Candidate gene association study implicatesp63in the etiology of nonsyndromic bladder-exstrophy-epispadias complex

Rare exonic CELSR3 variants identified in Bladder Exstrophy Epispadias Complex

Introduction/background

Bladder exstrophy epispadias complex (BEEC) is a rare congenital anomaly of unknown etiology, although, genetic and environmental factors have been associated with its development. Variants in several genes expressed in the urogenital pathway have been reported as causative for bladder exstrophy in human and murine models. The expansion of next-generation sequencing and molecular genomics has improved our ability to identify the underlying genetic causes of similarly complex diseases and could thus assist with the investigation of the molecular basis of BEEC.

Objective

The objective was to identify the presence of rare heterozygous variants in genes previously implicated in bladder exstrophy and correlate them with the presence or absence of bladder regeneration in our study population.

Patients and Methods

We present a case series of 12 patients with BEEC who had bladder biopsies performed by pediatric urology during bladder neck reconstruction or bladder augmentation. Cases were classified as "sufficient" or "insufficient" (n = 5 and 7, respectively) based on a bladder volume of greater than or less than 40% of expected bladder size. Control bladder tissue specimens were obtained from patients (n = 6) undergoing biopsies for conditions other than bladder exstrophy. Whole exome sequencing was performed on DNA isolated from the bladder specimens. Based on the hypothesis of de novo mutations, as well as the potential implications of autosomal dominant conditions with incomplete penetrance, each case was evaluated for autosomal dominant variants in a set of genes previously implicated in BEEC.

Results

Our review of the literature identified 44 genes that have been implicated in human models of bladder exstrophy. Our whole exome sequencing data analysis identified rare variants in two of these genes among the cases classified as sufficient, and seven variants in five of these genes among the cases classified as insufficient.

Conclusion

We identified rare variants in seven previously implicated genes in our BEEC specimens. Additional research is needed to further understand the cellular signaling underlying this potentially genetically heterogeneous embryological condition.

The Genomic Architecture of Bladder Exstrophy Epispadias Complex

The bladder exstrophy-epispadias complex (BEEC) is an abdominal midline malformation comprising a spectrum of congenital genitourinary abnormalities of the abdominal wall, pelvis, urinary tract, genitalia, anus, and spine. The vast majority of BEEC cases are classified as non-syndromic and the etiology of this malformation is still unknown. This review presents the current knowledge on this multifactorial disorder, including phenotypic and anatomical characterization, epidemiology, proposed developmental mechanisms, existing animal models, and implicated genetic and environmental components.

Experiencia en el abordaje de pacientes con complejo extrofia-epispadias en un centro de alto nivel de complejidad en Colombia, 10 años

Objetivos El complejo extrofia-epispadias (CEE) se considera una de las malformaciones más severas de la línea media de compromiso multisistémico. La extrofia vesical es la presentación más frecuente en el espectro del complejo. Esta patología tiene un alto impacto en la calidad de vida. A pesar de la relación entre un cierre primario temprano y mejores resultados, en nuestro medio la remisión es tardía y la experiencia es escasa. El objetivo del siguiente estudio es mostrar la experiencia en el abordaje de CEE en los últimos 10 años en una institución de alto nivel de complejidad y remisión en Colombia.

Materiales y métodos Se realiza un estudio observacional descriptivo, con una serie de casos del 2006 al 2016.

Resultados En 10 años, se presentaron 5 casos de CEE en un centro de alta complejidad y remisión en Colombia. La mayoría de los pacientes han tenido múltiples intervenciones; la edad del primer procedimiento fue 829 días en promedio (27,6 meses). Se ha tenido un seguimiento postoperatorio promedio de 2,8 años. No se han presentado neoplasias en el seguimiento. Las comorbilidades más frecuentes son infección y litiasis. Ninguno de los pacientes contactados reportó inicio de vida sexual. La escala International Consultation on Incontinence Questionnaire-Urinary Incontinence-Short Form (ICIQ-UI-SF) tuvo un promedio de 9 puntos. Existen factores sociales asociados en nuestro medio.

Conclusión El CEE requiere un abordaje temprano y multidisciplinario en instituciones con experiencia; los resultados en continencia urinaria, función sexual, desarrollo psicosocial y calidad de vida están sujetos a tratamiento oportuno de la patología.

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

Cloacal exstrophy (CE) and persistent cloaca (PC) (alternatively termed urorectal septum malformation sequence [URSMS]), represent two major cloacal defects (CDs). Clinical characteristics and risk factors often are studied for both defects combined, rather than exploring if these defects have different etiologies. We enumerated clinical features for 47 CE and 54 PC (inclusive of URSMS) cases from the National Birth Defects Prevention Study. Thirty-three CE cases were classified as isolated and 14 as multiple (presence of unassociated major defects); respective totals for PC cases were 26 and 28. We compared selected child and maternal characteristics between 11,829 non-malformed controls and CE and PC cases using chi-square or Fisher's exact tests. Compared to controls, CE and PC cases were statistically more likely (p < 0.05) to be preterm; CE cases were more likely to be multiple births. We conducted logistic regression analysis to estimate odds ratios and 95% confidence intervals for any CD, CE, and PC with selected self-reported maternal prepregnancy and periconceptional (one month prior to 3 months following conception) exposures. In crude and adjusted analyses, we observed significant positive associations for any CD, CE, and PC with use of any fertility medication or assisted reproductive technology procedure. Significant positive associations observed only in crude analyses were any CD with maternal obesity or use of progesterone, any CD and CE with any x-ray, and any CD and PC with use of folate antagonist medications. Our findings provide some of the first insights into potential differing etiologies for CE and PC.

