Mutations in SIP1, encoding Smad interacting protein-1, cause a form of Hirschsprung disease

A Novel Partial Duplication of ZEB2 and Review of ZEB2 Involvement in Mowat-Wilson Syndrome

Mowat-Wilson syndrome is a rare genetic condition characterized by intellectual disability, structural anomalies, and dysmorphic features. It is caused by haploinsufficiency of the ZEB2 gene in chromosome 2q22.3. Over 180 distinct mutations in ZEB2 have been reported, including nonsense and missense point mutations, deletions, and large chromosomal rearrangements. We report on a 14-year-old female with a clinical diagnosis of Mowat-Wilson syndrome. Chromosomal microarray identified a novel de novo 69-kb duplication containing exons 1 and 2 of the ZEB2 gene. Sequence analysis identified no other variants in this gene. This is the first report of a partial duplication of the ZEB2 gene resulting in Mowat-Wilson syndrome.

Critical involvement of ZEB2 in collagen fibrillogenesis: the molecular similarity between Mowat-Wilson syndrome and Ehlers-Danlos syndrome

Mowat-Wilson syndrome (MOWS) is a congenital disease caused by de novo heterozygous loss of function mutations or deletions of the ZEB2 gene. MOWS patients show multiple anomalies including intellectual disability, a distinctive facial appearance, microcephaly, congenital heart defects and Hirschsprung disease. However, the skin manifestation(s) of patients with MOWS has not been documented in detail. Here, we recognized that MOWS patients exhibit many Ehlers-Danlos syndrome (EDS)-like symptoms, such as skin hyperextensibility, atrophic scars and joint hypermobility. MOWS patients showed a thinner dermal thickness and electron microscopy revealed miniaturized collagen fibrils. Notably, mice with a mesoderm-specific deletion of the Zeb2 gene (Zeb2-cKO) demonstrated redundant skin, dermal hypoplasia and miniaturized collagen fibrils similar to those of MOWS patients. Dermal fibroblasts derived from Zeb2-cKO mice showed a decreased expression of extracellular matrix (ECM) molecules, such as collagens, whereas molecules involved in degradation of the ECM, such as matrix metalloproteinases (MMPs), were up-regulated. Furthermore, bleomycin-induced skin fibrosis was attenuated in Zeb2-cKO mice. We conclude that MOWS patients exhibit an EDS-like skin phenotype through alterations of collagen fibrillogenesis due to ZEB2 mutations or deletions.

Should I stay or should I go? Cadherin function and regulation in the neural crest

Our increasing comprehension of neural crest cell development has reciprocally advanced our understanding of cadherin expression, regulation, and function. As a transient population of multipotent stem cells that significantly contribute to the vertebrate body plan, neural crest cells undergo a variety of transformative processes and exhibit many cellular behaviors, including epithelial-to-mesenchymal transition (EMT), motility, collective cell migration, and differentiation. Multiple studies have elucidated regulatory and mechanistic details of specific cadherins during neural crest cell development in a highly contextual manner. Collectively, these results reveal that gradual changes within neural crest cells are accompanied by often times subtle, yet important, alterations in cadherin expression and function. The primary focus of this review is to coalesce recent data on cadherins in neural crest cells, from their specification to their emergence as motile cells soon after EMT, and to highlight the complexities of cadherin expression beyond our current perceptions, including the hypothesis that the neural crest EMT is a transition involving a predominantly singular cadherin switch. Further advancements in genetic approaches and molecular techniques will provide greater opportunities to integrate data from various model systems in order to distinguish unique or overlapping functions of cadherins expressed at any point throughout the ontogeny of the neural crest.

Effects of RET, NRG1 and NRG3 Polymorphisms in a Chinese Population with Hirschsprung Disease

The RET proto-oncogene was identified as a major locus involved in Hirschsprung disease (HSCR). A genome-wide association study (GWAS) and whole exome sequencing identified NRG1 and NRG3 as additional HSCR susceptibility loci. We investigated the effects of RET (rs2506030 and rs2435357), NRG1 (rs2439302, rs16879552 and rs7835688) and NRG3 (rs10748842, rs10883866 and rs6584400) polymorphisms in a Chinese population with HSCR. We assessed single nucleotide polymorphisms (SNPs) in the RET, NRG1 and NRG3 genes in a cohort of 362 sporadic HSCR patients and 1,448 normal controls using a TaqMan genotyping assay. Significant associations were found between HSCR risk and rs2506030, rs2435357, rs2439302 and rs7835688 (odds ratio [OR] 1.64, P = 1.72E-06; 2.97, P = 5.15E-33; 1.84, P = 9.36E-11; and 1.93, P = 1.88E-12, respectively). Two locus analyses of SNPs indicated increased disease risks of HSCR between NRG1 rs2439302 and RET rs2435357 or rs2506030. RET rs2506030 (GG genotype) and rs2435357 (TT genotype), in combination with NRG1 rs2439302 (GG genotype), were strongly associated with the highest risk of HSCR (OR = 56.53, P = 4.50E-07) compared with the two loci or a single SNP of either RET or NRG1. Our results support the association between genetic variation of RET and NRG1 and susceptibility to HSCR in the Chinese population.

Zeb2 Regulates Cell Fate at the Exit from Epiblast State in Mouse Embryonic Stem Cells

In human embryonic stem cells (ESCs) the transcription factor Zeb2 regulates neuroectoderm versus mesendoderm formation, but it is unclear how Zeb2 affects the global transcriptional regulatory network in these cell‐fate decisions. We generated Zeb2 knockout (KO) mouse ESCs, subjected them as embryoid bodies (EBs) to neural and general differentiation and carried out temporal RNA‐sequencing (RNA‐seq) and reduced representation bisulfite sequencing (RRBS) analysis in neural differentiation. This shows that Zeb2 acts preferentially as a transcriptional repressor associated with developmental progression and that Zeb2 KO ESCs can exit from their naïve state. However, most cells in these EBs stall in an early epiblast‐like state and are impaired in both neural and mesendodermal differentiation. Genes involved in pluripotency, epithelial‐to‐mesenchymal transition (EMT), and DNA‐(de)methylation, including Tet1, are deregulated in the absence of Zeb2. The observed elevated Tet1 levels in the mutant cells and the knowledge of previously mapped Tet1‐binding sites correlate with loss‐of‐methylation in neural‐stimulating conditions, however, after the cells initially acquired the correct DNA‐methyl marks. Interestingly, cells from such Zeb2 KO EBs maintain the ability to re‐adapt to 2i + LIF conditions even after prolonged differentiation, while knockdown of Tet1 partially rescues their impaired differentiation. Hence, in addition to its role in EMT, Zeb2 is critical in ESCs for exit from the epiblast state, and links the pluripotency network and DNA‐methylation with irreversible commitment to differentiation. Stem Cells2017;35:611–625

