Exclusion of the Sonic Hedgehog gene as responsible for Currarino syndrome and anorectal malformations with sacral hypodevelopment

Currarino syndrome: a comprehensive genetic review of a rare congenital disorder

Background

The triad of a presacral mass, sacral agenesis and an anorectal anomaly constitutes the rare Currarino syndrome (CS), which is caused by dorsal–ventral patterning defects during embryonic development. The major causative CS gene is MNX1, encoding a homeobox protein.

Main body

In the majority of patients, CS occurs as an autosomal dominant trait; however, a female predominance observed, implies that CS may underlie an additional mode(s) of inheritance. Often, the diagnosis of CS is established solely by clinical findings, impacting a detailed analysis of the disease. Our combined data, evaluating more than 60 studies reporting patients with CS-associated mutations, revealed a slightly higher incidence rate in females with a female-to-male ratio of 1.39:1. Overall, MNX1 mutation analysis was successful in only 57.4% of all CS patients investigated, with no mutation detected in 7.7% of the familial and 68% of the sporadic patients. Our studies failed to detect the presence of an expressed MNX1 isoform that might explain at least some of these mutation-negative cases.

Conclusion

Aside from MNX1, other genes or regulatory regions may contribute to CS and we discuss several cytogenetic studies and whole-exome sequencing data that have implicated further loci/genes in its etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01799-0.

Exome chip association study excluded the involvement of rare coding variants with large effect sizes in the etiology of anorectal malformations

INTRODUCTION

Anorectal malformations (ARM) are rare congenital malformations, resulting from disturbed hindgut development. A genetic etiology has been suggested, but evidence for the involvement of specific genes is scarce. We evaluated the contribution of rare and low-frequency coding variants in ARM etiology, assuming a multifactorial model.

METHODS

We analyzed 568 Caucasian ARM patients and 1,860 population-based controls using the Illumina HumanExome Beadchip array, which contains >240,000 rare and low-frequency coding variants. GenomeStudio clustering and calling was followed by re-calling of 'no-calls' using zCall for patients and controls simultaneously. Single variant and gene-based analyses were performed to identify statistically significant associations, applying Bonferroni correction. Following an extra quality control step, candidate variants were selected for validation using Sanger sequencing.

RESULTS

When we applied a MAF of ≥1.0%, no variants or genes showed statistically significant associations with ARM. Using a MAF cut-off at 0.4%, 13 variants initially reached statistical significance, but had to be discarded upon further inspection: ten variants represented calling errors of the software, while the minor alleles of the remaining three variants were not confirmed by Sanger sequencing.

CONCLUSION

Our results show that rare and low-frequency coding variants with large effect sizes, present on the exome chip do not contribute to ARM etiology.

Genetic and nongenetic etiology of nonsyndromic anorectal malformations: a systematic review

Congenital anorectal malformations (ARMs) are one of the most frequently observed birth defects of the digestive system. However, their etiology remains elusive. Therefore, we aim to summarize and critically appraise all existing literature on the genetic and nongenetic etiology of nonsyndromic ARM and to conclude with unifying hypotheses and directions for future research. A structured literature search on English language human studies was conducted in PubMed and Embase up to October 1, 2013, resulting in 112 included articles. Research on the identification of genes underlying nonsyndromic ARM is remarkably scarce. Most studies were focused on screening of candidate genes for mutations or single-nucleotide polymorphisms, which did not yield any substantial evidence. Nongenetic factors fairly consistently found to be associated with ARM are assisted reproductive techniques, multiple pregnancy, preterm delivery, low birth weight, maternal overweight or obesity, and preexisting diabetes. This review provides indications for the involvement of both genes and nongenetic risk factors in the etiology of ARM. In future studies, large cohorts of patients with ARM from national and international collaborations are needed to acquire new hypotheses and knowledge through hypothesis-generating approaches. Challenges for future studies may also lie in the investigation of gene-gene and gene-environment interactions.

