Enrika Bartels

Whole-exome resequencing reveals recessive mutations in TRAP1 in individuals with CAKUT and VACTERL association

Congenital abnormalities of the kidney and urinary tract (CAKUT) account for approximately half of children with chronic kidney disease and they are the most frequent cause of end-stage renal disease in children in the US. However, its genetic etiology remains mostly elusive. VACTERL association is a rare disorder that involves congenital abnormalities in multiple organs including the kidney and urinary tract in up to 60% of the cases. By homozygosity mapping and whole exome resequencing combined with high-throughput mutation analysis by array-based multiplex PCR and next-generation sequencing, we identified recessive mutations in the gene TNF receptor-associated protein 1 (TRAP1) in two families with isolated CAKUT and three families with VACTERL association. TRAP1 is a heat shock protein 90-related mitochondrial chaperone possibly involved in antiapoptotic and endoplasmic reticulum-stress signaling. Trap1 is expressed in renal epithelia of developing mouse kidney E13.5 and in the kidney of adult rats, most prominently in proximal tubules and in thick medullary ascending limbs of Henle’s loop. Thus, we identified mutations in TRAP1 as highly likely causing CAKUT or CAKUT in VACTERL association.

Research perspectives in the etiology of congenital anorectal malformations using data of the International Consortium on Anorectal Malformations: evidence for risk factors across different populations

PurposeThe recently established International Consortium on Anorectal Malformations aims to identify genetic and environmental risk factors in the etiology of syndromic and nonsyndromic anorectal malformations (ARM) by promoting collaboration through data sharing and combined research activities.MethodsThe consortium attempts to recruit at least 1,000 ARM cases. DNA samples are collected from case–parent triads to identify genetic factors involved in ARM. Several genetic techniques will be applied, including SNP arrays, gene and whole exome sequencing, and a genome-wide association study. Questionnaires inquiring about circumstances before and during pregnancy will be used to obtain environmental risk factor data.ResultsCurrently, 701 ARM cases have been recruited throughout Europe. Clinical data are available from all cases, and DNA samples and questionnaire data mainly from the Dutch and German cases. Preliminary analyses on environmental risk factors in the Dutch and German cohort found associations between ARM and family history of ARM, fever during first trimester of pregnancy and maternal job exposure to cleaning agents and solvents.ConclusionFirst results show that both genetic and environmental factors may contribute to the multifactorial etiology of ARM. The International Consortium on Anorectal Malformations will provide possibilities to study and detect important genes and environmental risk factors for ARM, ultimately resulting in better genetic counseling, improved therapies, and primary prevention.

Microduplications at 22q11.21 are associated with non-syndromic classic bladder exstrophy

The exstrophy-epispadias complex (EEC) comprises a spectrum of urogenital anomalies in which part or all of the distal urinary tract fails to close. The present study aimed to identify microaberrations characterized by loss or gain of genomic material that contribute to the EEC at a genome-wide level. Molecular karyotyping, utilizing 549,839 single nucleotide polymorphisms (SNPs) with an average spacing of 5.7 kilobases, was performed to screen an initial cohort of 16 patients with non-syndromic EEC. A de novo microduplication involving chromosomal region 22q11.21 was identified in one patient with classic exstrophy of the bladder (CBE). Subsequent multiplex ligation-dependent probe amplification (MLPA) analysis was performed with an MLPA 22q11 kit in a further 50 non-syndromic EEC cases. We identified one CBE patient with an overlapping 22q11.21 duplication in whom the duplication had been transmitted from the unaffected mother. Chromosomal region 22q11 is well known for its susceptibility to genomic rearrangements, and these are associated with various syndromes including the velo-cardio-facial/DiGeorge syndrome (VCFS/DGS), the der(22) syndrome, and the cat-eye syndrome. Duplications in this region result in a wide and variable spectrum of clinical presentations that include features of the VCFS/DGS, while some carriers present with a completely normal phenotype. Our findings extend the phenotypic spectrum of the 22q11.2 duplication syndrome, and indicate that this aberration predisposes to CBE with incomplete penetrance.

De novo microduplications at 1q41, 2q37.3, and 8q24.3 in patients with VATER/VACTERL association

The acronym VATER/VACTERL association describes the combination of at least three of the following congenital anomalies: vertebral defects (V), anorectal malformations (A), cardiac defects (C), tracheoesophageal fistula with or without esophageal atresia (TE), renal malformations (R), and limb defects (L). We aimed to identify highly penetrant de novo copy number variations (CNVs) that contribute to VATER/VACTERL association. Array-based molecular karyotyping was performed in a cohort of 41 patients with VATER/VACTERL association and 6 patients with VATER/VACTERL-like phenotype including all of the patients’ parents. Three de novo CNVs were identified involving chromosomal regions 1q41, 2q37.3, and 8q24.3 comprising one (SPATA17), two (CAPN10, GPR35), and three (EPPK1, PLEC, PARP10) genes, respectively. Pre-existing data from the literature prompted us to choose GPR35 and EPPK1 for mouse expression studies. Based on these studies, we prioritized GPR35 for sequencing analysis in an extended cohort of 192 patients with VATER/VACTERL association and VATER/VACTERL-like phenotype. Although no disease-causing mutation was identified, our mouse expression studies suggest GPR35 to be involved in the development of the VATER/VACTERL phenotype. Follow-up of GPR35 and the other genes comprising the identified duplications is warranted.