WNT/β-catenin signaling mediates human neural crest induction via a pre-neural border intermediate

Neural crest (NC) cells arise early in vertebrate development, migrate extensively and contribute to a diverse array of ectodermal and mesenchymal derivatives. Previous models of NC formation suggested derivation from neuralized ectoderm, via meso-ectodermal, or neural-non-neural ectoderm interactions. Recent studies using bird and amphibian embryos suggest an earlier origin of NC, independent of neural and mesodermal tissues. Here, we set out to generate a model in which to decipher signaling and tissue interactions involved in human NC induction. Our novel human embryonic stem cell (ESC)-based model yields high proportions of multipotent NC cells (expressing SOX10, PAX7 and TFAP2A) in 5 days. We demonstrate a crucial role for WNT/β-catenin signaling in launching NC development, while blocking placodal and surface ectoderm fates. We provide evidence of the delicate temporal effects of BMP and FGF signaling, and find that NC development is separable from neural and/or mesodermal contributions. We further substantiate the notion of a neural-independent origin of NC through PAX6 expression and knockdown studies. Finally, we identify a novel pre-neural border state characterized by early WNT/β-catenin signaling targets that displays distinct responses to BMP and FGF signaling from the traditional neural border genes. In summary, our work provides a fast and efficient protocol for human NC differentiation under signaling constraints similar to those identified in vivo in model organisms, and strengthens a framework for neural crest ontogeny that is separable from neural and mesodermal fates.

Sip1 regulates the generation of the inner nuclear layer retinal cell lineages in mammals

The transcription factor Sip1 (Zeb2) plays multiple roles during CNS development from early acquisition of neural fate to cortical neurogenesis and gliogenesis. In humans, SIP1 (ZEB2) haploinsufficiency leads to Mowat-Wilson syndrome, a complex congenital anomaly including intellectual disability, epilepsy and Hirschsprung disease. Here we uncover the role of Sip1 in retinogenesis. Somatic deletion of Sip1 from mouse retinal progenitors primarily affects the generation of inner nuclear layer cell types, resulting in complete loss of horizontal cells and reduced numbers of amacrine and bipolar cells, while the number of Muller glia is increased. Molecular analysis places Sip1 downstream of the eye field transcription factor Pax6 and upstream of Ptf1a in the gene network required for generating the horizontal and amacrine lineages. Intriguingly, characterization of differentiation dynamics reveals that Sip1 has a role in promoting the timely differentiation of retinal interneurons, assuring generation of the proper number of the diverse neuronal and glial cell subtypes that constitute the functional retina in mammals.

Mouse models of Hirschsprung disease and other developmental disorders of the enteric nervous system: Old and new players

Hirschsprung disease (HSCR, intestinal aganglionosis) is a multigenic disorder with variable penetrance and severity that has a general population incidence of 1/5000 live births. Studies using animal models have contributed to our understanding of the developmental origins of HSCR and the genetic complexity of this disease. This review summarizes recent progress in understanding control of enteric nervous system (ENS) development through analyses in mouse models. An overview of signaling pathways that have long been known to control the migration, proliferation and differentiation of enteric neural progenitors into and along the developing gut is provided as a framework for the latest information on factors that influence enteric ganglia formation and maintenance. Newly identified genes and additional factors beyond discrete genes that contribute to ENS pathology including regulatory sequences, miRNAs and environmental factors are also introduced. Finally, because HSCR has become a paradigm for complex oligogenic diseases with non-Mendelian inheritance, the importance of gene interactions, modifier genes, and initial studies on genetic background effects are outlined.

A Diagnosis to Consider in Intellectual Disability: Mowat-Wilson Syndrome

Mowat-Wilson syndrome is a multiple congenital anomaly and intellectual disability syndrome characterized by a unique face and various other structural and functional anomalies. The condition is caused by de novo heterozygous mutations or deletions in ZEB2 gene located at 2q22. ZEB2 encodes Sip1 protein, which acts during central nervous system development as an important transcription factor. Herein, we report on 3 novel mutations in 6 patients with the syndrome, with an overview of corresponding clinical findings. Growth retardation and Hirschsprung disease were less common in the present cohort. One patient with a novel mutation p.Y489X had no associated anomalies except the characteristic facial and neurobehavioral phenotype. Reporting new patients with novel mutations would contribute to better delineation of the syndrome and would help clinicians establish formal diagnostic criteria and genotype-phenotype correlations.

A de novo triplication on 2q22.3 including the entire ZEB2 gene associated with global developmental delay, multiple congenital anomalies and behavioral abnormalities

BACKGROUND

Mowat-Wilson syndrome (MWS) is a genetic condition characterized by distinctive facial features, moderate to severe intellectual disability, developmental delay and multiple congenital anomalies. MWS is caused by heterozygous mutations or deletions of the ZEB2 gene located on chromosome 2q22.3. At present, over 190 cases with mutations and deletions involving the ZEB2 gene have been reported, but triplication or duplication of reciprocal region of Mowat-Wilson syndrome has never been reported.

CASE PRESENTATION

Here we report a 2-year-2-month-old boy carrying a de novo 2.9 Mb complex copy number gain at 2q22.3 involving triplication of ZEB2 gene. The boy is characterized by intrauterine growth retardation, hypotonia, cognitive impairment, multiple congenital anomalies and behavioral abnormalities.

CONCLUSION

This case provides evidence that triplication of ZEB2 gene may be clinical significance and ZEB2 gene is likely to be a dosage sensitive gene.

