Another case of autosomal dominant exstrophy of the bladder

Exome sequencing of child-parent trios with bladder exstrophy: Findings in 26 children

Bladder exstrophy (BE) is a rare, lower ventral midline defect with the bladder and part of the urethra exposed. The etiology of BE is unknown but thought to be influenced by genetic variation with more recent studies suggesting a role for rare variants. As such, we conducted paired-end exome sequencing in 26 child/mother/father trios. Three children had rare (allele frequency ≤ 0.0001 in several public databases) inherited variants in TSPAN4, one with a loss-of-function variant and two with missense variants. Two children had loss-of-function variants in TUBE1. Four children had rare missense or nonsense variants (one per child) in WNT3, CRKL, MYH9, or LZTR1, genes previously associated with BE. We detected 17 de novo missense variants in 13 children and three de novo loss-of-function variants (AKR1C2, PRRX1, PPM1D) in three children (one per child). We also detected rare compound heterozygous loss-of-function variants in PLCH2 and CLEC4M and rare inherited missense or loss-of-function variants in additional genes applying autosomal recessive (three genes) and X-linked recessive inheritance models (13 genes). Variants in two genes identified may implicate disruption in cell migration (TUBE1) and adhesion (TSPAN4) processes, mechanisms proposed for BE, and provide additional evidence for rare variants in the development of this defect.

Early Diagnosis of Bladder Exstrophy: Quantitative Assessment of a Low-Inserted Umbilical Cord

OBJECTIVES

Bladder exstrophy is a rare severe congenital malformation. Early prenatal diagnosis is scarcely described in the literature. Low insertion of the umbilical cord is a constant anatomic feature of bladder exstrophy. The aim of our study was to assess whether early measurements of the umbilical cord insertion-to-genital tubercle length may serve as quantitative measurements for a low-inserted umbilical cord in cases of bladder exstrophy.

METHODS

The umbilical cord insertion-to-genital tubercle length was prospectively measured in all cases referred for a nonvisualized urinary bladder before 18 weeks' gestation. Final diagnoses were compared with prenatal measurements.

RESULTS

Fifteen fetuses were evaluated for a nonvisualized bladder at a mean gestational age of 15.7 weeks (range, 14-17 weeks). Of them, 6 cases were diagnosed with bladder exstrophy, and 9 cases had a normal urinary bladder. All cases with bladder exstrophy had an umbilical cord insertion-to-genital tubercle length below the fifth percentile for gestational age, whereas cases with a normal bladder had a normal measurement.

CONCLUSIONS

Fetuses with bladder exstrophy have an umbilical cord insertion-to-genital tubercle length below the fifth percentile of the general population. This measurement may serve as a complementary objective sonographic parameter in the prenatal assessment and counseling of cases suspected of having bladder exstrophy during early pregnancy.

[Ultrasound of the fetal urinary system during the first trimester of pregnancy]

The detection of abnormalities of the fetal urinary system in the first trimester of pregnancy is constantly improving, namely owing to the improved resolution of the image, the use of the endovaginal approach and thanks to sonographers' constant training. The pathological aspects, usually detected in the second trimester of pregnancy, can be suspected early in the first trimester and range from kidneys' cavity dilation to bilateral renal agenesis, polycystic kidney disease, multi-cystic dysplasia and bladder megavessia or bladder exstrophy. A poly-malformative syndrome is to be found out. The detection of an abnormality of the urinary tract requires a close ultrasound check. Very often, the pathological aspects tend to disappear spontaneously. In particular, the non-visualization of the bladder requires repeated examinations during the same session or even a little later in the pregnancy. We will carry out a review of the literature by pointing out the usual and unusual aspects of the fetal urinary system visible in the first trimester and we will as well propose an algorithm describing how to deal with abnormalities of the urinary tract that can be found out at first trimester ultrasound.

Insertion/deletion polymorphisms in the ΔNp63 promoter are a risk factor for bladder exstrophy epispadias complex

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.

Bladder exstrophy epispadias complex is a severe congenital abnormality. The affected babies' bladders are born open, leaking urine constantly. Treatment involves multiple major reconstructive surgeries and the need for lifelong care for the complications of the disease. Although a number of studies have suggested a genetic cause of the disease, the genetic and molecular mechanism underlying the formation of BEEC remains unknown. One gene, TP63, plays a crucial role in the early bladder development. Two different genetic promoters of TP63 produce different forms of the protein with opposing properties. We have shown mice lacking p63 displayed a deformity complex identical to human BEEC. There are no genetic mutations in the p63 protein in BEEC, so genetic variants in the promoter could alter protein expression. Our hypothesis was that loss of p63 expression due to sequence polymorphisms in a promoter is a risk factor for BEEC. We found promoter sequence variants that were statistically associated with the disease and the sequence variant location varied between Caucasian and non-Caucasian patients. This is particularly important as Caucasian populations have a higher risk of BEEC. These findings provide an explanation of BECC and a base for further study of TP63 related genes in this disease.

Bladder exstrophy and epispadias complex in sibling: case report and review of literature

The bladder exstrophy and classic epispadias represent a spectrum of congenital anomalies with different degrees of anterior midline defect. Although the anomaly usually occurs sporadically there are some cases indicative of a strong genetic component. We present the clinical data of two siblings with bladder exstrophy and epispadias complex (BEEC), who were the product of consanguineous union. All previous reports of familial BEEC in the literature have been reviewed.

Genetische und molekularbiologische Aspekte des Blasenekstrophie-Epispadie-Komplexes (BEEK)

The bladder exstrophy and epispadias complex (BEEC) is an anterior midline defect with variable expression involving the infraumbilical abdominal wall including the pelvis, urinary tract, and external genitalia. The incidence varies with regard to ethnical background, sex, and phenotypic expression, and an incidence of 1:20,000 to 1:80,000 has been observed in the middle European population. No gene defect has been attributed to BEEC thus far and chromosomal aberrations or genetic syndromes associated with BEEC have only rarely been reported. According to epidemiological data, a complex genetic as well as a multifactorial mode of inheritance could underlie BEEC. However, no single teratogenic agent or environmental factor has been identified, which could play a dominant role in the expression of the BEEC.A risk of recurrence of 0.5-3% has been described in families with one affected subject. These values correspond to an increased recurrence risk estimated to be as high as 200- to 800-fold when compared to the common population. Due to the paucity of affected sib pairs and suitable multiplex families, conventional linkage analysis to identify candidate genes causally related with BEEC appears to be unfeasible. Large association studies and consecutive linkage disequilibrium mapping should therefore lead to the identification of candidate genes. Also new methods including matrix-based comparative genomic hybridization (CGH) are promising and have successfully been used in the past (e.g., CHARGE association). Moreover, the low incidence of the BEEC requires close cooperation between clinicians in the operative and nonoperative specialties as well as geneticists for successful gene search.