Associations of anorectal malformations and related syndromes

Anorectal malformations (ARMs) represent a complex group of congenital anomalies resulting from abnormal development of the hindgut, allantois and Mullerian duct resulting in complete or partial urorectal septal malformations. There is a wide variety of phenotypic expression, ranging from mild anorectal to very complex severe ARM with >75 % having other associated malformations. 50 % of cases are syndromic although many may have other associated anomalies. This suggests a genetic link but the genetics of ARM are highly complex with a number of candidate genes being identified. Many can be classified as "field defects" as a result of a complex set of genetic interactions. Patients with associated malformations can be classified into those with multiple congenital anomalies (non-syndromic), those with chromosomal abnormalities and those with non-chromosomal syndromic associations, also, those with non-chromosomal syndromes and the influence of environmental factors (e.g. drugs in pregnancy). Although much is not known about the aetiology of ARM, the weight of evidence points to genetic factors as major causes for the condition. In this review, we look at the chromosomal and genetic associations and their underlying signalling pathways, to obtain a better understanding of the pathogenetic mechanisms involved in developing ARM. The spectrum of ARM phenotypic expression probably results from involvement and crosstalk between a number of critical signalling systems involved in development of this region. As a result, it may be expressed as a "field developmental defect" with many associated abnormalities. The role of environmental factors in the development of ARM is probably less.

Involvement of the WNT and FGF signaling pathways in non-isolated anorectal malformations: sequencing analysis of WNT3A, WNT5A, WNT11, DACT1, FGF10, FGFR2 and the T gene

Anorectal malformations (ARMs) comprise a broad spectrum of anomalies, including anal atresia, congenital anal fistula and persistence of the cloaca. Research suggests that genetic factors play an important role in ARM development. However, few genetic variants have been identified. Embryogenesis is orchestrated by crosstalk of the wingless-type MMTV integration site family (WNT) and fibroblast growth factor (FGF) signaling pathways in a process that involves several intracellular cascades. Studies in mice have implicated several genes from these pathways in the etiology of ARMs. We performed sequencing analysis of seven of these previously reported genes in 78 patients with ARMs occurring within the context of at least one additional congenital anomaly. No associations were identified with variants in WNT3A, WNT5A, WNT11, DACT1, FGF10 or the T gene. In the FGFR2 gene, three novel heterozygous nucleotide substitutions were identified. Further investigations, including the study of family members, revealed that these variants were not causally related to the phenotype in the present ARM cohort. Mutations in the seven investigated genes may nonetheless be a cause of ARMs in rare cases. However, further studies should consider genes encoding other proteins in the WNT/FGF signaling pathways as possible candidates.

Currarino Syndroma, initially misdiagnosed and treated like megacolon congenitum

Currarino syndrome was first described as a triad by Guido Currarino, an American radiologist in 1981. It is an autosomal dominant hereditary disease known by the triad of anorectal stenosis, anterior sacral defect, and a presacral mass that is most often an anterior sacral meningocele.

We represent a 3 year boy with refractory constipation from birth, which had been wrongly diagnosed and treated as Hirschsprung’s disease since early childhood. The patient underwent urgent colostomy because of water intoxication due to bowel irrigation, and following investigations (CT, MRI) revealed anorectal anomaly and presacral mass compatible with Curarrino’s syndrome.

Definitive operation was done with perineal approach, posterior sagittal anorectoplasty, with interval colostomy closure 2 months after perineal operation. An uncomplicated postoperative recovery ensued. The patient’s bowel habits successfully returned to normal soon after the operation. A multidisciplinary diagnostic and therapeutic protocol is presented. Main points are rectal examination, sacrum x-Ray, molecular genetic diagnosis, radiologic evaluation of every member of Currarino syndrome families, CT scan, magnetic resonance (MR) evaluation of patient spine and pelvis and suction rectal biopsies. If the mass is a meningocele, colostomy and neurosurgical exploration should precede anoplasty due to the risk of meningitis.

Congenital gastrointestinal anomalies in anorectal malformations: what relationship and management?

To date, no systematic review of gastrointestinal anomalies associated with anorectal malformations has been performed. We report the management of three challenging cases of neonates affected by congenital gastrointestinal and anorectal malformations and we review the pertinent published reports to disclose the incidence and outcome of this combination. In 3951 anorectal malformations, the incidence of digestive tract anomalies was approximately 15%. The association of multiple congenital gastrointestinal defects strongly increased the case complexity and worsened the outcome. Based on our study, the application of a rational and staged management plan provides easier diagnosis and treatment of complex cases. Moreover, keeping in mind the likely co-occurrence of anorectal and gastrointestinal anomalies could help avoid misdiagnosis and prevent life-threatening complications. Finally, the knowledge of this association and its successful management can help the multi-specialist team to become more confident in counselling, diagnosis and treatment.