Assisted reproductive techniques and the risk of anorectal malformations: a German case-control study

BackgroundThe use of assisted reproductive techniques (ART) for treatment of infertility is increasing rapidly worldwide. However, various health effects have been reported including a higher risk of congenital malformations. Therefore, we assessed the risk of anorectal malformations (ARM) after in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).MethodsData of the German Network for Congenital Uro-REctal malformations (CURE-Net) were compared to nationwide data of the German IVF register and the Federal Statistical Office (DESTATIS). Odds ratios (95% confidence intervals) were determined to quantify associations using multivariable logistic regression accounting for potential confounding or interaction by plurality of births.ResultsIn total, 295 ARM patients born between 1997 and 2011 in Germany, who were recruited through participating pediatric surgeries from all over Germany and the German self-help organisation SoMA, were included. Controls were all German live-births (n = 10,069,986) born between 1997 and 2010. Overall, 30 cases (10%) and 129,982 controls (1%) were born after IVF or ICSI, which translates to an odds ratio (95% confidence interval) of 8.7 (5.9–12.6) between ART and ARM in bivariate analyses. Separate analyses showed a significantly increased risk for ARM after IVF (OR, 10.9; 95% CI, 6.2–19.0; P < 0.0001) as well as after ICSI (OR, 7.5; 95% CI, 4.6–12.2; P < 0.0001). Furthermore, separate analyses of patients with isolated ARM, ARM with associated anomalies and those with a VATER/VACTERL association showed strong associations with ART (ORs 4.9, 11.9 and 7.9, respectively). After stratification for plurality of birth, the corresponding odds ratios (95% confidence intervals) were 7.7 (4.6–12.7) for singletons and 4.9 (2.4–10.1) for multiple births.ConclusionsThere is a strongly increased risk for ARM among children born after ART. Elevations of risk were seen after both IVF and ICSI. Further, separate analyses of patients with isolated ARM, ARM with associated anomalies and those with a VATER/VACTERL association showed increased risks in each group. An increased risk of ARM was also seen among both singletons and multiple births.

De novo 13q deletions in two patients with mild anorectal malformations as part of VATER/VACTERL and VATER/VACTERL-like association and analysis of EFNB2 in patients with anorectal malformations

Anorectal malformations (ARMs) comprise a broad spectrum of conditions ranging from mild anal anomalies to complex cloacal malformations. In 40–50% of cases, ARM occurs within the context of defined genetic syndromes or complex multiple congenital anomalies, such as VATER/VACTERL (vertebral defects [V], ARMs [A], cardiac defects [C], tracheoesophageal fistula with or without esophageal atresia [TE], renal malformations [R], and limb defects [L]) association. Here, we report the identification of deletions at chromosome 13q using single nucleotide polymorphism‐based array analysis in two patients with mild ARM as part of VATER/VACTERL and VATER/VACTERL‐like associations. Both deletions overlap the previously defined critical region for ARM. Heterozygous Efnb2 murine knockout models presenting with mild ARM suggest EFNB2 as an excellent candidate gene in this region. Our patients showed a mild ARM phenotype, closely resembling that of the mouse. We performed a comprehensive mutation analysis of the EFNB2 gene in 331 patients with isolated ARM, or ARM as part of VATER/VACTERL or VATER/VACTERL‐like associations. However, we did not identify any disease‐causing mutations. Given the convincing argument for EFNB2 as a candidate gene for ARM, analyses of larger samples and screening of functionally relevant non‐coding regions of EFNB2 are warranted. In conclusion, our report underlines the association of chromosome 13q deletions with ARM, suggesting that routine molecular diagnostic workup should include the search for these deletions. Despite the negative results of our mutation screening, we still consider EFNB2 an excellent candidate gene for contributing to the development of ARM in humans.