Sleep disturbance in Mowat-Wilson syndrome

Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome caused by a heterozygous mutation or deletion of the ZEB2 gene. It is characterized by a distinctive facial appearance in association with intellectual disability (ID) and variable other features including agenesis of the corpus callosum, seizures, congenital heart defects, microcephaly, short stature, hypotonia, and Hirschsprung disease. The current study investigated sleep disturbance in people with MWS. In a series of unstructured interviews focused on development and behaviors in MWS, family members frequently reported sleep disturbance, particularly early-morning waking and frequent night waking. The Sleep Disturbance Scale for Children (SDSC) was therefore administered to a sample of 35 individuals with MWS, along with the Developmental Behaviour Checklist (DBC) to measure behavioral and emotional disturbance. A high level of sleep disturbance was found in the MWS sample, with 53% scoring in the borderline range and 44% in the clinical disorder range for at least one subscale of the SDSC. Scores were highest for the Sleep-wake transition disorders subscale, with 91% of participants reaching at least the borderline disorder range. A significant positive association was found between total scores on the SDSC and the DBC Total Behaviour Problem Score. These results suggest that sleep disorders should be screened for in people with MWS, and where appropriate, referrals to sleep specialists made for management of sleep problems.

Knockout mouse models of Hirschsprung's disease

PURPOSE

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system, which occurs due to the failure of neural crest cell migration. Rodent animal models of aganglionosis have contributed greatly to our understanding of the genetic basis of HSCR. Several natural or target mutations in specific genes have been reported to produce developmental defects in neural crest migration, differentiation or survival. The aim of this study was to review the currently available knockout models of HSCR to better understand the molecular basis of HSCR.

METHODS

A review of the literature using the keywords "Hirschsprung's disease", "aganglionosis", "megacolon" and "knockout mice model" was performed. Resulting publications were reviewed for relevant mouse models of human aganglionosis. Reference lists were screened for additional relevant studies.

RESULTS

16 gene knockout mouse models were identified as relevant rodent models of human HSCR. Due to the deletion of a specific gene, the phenotypes of these knockout models are diverse and range from small bowel dilatation and muscular hypertrophy to total intestinal aganglionosis.

CONCLUSIONS

Mouse models of aganglionosis have been instrumental in the discovery of the causative genes of HSCR. Although important advances have been made in understanding the genetic basis of HSCR, animal models of aganglionosis in future should further help to identify the unknown susceptibility genes in HSCR.

De novo inbred heterozygous Zeb2/Sip1 mutant mice uniquely generated by germ-line conditional knockout exhibit craniofacial, callosal and behavioral defects associated with Mowat-Wilson syndrome

Mowat-Wilson syndrome (MOWS) is caused by de novo heterozygous mutation at ZEB2 (SIP1, ZFHX1B) gene, and exhibit moderate to severe intellectual disability (ID), a characteristic facial appearance, epilepsy and other congenital anomalies. Establishing a murine MOWS model is important, not only for investigating the pathogenesis of this disease, but also for identifying compounds that may improve the symptoms. However, because the heterozygous Zeb2 knockout mouse could not be maintained as a mouse line with the inbred C57BL/6 background, it was difficult to use those mice for the study of MOWS. Here, we systematically generated de novo Zeb2 Δex7/+ mice by inducing the Zeb2 mutation in the germ cells using conditional recombination system. The de novo Zeb2 Δex7/+ mice with C57BL/6 background developed multiple defects relevant to MOWS, including craniofacial abnormalities, defective corpus callosum formation and the decreased number of parvalbumin interneurons in the cortex. In behavioral analyses, these mice showed reduced motor activity, increased anxiety and impaired sociability. Notably, during the Barnes maze test, immobile Zeb2 mutant mice were observed over repeated trials. In contrast, neither the mouse line nor the de novo Zeb2 Δex7/+ mice with the closed colony ICR background showed cranial abnormalities or reduced motor activities. These results demonstrate the advantages of using de novo Zeb2 Δex7/+ mice with the C57BL/6 background as the MOWS model. To our knowledge, this is the first time an inducible de novo mutation system has been applied to murine germline cells to produce an animal model of a human congenital disease.

Zeb2: A multifunctional regulator of nervous system development

Zinc finger E-box binding homeobox (Zeb) 2 is a transcription factor, identified due its ability to bind Smad proteins, and consists of multiple functional domains which interact with a variety of transcriptional co-effectors. The complex nature of the Zeb2, both at its genetic and protein levels, underlie its multifunctional properties, with Zeb2 capable of acting individually or as part of a transcriptional complex to repress, and occasionally activate, target gene expression. This review introduces Zeb2 as an essential regulator of nervous system development. Zeb2 is expressed in the nervous system throughout its development, indicating its importance in neurogenic and gliogenic processes. Indeed, mutation of Zeb2 has dramatic neurological consequences both in animal models, and in humans with Mowat-Wilson syndrome, which results from heterozygous ZEB2 mutations. The mechanisms by which Zeb2 regulates the induction of the neuroectoderm (CNS primordium) and the neural crest (PNS primordium) are reviewed herein. We then describe how Zeb2 acts to direct the formation, delamination, migration and specification of neural crest cells. Zeb2 regulation of the development of a number of cerebral regions, including the neocortex and hippocampus, are then described. The diverse molecular mechanisms mediating Zeb2-directed development of various neuronal and glial populations are reviewed. The role of Zeb2 in spinal cord and enteric nervous system development is outlined, while its essential function in CNS myelination is also described. Finally, this review discusses how the neurodevelopmental defects of Zeb2 mutant mice delineate the developmental dysfunctions underpinning the multiple neurological defects observed in Mowat-Wilson syndrome patients.