Reconstruction of a functional human gene network, with an application for prioritizing positional candidate genes

Most common genetic disorders have a complex inheritance and may result from variants in many genes, each contributing only weak effects to the disease. Pinpointing these disease genes within the myriad of susceptibility loci identified in linkage studies is difficult because these loci may contain hundreds of genes. However, in any disorder, most of the disease genes will be involved in only a few different molecular pathways. If we know something about the relationships between the genes, we can assess whether some genes (which may reside in different loci) functionally interact with each other, indicating a joint basis for the disease etiology. There are various repositories of information on pathway relationships. To consolidate this information, we developed a functional human gene network that integrates information on genes and the functional relationships between genes, based on data from the Kyoto Encyclopedia of Genes and Genomes, the Biomolecular Interaction Network Database, Reactome, the Human Protein Reference Database, the Gene Ontology database, predicted protein-protein interactions, human yeast two-hybrid interactions, and microarray co-expressions. We applied this network to interrelate positional candidate genes from different disease loci and then tested 96 heritable disorders for which the Online Mendelian Inheritance in Man database reported at least three disease genes. Artificial susceptibility loci, each containing 100 genes, were constructed around each disease gene, and we used the network to rank these genes on the basis of their functional interactions. By following up the top five genes per artificial locus, we were able to detect at least one known disease gene in 54% of the loci studied, representing a 2.8-fold increase over random selection. This suggests that our method can significantly reduce the cost and effort of pinpointing true disease genes in analyses of disorders for which numerous loci have been reported but for which most of the genes are unknown.

Molecular genetic analysis of a de novo balanced translocation t(6;17)(p21.31;q11.2) associated with hypospadias and anorectal malformation

We report a young boy with penoscrotal hypospadias, anal atresia (AA) with a recto-urethral fistula, a hypoplastic kidney and a balanced translocation t(6;17)(p21.31;q11.2). Physical mapping of the breakpoints localized the chromosome 6 breakpoint within an intron of the gene lipoma HMGIC fusion partner-like 5 (LHFPL5) whereas the chromosome 17 breakpoint was mapped to the first intron of the 182-FIP gene encoding the Fragile X Mental Retardation Protein Interacting Protein. Sequence analysis across the breakpoints revealed an almost perfectly balanced translocation with a 2 bp deletion on the derivative chromosome 6 and a 7 bp duplication on the derivative chromosome 17. We identified a fusion transcript consisting of the first exon of 182-FIP and the last exon of LHFPL5 in patient-derived cells. Quantitative expression analysis of the genes flanking the breakpoints, revealed increased transcript levels for SFRS protein kinase 1 (SRPK1) and TAO kinase 1 (TAOK1) which suggests a positional effect due to the translocation. We hypothesize that the urogenital and anorectal malformations in the patient result from one or several mechanisms including disruption of the genes 182-FIP and LHFPL5, altered expression of the genes flanking the translocation breakpoints and, a gain of function mechanism mediated by the 182-FIP-LHFPL5 fusion transcript.

New clinical and therapeutic perspectives in Currarino syndrome (study of 29 cases)

PURPOSE

The aim of the study was to clearly define the anomalies that compose the Currarino syndrome (CS). We highlight the frequency of associated malformations of the spinal cord and the possibility of a communication between the presacral tumor and the spinal canal, leading to neurological complications.

METHODS

We studied 29 patients with CS, including 12 familial cases; histological examination of the presacral tumor was performed, and cytogenetic and molecular biology studies of the HLXB9 locus were carried out.

RESULTS

All except 2 patients had a sacral malformation; 23 had an anorectal anomaly and 8 had isolated chronic intestinal pseudo-obstruction. There were 20 presacral tumors, one of which was malignant. There was a communication between the presacral tumor and the spinal canal in 12 cases, and tethering of the spinal cord in 17 cases. Twenty-five patients underwent surgery with a single-stage operation for 7, on both the intestinal and the presacral malformations, and, when required, the spinal cord anomalies. Twelve patients harbored a heterozygous point mutation of the coding sequence of HLXB9 gene.

CONCLUSION

By accurate evaluation of the 4 main features in the CS, the correct surgical management, including neurosurgery, can be performed in a 1-stage approach.