Phenotype severity in the bladder exstrophy-epispadias complex: Analysis of genetic and nongenetic contributing factors in 441 families from North America and Europe

OBJECTIVE To identify genetic and nongenetic risk factors that contribute to the severity of the bladder exstrophy-epispadias complex (BEEC). STUDY DESIGN Patients with BEEC from North America (n = 167) and Europe (n = 274) were included. The following data were collected: associated anomalies, parental age at conception, mode of conception, periconceptional folic acid supplementation, maternal risk factors during pregnancy, and environmental risk factors. The patients were divided into 3 subgroups according to phenotype severity: (i) mild, epispadias (n = 43); (ii) intermediate, classic bladder exstrophy (n = 366); and (iii) severe, cloacal exstrophy (n = 31). These subgroups then were compared with identify factors that contribute to phenotype severity. RESULTS Males were overrepresented in all subgroups. A relatively high prevalence of cleft lip, with or without cleft palate, was observed. Maternal smoking and medical radiation during the first trimester were associated with the severe cloacal exstrophy phenotype. Compliance with periconceptional folic acid supplementation was associated with the mildest phenotype (epispadias). CONCLUSIONS Periconceptional folic acid supplementation appears to prevent the development of the severe phenotype of BEEC.

Familial occurrence of the VATER/VACTERL association

The acronym VATER/VACTERL association is used to describe the non-random co-occurrence of vertebral defects (V), anorectal malformations (A), cardiac defects (C), tracheo-esophageal fistula with or without esophageal atresia (TE), renal malformations (R), and limb defects (L). We report a familial case of VATER/VACTERL association in which both the index case and her maternal uncle displayed four major component features of the disorder. A systematic literature search identified 12 previously described familial cases. However, on comparison, both members fulfilled the diagnostic criteria for VATER/VACTERL association only in one instance, and ours is the second such report. Although, a SNP array-based analysis identified no causal genomic alteration, the findings in the present family suggest that genetic factors are implicated in the development of the disorder.

De novo duplication of 18p11.21–18q12.1 in a female with anorectal malformation

De Novo Duplication of 18p11.21–18q12.1 in a Female With Anorectal Malformation Charlotte Schramm, Markus Draaken, Enrika Bartels, Thomas M. Boemers, Eberhard Schmiedeke, Sabine Grasshoff-Derr, Stefanie M€arzheuser, Stuart Hosie, Stefan Holland-Cunz, Friederike Baudisch, Lutz Priebe, Per Hoffmann, Alexander M. Zink, Hartmut Engels, Felix F. Brockschmidt, Stefan Aretz, Markus M. N€othen, Michael Ludwig, and Heiko Reutter* Institute of Human Genetics, University of Bonn, Bonn, Germany Department of Genomics, Life and Brain Center, University of Bonn, Bonn, Germany Department of Pediatric Surgery and Pediatric Urology, Children’s Hospital, Cologne, Germany Department of Pediatric Surgery and Urology, Center for Child and Adolescent Health, Hospital Bremen-Mitte, Bremen, Germany Department of Pediatric Surgery, University Hospital W€urzburg, W€urzburg, Germany Department of Pediatric Surgery, Campus Virchow Clinic, Charit e University Hospital Berlin, Berlin, Germany Department of Pediatric Surgery, Klinikum Schwabing, Technische Universit€at M€unchen, M€unchen, Germany Department of Pediatric Surgery, University of Heidelberg, Heidelberg, Germany Department of Clinical Chemistry and Clinical Pharmacology, University of Bonn, Bonn, Germany Department of Neonatology, Children’s Hospital, University of Bonn, Bonn, Germany

Genome-wide association study and mouse expression data identify a highly conserved 32 kb intergenic region between WNT3 and WNT9b as possible susceptibility locus for isolated classic exstrophy of the bladder

Bladder exstrophy-epispadias complex (BEEC), the severe end of the urorectal malformation spectrum, has a profound impact on continence as well as sexual and renal functions. It is widely accepted that for the majority of cases the genetic basis appears to be multifactorial. Here, we report the first study which utilizes genome-wide association methods to analyze a cohort comprising patients presenting the most common BEEC form, classic bladder exstrophy (CBE), to identify common variation associated with risk for isolated CBE. We employed discovery and follow-up samples comprising 218 cases/865 controls and 78 trios in total, all of European descent. Our discovery sample identified a marker near SALL1, showing genome-wide significant association with CBE. However, analyses performed on follow-up samples did not add further support to these findings. We were also able to identify an association with CBE across our study samples (discovery: P = 8.88 × 10(-5); follow-up: P = 0.0025; combined: 1.09 × 10(-6)) in a highly conserved 32 kb intergenic region containing regulatory elements between WNT3 and WNT9B. Subsequent analyses in mice revealed expression for both genes in the genital region during stages relevant to the development of CBE in humans. Unfortunately, we were not able to replicate the suggestive signal for WNT3 and WNT9B in a sample that was enriched for non-CBE BEEC cases (P = 0.51). Our suggestive findings support the hypothesis that larger samples are warranted to identify association of common variation with CBE.