Common prefrontal cortical gene expression profiles between adolescent SHR/NCrl and WKY/NCrl rats which showed inattention behavior

Factor analyses of attention-deficit/hyperactivity (ADHD) symptoms divide the behavioral symptoms of ADHD into two separate domains, one reflecting inattention and the other, a combination of hyperactivity and impulsivity. Identifying domain-specific genetic risk variants may aid in the discovery of specific biological risk factors for ADHD. In contrast with data available on genes involved in hyperactivity and impulsivity, there is limited information on the genetic influences of inattention. Transcriptional profiling analysis in animal models of disorders may provide an important tool to identify genetic involvement in behavioral phenotypes. To explore some of the potential genetic underpinnings of ADHD inattention, we examined common differentially expressed genes (DEGs) in the prefrontal cortex of SHR/NCrl, the most validated animal model of ADHD and WKY/NCrl, animal model of ADHD-inattentive type. In contrast with Wistar rats, strain representing the "normal" heterogeneous population, SHR/NCrl and WKY/NCrl showed inattention behavior in the Y-maze task. The common DEGs in the PFC of SHR/NCrl and WKY/NCrl vs. Wistar rats are those involved in transcription (e.g. Creg1, Thrsp, Zeb2), synaptic transmission (e.g. Atp2b2, Syt12, Chrna5), neurological system process (e.g. Atg7, Cacnb4, Grin3a), and immune response (e.g. Atg7, Ip6k2, Mx2). qRT-PCR analyses validated expression patterns of genes representing the major functional gene families among the DEGs (Grin3a, Thrsp, Vof-16 and Zeb2). Although further studies are warranted, the present findings indicate novel genes associated with known functional pathways of relevance to ADHD which are assumed to play important roles in the etiology of ADHD-inattentive subtype.

ZEB2 gene mutation and duplication of 22q11.23 in Mowat-Wilson syndrome

Mowat-Wilson syndrome is a recently delineated multiple congenital anomaly syndrome characterized by a distinctive facial appearance in association with intellectual disability, microcephaly, agenesis of the corpus callosum, seizures, congenital heart disease, Hirschsprung disease, short stature, and genitourinary anomalies. We report a 2-year-10-month-old white female with this syndrome caused by mutations in the ZEB2 gene, and in addition a duplication of the 22q11.23, a previously undocumented occurrence.

Mowat-Wilson syndrome: neurological and molecular study in seven patients

OBJECTIVE

To present a seven-cases serie of Mowat-Wilson syndrome (MWS).

METHOD

All patients with positive mutation for the ZEB2 were evaluated by a geneticist and a neurologist, with clinical and laboratorial characterization.

RESULTS

A peculiar facies and mental retardation were present in all patients. The Denver II scale showed intense delay in all aspects, especially fine motor and adaptive. Acquired microcephaly was observed in five patients. Only one patient did not present epilepsy. Epilepsy was focal and predominating in sleep, with status epilepticus in three patients. The initial seizure was associated with fever in most patients (4/6). The EEG showed epileptic focal activity (5/7). The imaging studies revealed total agenesis (4/7) and partial agenesis of the corpus callosum (1/7).

CONCLUSION

Physicians who care for patients with mental retardation and epilepsy should be aware of SMW.

Regulation of C. elegans neuronal differentiation by the ZEB-family factor ZAG-1 and the NK-2 homeodomain factor CEH-28

The C. elegans pharyngeal neuron M4 is a multi-functional cell that acts as a cholinergic motor neuron to stimulate peristaltic pharyngeal muscle contraction and as a neuroendocrine cell secreting neuropeptides and growth factors to affect other cells both inside and outside the pharynx. The conserved transcription factors ZAG-1 and CEH-28 are co-expressed in M4 through most of development, and here we examine how these factors contribute to M4 differentiation. We find ZAG-1 functions upstream of CEH-28 in a branched pathway to activate expression of different sets of M4 differentiation markers. CEH-28 activates expression of the growth factor genes dbl-1 and egl-17, and the neuropeptide genes flp-5 and flp-2, while ZAG-1 activates expression of the serotonin receptor ser-7, as well as expression of ceh-28 and its downstream targets. Other markers of M4 differentiation are expressed normally in both zag-1 and ceh-28 mutants, including the neuropeptide gene flp-21 and the acetylcholine biosynthetic gene unc-17. Unlike ceh-28 mutants, zag-1 mutants completely lack peristaltic muscle contractions resulting from broader defects in M4 differentiation. Despite these defects, neither ZAG-1 nor CEH-28 are terminal selectors of the M4 phenotype, and we suggest they function in a hierarchy to regulate different aspects of M4 differentiation.

Mowat-Wilson syndrome: deafness in the first Egyptian case who was conceived by intracytoplasmic sperm injection

Mowat-Wilson syndrome is a genetic disease caused by heterozygous mutations or deletions of the zinc finger E-box-binding homeobox 2 (ZEB2) gene. The syndrome is characterized by typical facial features, moderate-to-severe mental retardation, epilepsy and variable congenital malformations, including Hirschsprung disease, genital anomalies, congenital heart disease, agenesis of the corpus callosum, and eye defects. The prevalence of Mowat-Wilson syndrome is currently unknown, but it seems that Mowat-Wilson syndrome is underdiagnosed, particularly in patients without Hirschsprung disease. We report here the first Egyptian case of Mowat-Wilson syndrome who was conceived by intracytoplasmic sperm injection. The patient manifested bilateral sensorineural hearing loss--a new feature not previously reported in cases of Mowat-Wilson syndrome. This report describes the first Egyptian patient of Mowat-Wilson syndrome who was conceived after intracytoplasmic sperm injection, and provides a new evidence for the inclusion of deafness among the congenital defects of the syndrome.

Tumors of the neural crest: Common themes in development and cancer

The neural crest (NC) is a remarkable transient structure in the vertebrate embryo that gives rise to a highly versatile population of pluripotent cells that contribute to the formation of multiple tissues and organs throughout the body. In order to achieve their task, NC-derived cells have developed specialized mechanisms to promote (1) their transition from an epithelial to a mesenchymal phenotype, (2) their capacity for extensive migration and cell proliferation, and (3) their ability to produce diverse cell types largely depending on the microenvironment encountered during and after their migratory path. Following embryogenesis, these same features of cellular motility, invasion, and proliferation can become a liability by contributing to tumorigenesis and metastasis. Ample evidence has shown that cancer cells have cleverly co-opted many of the genetic and molecular features used by developing NC cells. This review focuses on tumors that arise from NC-derived tissues and examines mechanistic themes shared during their oncogenic and metastatic development with embryonic NC cell ontogeny.

De novo interstitial deletion 2q14.1q22.1: is there a recognizable phenotype?