Genomewide scan for anal atresia in swine identifies linkage and association with a chromosome region on Sus scrofa chromosome 1

Anal atresia is a rare and severe disorder in swine occurring with an incidence of 0.1-1.0%. A whole-genome scan based on affected half-sibs was performed to identify susceptibility loci for anal atresia. The analysis included 27 families with a total of 95 animals and 65 affected piglets among them. Animals were genotyped for 126 microsatellite markers distributed across the 18 autosomal porcine chromosomes and the X chromosome, covering an estimated 2080 cM. Single-point and multipoint nonparametric linkage scores were calculated using the computer package ALLEGRO 1.0. Significant linkage results were obtained for chromosomes 1, 3, and 12. Markers on these chromosomes and additionally on chromosomes for which candidate genes have been postulated in previous studies were subjected to the transmission disequilibrium test (TDT). The test statistic exceeded the genomewide significance level for adjacent markers SW1621 (P = 7 x 10(-7)) and SW1902 (P = 3 x 10(-3)) on chromosome 1, supporting the results of the linkage analysis. A specific haplotype associated with anal atresia that could prove useful for selection against the disorder was revealed. Suggestive linkage and association were also found for markers S0081 on chromosome 9 and SW957 on chromosome 12.

Rectal duplication cyst presenting as perianal sepsis: report of two cases and review of the literature

INTRODUCTION

Recurrent perianal sepsis is a difficult problem to manage in colorectal surgical practice. One cause is rectal duplication cyst, a rare congenital lesion that is easily overlooked. Many cases have associated congenital defects, especially musculoskeletal anomalies, and may provide a clue to the underlying condition. Early diagnosis is important because these cysts do not resolve spontaneously and may undergo malignant change.

METHODS

We present two cases of middle-aged females who presented with perianal sepsis secondary to rectal duplication cyst. The first case had numerous surgical procedures for a perianal fistula during a ten-year period. She had associated sacral anomalies consistent with Currarino syndrome. The second case presented with a perineal mass after a bout of perianal inflammation. Both cases had the entire cyst surgically excised.

RESULTS

There were no complications postoperatively and no recurrence at follow-up. Histopathology revealed no malignancy in the cyst.

CONCLUSIONS

Rectal duplication cyst is a rare cause of recurrent perianal sepsis that should be considered in difficult cases, especially in those with associated musculoskeletal anomalies. Complete surgical excision is the preferred treatment to prevent recurrence and the risk of malignant degeneration.

Currarino syndrome: proposal of a diagnostic and therapeutic protocol

BACKGROUND/PURPOSE

The Currarino syndrome (CS) is a peculiar form of caudal regression syndrome (CRS) characterized by the association of hemisacrum, anorectal malformation (ARM), and presacral mass. The authors analyzed retrospectively their series, and they propose a multidisciplinary diagnostic and therapuetic protocol that until now has not been introduced.

METHODS

A series of 6 patients with CS is presented. Five of them were treated initially in other centers. None of them had an early diagnosis. All presented associated anomalies; in 50%, Hirschsprung's disease (HD) and other dysganglionoses were present. One patient died of a presacral ectopic nephroblastoma.

RESULTS

Depending on the expressivity, 3 types of CS can be identified, complete, mild, and minimal. Dysganglionoses and HD can be considered part of CS. A multidisciplinary diagnostic and therapeutic protocol is presented. Main points are sacrum x-Ray, molecular genetic diagnosis, radiologic evaluation of every member of CS families, magnetic resonance (MR) evaluation of patient spine and pelvis, suction rectal biopsies, and search for associated anomalies.

CONCLUSIONS

This protocol could give a valid contribution to the treatment of CS, allowing an early diagnosis and proposing a rational timing of multidisciplinary surgical procedures. Early diagnosis and treatment are essential to avoid morbidity and mortality from an undiagnosed presacral mass.

Currarino triad associated with Hirschsprung's disease

The Currarino syndrome is a rare hereditary condition. The major symptom is chronic constipation from early life, and, in more than 80% of the cases, this condition is diagnosed in the first decade. The authors describe an unusual case of a complete Currarino triad associated with Hirschsprung's disease in a 6-year-old girl, presenting persistent constipation and abdominal distension. The patient is free of symptoms after surgical treatment of anorectal malformation and Hirschsprung's disease. The presacral mass was excised. Complete screening of the pelvis is recommended by using ultrasonography, computed tomography (CT) scan, and radiography in patients with a history of chronic constipation from early childhood.

