitalia during mammalian development. It plays a role in bladder development. We have previously shown that p63−/− mouse embryos developed a bladder exstrophy phenotype identical to human BEEC. We hypothesised that TP63 is involved in human BEEC pathogenesis. RNA was extracted from BEEC foreskin specimens and, as in mice, ΔNp63 was the predominant p63 isoform. ΔNp63 expression in the foreskin and bladder epithelium of BEEC patients was reduced. DNA was sequenced from 163 BEEC patients and 285 ethnicity-matched controls. No exon mutations were detected. Sequencing of the ΔNp63 promoter showed 7 single nucleotide polymorphisms and 4 insertion/deletion (indel) polymorphisms. Indel polymorphisms were associated with an increased risk of BEEC. Significantly the sites of indel polymorphisms differed between Caucasian and non-Caucasian populations. A 12-base-pair deletion was associated with an increased risk with only Caucasian patients (p = 0.0052 Odds Ratio (OR) = 18.33), whereas a 4-base-pair insertion was only associated with non-Caucasian patients (p = 0.0259 OR = 4.583). We found a consistent and statistically significant reduction in transcriptional efficiencies of the promoter sequences containing indel polymorphisms in luciferase assays. These findings suggest that indel polymorphisms of the ΔNp63 promoter lead to a reduction in p63 expression, which could lead to BEEC.

Candidate gene association study implicates p63 in the etiology of nonsyndromic bladder‐exstrophy‐epispadias complex

“…Furthermore, a genome‐wide expression analysis independently implicated p63 as a contributing factor in the BEEC etiology (Qi et al, ). A recent study (Wilkins et al, ) independently corroborated our data (Ching et al, ) and also suggests that ΔNp63 is the dominant promoter in human tissue and its expression is significantly reduced in BEEC tissue in early bladder formation. The authors also showed that two insertion–deletion polymorphisms including a 12‐base‐pair deletion (rs6148242) and a homozygous 1bp insertion polymorphism (rs5855273) in the ΔNp63 promoter were associated with a highly increased risk for the development of nonsyndromic BEEC among Caucasians.…”

“…Recently, Wilkins et al, () reported two polymorphisms in the ΔNp63 promoter (rs6148242, rs5855273) to be strongly associated with an increased risk of BEEC among Caucasian patients. Although we found several SNPs in the p63 gene that showed altered transmission from the parents to their BEEC offspring, the results lost statistical significance after correction for multiple testing.…”

Is 1p36 deletion associated with anterior body wall defects?

“…Advanced parental age is also considered as a risk factor for the complex [Boyadjiev et al, 2004]. Insertion/deletion polymorphisms related to DNp63 gene have also been reported as a genetic risk factor for BEEC [Wilkins et al, 2012]. Apart from sporadic cases, CBE is listed in association with 14 entities in the London Dysmorphology Database (LMD).…”

Clinical and risk factor analysis of cloacal defects in the National Birth Defects Prevention Study

“…An unpublished whole exome sequencing study in six CE child‐parent trios performed through the Center for Mendelian Genomics at the University of Washington did not reveal any plausible candidate genes (Keegan et al, unpublished). Additionally, the few candidate gene and genome‐wide association studies performed to date on the bladder exstrophy‐epispadias complex (BEEC)—which includes BE, PC, and CE—reported several potential candidate genes, including ISL1 (Draaken et al, ), p63 (Qi et al, ; Wilkins et al, ), and WNT3 (Reutter et al, ).…”