In this report we describe a male patient with a rare de novo interstitial deletion of chromosome 2q14.1-q22.1. His karyotype was reported as 46,XY,del(2)(q13q21) but subsequent array comparative genomic hybridization (array CGH) analysis redefined the deletion breakpoints as 2q14.1 and 2q22.1. Eight patients have been reported with deletions either within or spanning the region 2q13 or 2q14 to 2q22.1. In five patients the diagnosis was made by karyotype analysis alone and in three reported patients and the proband array CGH analysis was also performed. When the proband was compared with the eight previously reported patients it was apparent that they shared many clinical findings suggesting that patients with a de novo interstitial deletion involving 2q13 or 2q14 to 2q21 or 2q22 may have a recognizable phenotype. There are 14 known disease-associated genes in the deleted region of 2q14.1-q22.1 and their possible phenotypic effects on the proband and the eight previously reported patients are discussed.

CHARGE-like presentation, craniosynostosis and mild Mowat-Wilson Syndrome diagnosed by recognition of the distinctive facial gestalt in a cohort of 28 new cases

Mowat-Wilson syndrome (MWS) is characterized by moderate to severe intellectual disability and distinctive facial features in association with variable structural congenital anomalies/clinical features including congenital heart disease, Hirschsprung disease, hypospadias, agenesis of the corpus callosum, short stature, epilepsy, and microcephaly. Less common clinical features include ocular anomalies, craniosynostosis, mild intellectual disability, and choanal atresia. These cases may be more difficult to diagnose. In this report, we add 28 MWS patients with molecular confirmation of ZEB2 mutation, including seven with an uncommon presenting feature. Among the "unusual" patients, two patients had clinical features of charge syndrome including choanal atresia, coloboma, cardiac defects, genitourinary anomaly (1/2), and severe intellectual disability; two patients had craniosynostosis; and three patients had mild intellectual disability. Sixteen patients have previously-unreported mutations in ZEB2. Genotype-phenotype correlations were suggested in those with mild intellectual disability (two had a novel missense mutation in ZEB2, one with novel splice site mutation). This report increases the number of reported patients with MWS with unusual features, and is the first report of MWS in children previously thought to have CHARGE syndrome. These patients highlight the importance of facial gestalt in the accurate identification of MWS when less common features are present.

Oncogenic roles of EMT-inducing transcription factors

The plasticity of cancer cells underlies their capacity to adapt to the selective pressures they encounter during tumour development. Aberrant reactivation of epithelial-mesenchymal transition (EMT), an essential embryonic process, can promote cancer cell plasticity and fuel both tumour initiation and metastatic spread. Here we discuss the roles of EMT-inducing transcription factors in creating a pro-tumorigenic setting characterized by an intrinsic ability to withstand oncogenic insults through the mitigation of p53-dependent oncosuppressive functions and the gain of stemness-related properties.

The spectrum of ZEB2 mutations causing the Mowat-Wilson syndrome in Japanese populations

Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by moderate or severe intellectual disability, a characteristic facial appearance, microcephaly, epilepsy, agenesis or hypoplasia of the corpus callosum, congenital heart defects, Hirschsprung disease, and urogenital/renal anomalies. It is caused by de novo heterozygous loss of function mutations including nonsense mutations, frameshift mutations, and deletions in ZEB2 at 2q22. ZEB2 encodes the zinc finger E-box binding homeobox 2 protein consisting of 1,214 amino acids. Herein, we report 13 nonsense and 27 frameshift mutations from 40 newly identified MWS patients in Japan. Although the clinical findings of all the Japanese MWS patients with nonsense and frameshift mutations were quite similar to the previous review reports of MWS caused by nonsense mutations, frameshift mutations and deletions of ZEB2, the frequencies of microcephaly, Hirschsprung disease, and urogenital/renal anomalies were small. Patients harbored mutations spanning the region between the amino acids 55 and 1,204 in wild-type ZEB2. There was no obvious genotype-phenotype correlation among the patients. A transfection study demonstrated that the cellular level of the longest form of the mutant ZEB2 protein harboring the p.D1204Rfs*29 mutation was remarkably low. The results showed that the 3'-end frameshift mutation of ZEB2 causes MWS due to ZEB2 instability.

SIP1 expression patterns in brain investigated by generating a SIP1-EGFP reporter knock-in mouse

A loss of function of SIP1 (Smad interacting protein 1) in the mouse as well as in human of Mowat-Wilson syndrome results in severe and multiple defects in neural tissue development, especially in the brain. However, no detailed expression analysis of SIP1 during brain development has been previously reported. In this study, we describe the generation of an EGFP knock-in reporter mouse for the Sip1 locus and our subsequent analysis of SIP1-EGFP fusion protein expression during brain development. SIP1-EGFP expression was observed in the pyramidal neurons of the hippocampus, the dentate gyrus, and the postmitotic neurons in the cerebral cortex. In layer 5 of the cerebral cortex, SIP1-EGFP expression was complementary to the Ctip2-expressing neurons, most of which are thought to be the cortico-spinal neurons. This suggested that SIP1-EGFP expressing cells might have the specific trajectory targets other than the spinal region. We further observed SIP1-EGFP expression in oligodendrocytes of the corpus callosum and fimbria, Bergmann glial cells of the cerebellum, the olfactory bulb, and in the serotonergic and dopaminergic neurons of the raphe nuclei in the brainstem. These findings may help to clarify the unknown roles of SIP1 in these cells and the pathoetiology of Mowat-Wilson syndrome.

Sip1 mediates an E-cadherin-to-N-cadherin switch during cranial neural crest EMT

Sip1 promotes the mesenchymalization stage of the neural crest epithelial-to-mesenchymal transition by inducing a transcriptional switch in cells from expression of E-cadherin to N-cadherin.