Mapping loci causing susceptibility to anal atresia in pigs, using a resource pedigree

BACKGROUND/PURPOSE

Very little information on the genetic background for anal atresia (anorectal malformations; AA) in humans has been described. A strikingly similar natural anomaly occurs in piglets. The authors have used this as an animal model for various research purposes. The affected piglets were treated surgically soon after birth, raised, and used for breeding. The authors have generated a resource pedigree segregating for this naturally occurring nonsyndromal AA and describe here the first attempt to map susceptibility loci by marker analysis.

METHODS

A pig pedigree with a high incidence of AA has been established by selective breeding using 3 probands from the Landrace and Large White breeds. It has been maintained by intrafamilial crossing for more than 15 years. A backcross pedigree has now been generated by mating 4 AA females to an unaffected male from the Chinese Meishan breed. F(1) animals were both intercrossed and backcrossed to affected AA animals. A genome scan was carried out using the F(0), F(1), and affected backcross progeny. Ninety-two microsatellite loci were analyzed using fluorescently labelled primers and an ABI377 sequencer. Linkage analysis was done with the CRI-MAP 2.4 software.

RESULTS

Crossing affected parents increased the incidence of abnormalities from 30% to 61.9%. All 39 F(1) pigs were unaffected. In the F(1) intercross, only 3 of 205 (1.5%) were affected, whereas 42 of 523 (8.0%) backcross progeny were affected. The marked difference in the incidence of affected progeny in the F(1) intercross and in the backcross indicates the presence of multiple genes causing AA. The genome scan showed suggestive evidence for the presence of a susceptibility locus on pig chromosome 15 (lod score 2.7 for a pig microsatellite marker SW2072).

CONCLUSIONS

The results clearly show that AA has a oligogenic or polygenic background. The genome scan showed one suggestive locus causing AA on pig chromosome 15. The long-term goal is to identify causative genes for this malformation by comparative positional candidate cloning. This study provides, for the first time, linkage mapping of nonsyndromal anorectal malformations with a polygenic inheritance.

Anorectal malformations caused by defects in sonic hedgehog signaling

Anorectal malformations are a common clinical problem affecting the development of the distal hindgut in infants. The spectrum of anorectal malformations ranges from the mildly stenotic anus to imperforate anus with a fistula between the urinary and intestinal tracts to the most severe form, persistent cloaca. The etiology, embryology, and pathogenesis of anorectal malformations are poorly understood and controversial. Sonic hedgehog (Shh) is an endoderm-derived signaling molecule that induces mesodermal gene expression in the chick hindgut. However, the role of Shh signaling in mammalian hindgut development is unknown. Here, we show that mutant mice with various defects in the Shh signaling pathway exhibit a spectrum of distal hindgut defects mimicking human anorectal malformations. Shh null-mutant mice display persistent cloaca. Mutant mice lacking Gli2 or Gli3, two zinc finger transcription factors involved in Shh signaling, respectively, exhibit imperforate anus with recto-urethral fistula and anal stenosis. Furthermore, persistent cloaca is also observed in Gli2(-/-);Gli3(+/-), Gli2(+/-);Gli3(-/-), and Gli2(-/-);Gli3(-/-) mice demonstrating a gene dose-dependent effect. Therefore, Shh signaling is essential for normal development of the distal hindgut in mice and mutations affecting Shh signaling produce a spectrum of anorectal malformations that may reveal new insights into their human disease equivalents.

Regulation of osteoblast differentiation mediated by bone morphogenetic proteins, hedgehogs, and Cbfa1

Osteoblasts arise from common progenitors with chondrocytes, muscle and adipocytes, and various hormones and local factors regulate their differentiation. We review here regulation of osteoblast differentiation mediated by the local factors such as bone morphogenetic proteins (BMPs) and hedgehogs and the transcription factor, core-binding factor alpha-1 (Cbfa1). BMPs are the most potent regulators of osteoblast differentiation among the local factors. Sonic and Indian hedgehogs are involved in osteoblast differentiation by interacting with BMPs. Cbfa1, a member of the runt domain gene family, plays a major role in the processes of a determination of osteoblast cell lineage and maturation of osteoblasts. Cbfa1 is an essential transcription factor for osteoblast differentiation and bone formation, because Cbfa1-deficient mice completely lacked bone formation due to maturation arrest ofosteoblasts. Although the regulatory mechanism of Cbfa1 expression has not been fully clarified, BMPs are an important local factor that up-regulates Cbfa1 expression. Thus, the intimate interaction between local factors such as BMPs and hedgehogs and the transcription factor, Cbfa1, is important to osteoblast differentiation and bone formation.