Role of the LF-SINE-Derived Distal ISL1 Enhancer in Patients with Classic Bladder Exstrophy

A genome-wide association study and meta-analysis identified ISL1 as the first genome-wide significant susceptibility gene for classic bladder exstrophy (CBE). A short interspersed repetitive element (SINE), first detected in lobe-finned fishes (LF-SINE), was shown to drive Isl1 expression in embryonic mouse genital eminence. Hence, we assumed this enhancer a conclusive target for mutations associated with CBE formation and analyzed a cohort of 200 CBE patients. Although we identified two enhancer variants in five CBE patients, their clinical significance seems unlikely, implying that sequence variants in the ISL1 LF-SINE enhancer are not frequently associated with CBE.

Maternal and fetal risk factors for bladder exstrophy: A nationwide Swedish case-control study

INTRODUCTION

Bladder exstrophy is a rare, congenital, complex malformation where the underlying cause is largely unknown. Both environmental and genetic mechanisms are thought to be involved. There are divergent results concerning the prevalence, birth descriptive data, and potential maternal risk factors for bladder exstrophy. Few previous studies have reflected nationwide populations, population registers, or spanned a longer period of time.

OBJECTIVE

To describe and assess bladder exstrophy and the potential maternal risk factors, for a time period of four decades, by conducting a nationwide register study of bladder exstrophy in Sweden.

METHODS

A matched-design, case-control, linkage-analysis study nested within the entire pool of live births in Sweden between 1973 and 2011 was performed. Cases with bladder exstrophy were identified using nationwide population-based birth and health registers. Inclusion criteria were people born in Sweden with the classification of bladder exstrophy according to the ICD coding system. Cases were matched with five controls per patient, based on birth year and sex. Prevalence was assessed and birth descriptive data were compiled. Potential maternal risk factors were obtained from medical birth registers of cases and assessed using conditional and multivariate logistic regression models to obtain odds ratios as a measure of the relative risk. Classification of the diagnosis in the registers constituted a possible limitation for determining the correct study population, which demanded strict validation and inclusion criteria. All data were collected prospectively, thereby avoiding potential recall bias.

RESULTS

The prevalence was calculated to be approximately 3 per 100,000 live births, with a male-to-female ratio of 1.14:1. In 92.5% of the cases, bladder exstrophy was an isolated malformation without associated major malformations. However, 41% had had surgery for congenital inguinal hernia and 11% of the male subjects had been operated on for cryptorchidism. A significantly higher proportion of cases had a birth weight <1500 g compared with controls, but other characteristics were comparable with controls. High maternal age was the only significant potential associated maternal risk factor.

CONCLUSIONS

One hundred and twenty children born with bladder exstrophy in Sweden during the last four decades were identified; this resulted in prevalence in Sweden of 3 per 100,000. The prevalence was stable over time and the sex ratio was equal. Birth characteristics were comparable to controls, and bladder exstrophy generally occurred as an isolated malformation without major associated malformations. Advanced maternal age was the only significant potential maternal risk factor.

Genetics of Bladder-Exstrophy-Epispadias Complex (BEEC): Systematic Elucidation of Mendelian and Multifactorial Phenotypes

The Bladder-Exstrophy-Epispadias Complex (BEEC) represents the severe end of the uro-rectal malformation spectrum, and has a profound impact on continence, and on sexual and renal function. While previous reports of familial occurrence, in-creased recurrence among first-degree relatives, high concordance rates among monozygotic twins, and chromosomal aberra-tions were suggestive of causative genetic factors, the recent identification of copy number variations (CNVs), susceptibility regions and genes through the systematic application of array based analysis, candidate gene and genome-wide association studies (GWAS) provide strong evidence. These findings in human BEEC cohorts are underscored by the recent description of BEEC(-like) murine knock-out models. Here, we discuss the current knowledge of the potential molecular mechanisms, mediating abnormal uro-rectal development leading to the BEEC, demonstrating the importance of ISL1-pathway in human and mouse and propose SLC20A1 and CELSR3 as the first BEEC candidate genes, identified through systematic whole-exome sequencing (WES) in BEEC patients.

Genome-wide association study and meta-analysis identify ISL1 as genome-wide significant susceptibility gene for bladder exstrophy

The bladder exstrophy-epispadias complex (BEEC) represents the severe end of the uro-rectal malformation spectrum, and is thought to result from aberrant embryonic morphogenesis of the cloacal membrane and the urorectal septum. The most common form of BEEC is isolated classic bladder exstrophy (CBE). To identify susceptibility loci for CBE, we performed a genome-wide association study (GWAS) of 110 CBE patients and 1,177 controls of European origin. Here, an association was found with a region of approximately 220kb on chromosome 5q11.1. This region harbors the ISL1 (ISL LIM homeobox 1) gene. Multiple markers in this region showed evidence for association with CBE, including 84 markers with genome-wide significance. We then performed a meta-analysis using data from a previous GWAS by our group of 98 CBE patients and 526 controls of European origin. This meta-analysis also implicated the 5q11.1 locus in CBE risk. A total of 138 markers at this locus reached genome-wide significance in the meta-analysis, and the most significant marker (rs9291768) achieved a P value of 2.13 × 10-12. No other locus in the meta-analysis achieved genome-wide significance. We then performed murine expression analyses to follow up this finding. Here, Isl1 expression was detected in the genital region within the critical time frame for human CBE development. Genital regions with Isl1 expression included the peri-cloacal mesenchyme and the urorectal septum. The present study identified the first genome-wide significant locus for CBE at chromosomal region 5q11.1, and provides strong evidence for the hypothesis that ISL1 is the responsible candidate gene in this region.