The neural crest, an embryonic stem cell population, initially resides within the dorsal neural tube but subsequently undergoes an epithelial-to-mesenchymal transition (EMT) to commence migration. Although neural crest and cancer EMTs are morphologically similar, little is known regarding conservation of their underlying molecular mechanisms. We report that Sip1, which is involved in cancer EMT, plays a critical role in promoting the neural crest cell transition to a mesenchymal state. Sip1 transcripts are expressed in premigratory/migrating crest cells. After Sip1 loss, the neural crest specifier gene FoxD3 was abnormally retained in the dorsal neuroepithelium, whereas Sox10, which is normally required for emigration, was diminished. Subsequently, clumps of adherent neural crest cells remained adjacent to the neural tube and aberrantly expressed E-cadherin while lacking N-cadherin. These findings demonstrate two distinct phases of neural crest EMT, detachment and mesenchymalization, with the latter involving a novel requirement for Sip1 in regulation of cadherin expression during completion of neural crest EMT.

Four amino acids within a tandem QxVx repeat in a predicted extended α-helix of the Smad-binding domain of Sip1 are necessary for binding to activated Smad proteins

The zinc finger transcription factor Smad-interacting protein-1 (Sip1; Zeb2, Zfhx1b) plays an important role during vertebrate embryogenesis in various tissues and differentiating cell types, and during tumorigenesis. Previous biochemical analysis suggests that interactions with several partner proteins, including TGFβ family receptor-activated Smads, regulate the activities of Sip1 in the nucleus both as a DNA-binding transcriptional repressor and activator. Using a peptide aptamer approach we mapped in Sip1 its Smad-binding domain (SBD), initially defined as a segment of 51 amino acids, to a shorter stretch of 14 amino acids within this SBD. Modelling suggests that this short SBD stretch is part of an extended α-helix that may fit the binding to a hydrophobic corridor within the MH2 domain of activated Smads. Four amino acids (two polar Q residues and two non-polar V residues) that form the tandem repeat (QxVx)₂ in this 14-residue stretch were found to be crucial for binding to both TGFβ/Nodal/Activin-Smads and BMP-Smads. A full-length Sip1 with collective mutation of these Q and V residues (to A) no longer binds to Smads, while it retains its binding activity to its cognate bipartite target DNA sequence. This missense mutant Sip1(AxAx)₂ provides a new molecular tool to identify SBD (in)dependent target genes in Sip1-controlled TGFβ and/or BMP (de)regulated cellular, developmental and pathological processes.

BMP-Smad 1/5/8 signalling in the development of the nervous system

The transcription factors, Smad1, Smad5 and Smad8, are the pivotal intracellular effectors of the bone morphogenetic protein (BMP) family of proteins. BMPs and their receptors are expressed in the nervous system (NS) throughout its development. This review focuses on the actions of Smad 1/5/8 in the developing NS. The mechanisms by which these Smad proteins regulate the induction of the neuroectoderm, the central nervous system (CNS) primordium, and finally the neural crest, which gives rise to the peripheral nervous system (PNS), are reviewed herein. We describe how, following neural tube closure, the most dorsal aspect of the tube becomes a signalling centre for BMPs, which directs the pattern of the development of the dorsal spinal cord (SC), through the action of Smad1, Smad5 and Smad8. The direct effects of Smad 1/5/8 signalling on the development of neuronal and non-neuronal cells from various neural progenitor cell populations are then described. Finally, this review discusses the neurodevelopmental abnormalities associated with the knockdown of Smad 1/5/8.

Smad-interacting protein 1 affects acute and tonic, but not chronic pain

BACKGROUND

Smad-interacting protein 1 (also named Zeb2 and Zfhx1b) is a transcription factor that plays an important role in neuronal development and, when mutated, causes Mowat-Wilson syndrome (MWS). A corresponding mouse model carrying a heterozygous Zeb2 deletion was comprehensively analysed in the German Mouse Clinic. The most prominent phenotype was the reduced pain sensitivity. In this study, we investigated the role of Zeb2 in inflammatory and neuropathic pain.

METHODS

For this, we tested mutant Zeb2 animals in different models of inflammatory pain like abdominal constriction, formalin and carrageenan test. Furthermore, we studied the pain reactivity of the mice after peripheral nerve ligation. To examine the nociceptive transmission of primary sensory dorsal root ganglia (DRG) neurons, we determined the neuronal activity in the spinal dorsal horn after the formalin test using staining of c-Fos. Next, we characterized the neuronal cell population in the DRGs and in the sciatic nerve to study the effect of the Zeb2 mutation on peripheral nerve morphology.

RESULTS

The present data show that Zeb2 is involved in the development of primary sensory DRG neurons, especially of C- and Aδ fibres. These alterations contribute to a hypoalgesic phenotype in inflammatory but not in neuropathic pain in these Zeb2(+/-) mice.

CONCLUSION

Our data suggest that the under-reaction to pain observed in MWS patients results from a reduced responsivity to nociceptive stimulation rather than an inability to communicate discomfort.

Enteric nervous system development: migration, differentiation, and disease

The enteric nervous system (ENS) provides the intrinsic innervation of the bowel and is the most neurochemically diverse branch of the peripheral nervous system, consisting of two layers of ganglia and fibers encircling the gastrointestinal tract. The ENS is vital for life and is capable of autonomous regulation of motility and secretion. Developmental studies in model organisms and genetic studies of the most common congenital disease of the ENS, Hirschsprung disease, have provided a detailed understanding of ENS development. The ENS originates in the neural crest, mostly from the vagal levels of the neuraxis, which invades, proliferates, and migrates within the intestinal wall until the entire bowel is colonized with enteric neural crest-derived cells (ENCDCs). After initial migration, the ENS develops further by responding to guidance factors and morphogens that pattern the bowel concentrically, differentiating into glia and neuronal subtypes and wiring together to form a functional nervous system. Molecules controlling this process, including glial cell line-derived neurotrophic factor and its receptor RET, endothelin (ET)-3 and its receptor endothelin receptor type B, and transcription factors such as SOX10 and PHOX2B, are required for ENS development in humans. Important areas of active investigation include mechanisms that guide ENCDC migration, the role and signals downstream of endothelin receptor type B, and control of differentiation, neurochemical coding, and axonal targeting. Recent work also focuses on disease treatment by exploring the natural role of ENS stem cells and investigating potential therapeutic uses. Disease prevention may also be possible by modifying the fetal microenvironment to reduce the penetrance of Hirschsprung disease-causing mutations.

Contribution of rare and common variants determine complex diseases-Hirschsprung disease as a model

Finding genes for complex diseases has been the goal of many genetic studies. Most of these studies have been successful by searching for genes and mutations in rare familial cases, by screening candidate genes and by performing genome wide association studies. However, only a small fraction of the total genetic risk for these complex genetic diseases can be explained by the identified mutations and associated genetic loci. In this review we focus on Hirschsprung disease (HSCR) as an example of a complex genetic disorder. We describe the genes identified in this congenital malformation and postulate that both common 'low penetrant' variants in combination with rare or private 'high penetrant' variants determine the risk on HSCR, and likely, on other complex diseases. We also discuss how new technological advances can be used to gain further insights in the genetic background of complex diseases. Finally, we outline a few steps to develop functional assays in order to determine the involvement of these variants in disease development.

Multilayer control of the EMT master regulators

Metastasis is the leading cause of cancer-associated death in most tumor types. Metastatic dissemination of cancer cells from the primary tumor is believed to be initiated by the reactivation of an embryonic development program referred to as epithelial-mesenchymal transition (EMT), whereby epithelial cells lose apicobasal polarity and cell-cell contacts, and gain mesenchymal phenotypes with increased migratory and invasive capabilities. EMT has also been implicated in the regulation of cancer stem cell property, immune suppression and cancer regression. Several transcription factors have been identified as master regulators of EMT, including the Snail, Zeb and Twist families, and their expression is tightly regulated at different steps of transcription, translation and protein stability control by a variety of cell-intrinsic pathways as well as extracellular cues. Here, we review the recent literature on the signaling pathways and mechanisms that control the expression of these master transcription factors during EMT and cancer progression.

Riding the crest of the wave: parallels between the neural crest and cancer in epithelial-to-mesenchymal transition and migration

The neural crest (NC) is first induced as an epithelial population of cells at the neural plate border requiring complex signaling between bone morphogenetic protein, Wnt, and fibroblast growth factors to differentiate the neural and NC fate from the epidermis. Remarkably, following induction, these cells undergo an epithelial-to-mesenchymal transition (EMT), delaminate from the neural tube, and migrate through various tissue types and microenvironments before reaching their final destination where they undergo terminal differentiation. This process is mirrored in cancer metastasis, where a primary tumor will undergo an EMT before migrating and invading other cell populations to create a secondary tumor site. In recent years, as our understanding of NC EMT and migration has deepened, important new insights into tumorigenesis and metastasis have also been achieved. These discoveries have been driven by the observation that many cancers misregulate developmental genes to reacquire proliferative and migratory states. In this review, we examine how the NC provides an excellent model for studying EMT and migration. These data are discussed from the perspective of the gene regulatory networks that control both NC and cancer cell EMT and migration. Deciphering these processes in a comparative manner will expand our knowledge of the underlying etiology and pathogenesis of cancer and promote the development of novel targeted therapeutic strategies for cancer patients. © 2013 Wiley Periodicals, Inc.

Aptamers and their potential to selectively target aspects of EGF, Wnt/β-catenin and TGFβ-smad family signaling

The smooth identification and low-cost production of highly specific agents that interfere with signaling cascades by targeting an active domain in surface receptors, cytoplasmic and nuclear effector proteins, remain important challenges in biomedical research. We propose that peptide aptamers can provide a very useful and new alternative for interfering with protein–protein interactions in intracellular signal transduction cascades, including those emanating from activated receptors for growth factors. By their targeting of short, linear motif type of interactions, peptide aptamers have joined nucleic acid aptamers for use in signaling studies because of their ease of production, their stability, their high specificity and affinity for individual target proteins, and their use in high-throughput screening protocols. Furthermore, they are entering clinical trials for treatment of several complex, pathological conditions. Here, we present a brief survey of the use of aptamers in signaling pathways, in particular of polypeptide growth factors, starting with the published as well as potential applications of aptamers targeting Epidermal Growth Factor Receptor signaling. We then discuss the opportunities for using aptamers in other complex pathways, including Wnt/β-catenin, and focus on Transforming Growth Factor-β/Smad family signaling.

Mowat-Wilson syndrome in a fetus with antenatal diagnosis of short corpus callosum: advocacy for standard autopsy

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene rarely diagnosed prenatally and with little fetal description reported. It is mainly characterized by moderate-to-severe intellectual disability, epilepsy, facial dysmorphism and various malformations including Hirschsprung disease and corpus callosum anomalies. Here we report a fetal case of MWS well described, suspected at standard autopsy. The association of a corpus callosum hypoplasia with a histological Hirschsprung disease and a typical facial gestalt allowed the guiding of genetic testing. Classical fetopathological examination still keeps indications in cases of syndromic association in the era of virtual autopsy.

Epilepsy in Mowat-Wilson syndrome: delineation of the electroclinical phenotype

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene and is characterized by distinctive facial features, epilepsy, moderate to severe intellectual disability, corpus callosum abnormalities and other congenital malformations. Epilepsy is considered a main manifestation of the syndrome, with a prevalence of about 70-75%. In order to delineate the electroclinical phenotype of epilepsy in MWS, we investigated epilepsy onset and evolution, including seizure types, EEG features, and response to anti-epileptic therapies in 22 patients with genetically confirmed MWS. Onset of seizures occurred at a median age of 14.5 months (range: 1-108 months). The main seizure types were focal and atypical absence seizures. In all patients the first seizure was a focal seizure, often precipitated by fever. The semiology was variable, including hypomotor, versive, or focal clonic manifestations; frequency ranged from daily to sporadic. Focal seizures were more frequent during drowsiness and sleep. In 13 patients, atypical absence seizures appeared later in the course of the disease, usually after the age of 4 years. Epilepsy was usually quite difficult to treat: seizure freedom was achieved in nine out of the 20 treated patients. At epilepsy onset, the EEGs were normal or showed only mild slowing of background activity. During follow-up, irregular, diffuse frontally dominant and occasionally asymmetric spike and waves discharges were seen in most patients. Sleep markedly activated these abnormalities, resulting in continuous or near-to-continuous spike and wave activity during slow wave sleep. Slowing of background activity and poverty of physiological sleep features were seen in most patients. Our data suggest that a distinct electroclinical phenotype, characterized by focal and atypical absence seizures, often preceded by febrile seizures, and age-dependent EEG changes, can be recognized in most patients with MWS.

Exome sequencing identified NRG3 as a novel susceptible gene of Hirschsprung's disease in a Chinese population

Hirschsprung's disease (HSCR) is a complex developmental defect characterized by the absence of enteric ganglia in the gastrointestinal tract. Although the genetic defect of enteric nervous system (ENS) was identified to play a critical role in the progress of HSCR, the systemic genetic dissection of HSCR still needs to be clarified. In this study, we firstly performed exome sequencing of two HSCR patients from a Han Chinese family, including the affected mother and son. After the initial quality filtering (coverage  ≥ 5X and SNP quality score ≥ 40) of the raw data, we identified 13,948 and 13,856 single nucleotide variants (SNVs), respectively. We subsequently compared the SNVs against public databases (dbSNP130, HapMap, and 1000 Genome Project) and obtained a total of 15 novel nonsynonymous SNVs in 15 genes, which were shared between these two patients. Follow-up Sanger sequencing and bioinformatics analysis highlighted variant c.853G>A (p.E285K) in NRG3, a gene involved in the development of ENS. In the validation phase, we sequenced all nine exons of NRG3 in 96 additional sporadic HSCR cases and 110 healthy individuals and identified another nonsynonymous variant c.1329G>A (p.M443I) and two synonymous variants c.828G>A (p.T276T) and c.1365T>A (p.P455P) only in the cases. Our results indicated that NRG3 may be a susceptibility gene for HSCR in a Chinese population.

Development and developmental disorders of the enteric nervous system

The enteric nervous system (ENS) arises from neural crest-derived cells that migrate into and along the gut, leading to the formation of a complex network of neurons and glial cells that regulates motility, secretion and blood flow. This Review summarizes the progress made in the past 5 years in our understanding of ENS development, including the migratory pathways of neural crest-derived cells as they colonize the gut. The importance of interactions between neural crest-derived cells, between signalling pathways and between developmental processes (such as proliferation and migration) in ensuring the correct development of the ENS is also presented. The signalling pathways involved in ENS development that were determined using animal models are also described, as is the evidence for the involvement of the genes encoding these molecules in Hirschsprung disease-the best characterized paediatric enteric neuropathy. Finally, the aetiology and treatment of Hirschsprung disease in the clinic and the potential involvement of defects in ENS development in other paediatric motility disorders are outlined.

Mowat-Wilson syndrome: the first clinical and molecular report of an indonesian patient

Mowat-Wilson syndrome (OMIM 235730) is a genetic condition characterized by moderate-to-severe intellectual disability, a recognizable facial phenotype, and multiple congenital anomalies. The striking facial phenotype in addition to other features such as severely impaired speech, hypotonia, microcephaly, short stature, seizures, corpus callosum agenesis, congenital heart defects, hypospadias, and Hirschsprung disease are particularly important clues for the initial clinical diagnosis. All molecularly confirmed cases with typical MWS have a heterozygous loss-of-function mutation in the zinc finger E-box protein 2 (ZEB2) gene, also called SIP1 (Smad-interacting protein 1) and ZFHX1B, suggesting that haploinsufficiency is the main pathological mechanism. Approximately 80% of mutations are nonsense and frameshift mutations (small insertions or deletions). About half of these mutations are located in exon eight. Here, we report the first Indonesian patient with Mowat-Wilson syndrome confirmed by molecular analysis.

Building a brain in the gut: development of the enteric nervous system

The enteric nervous system (ENS), the intrinsic innervation of the gastrointestinal tract, is an essential component of the gut neuromusculature and controls many aspects of gut function, including coordinated muscular peristalsis. The ENS is entirely derived from neural crest cells (NCC) which undergo a number of key processes, including extensive migration into and along the gut, proliferation, and differentiation into enteric neurons and glia, during embryogenesis and fetal life. These mechanisms are under the molecular control of numerous signaling pathways, transcription factors, neurotrophic factors and extracellular matrix components. Failure in these processes and consequent abnormal ENS development can result in so-called enteric neuropathies, arguably the best characterized of which is the congenital disorder Hirschsprung disease (HSCR), or aganglionic megacolon. This review focuses on the molecular and genetic factors regulating ENS development from NCC, the clinical genetics of HSCR and its associated syndromes, and recent advances aimed at improving our understanding and treatment of enteric neuropathies.

Chromosomal and related Mendelian syndromes associated with Hirschsprung's disease

Hirschsprung's disease (HSCR) is a fairly frequent cause of intestinal obstruction in children. It is characterized as a sex-linked heterogonous disorder with variable severity and incomplete penetrance giving rise to a variable pattern of inheritance. Although Hirschsprung's disease occurs as an isolated phenotype in at least 70% of cases, it is not infrequently associated with a number of congenital abnormalities and associated syndromes, demonstrating a spectrum of congenital anomalies. Certain of these syndromic phenotypes have been linked to distinct genetic sites, indicating underlying genetic associations of the disease and probable gene-gene interaction, in its pathogenesis. These associations with HSCR include Down's syndrome and other chromosomal anomalies, Waardenburg syndrome and other Dominant sensorineural deafness, the Congenital Central Hypoventilation and Mowat-Wilson and other brain-related syndromes, as well as the MEN2 and other tumour associations. A number of other autosomal recessive syndromes include the Shah-Waardenburg, the Bardet-Biedl and Cartilage-hair hypoplasia, Goldberg-Shprintzen syndromes and other syndromes related to cholesterol and fat metabolism among others. The genetics of Hirschsprung's disease are highly complex with the majority of known genetic sites relating to the main susceptibility pathways (RET an EDNRB). Non-syndromic non-familial, short-segment HSCR appears to represent a non-Mendelian condition with variable expression and sex-dependent penetrance. Syndromic and familial forms, on the other hand, have complex patterns of inheritance and being reported as autosomal dominant, recessive and polygenic patterns of inheritance. The phenotypic variability and incomplete penetrance observed in Hirschsprung's disease could also be explained by the involvement of modifier genes, especially in its syndromic forms. In this review, we look at the chromosomal and Mendelian associations and their underlying signalling pathways, to obtain a better understanding of the pathogenetic mechanisms involved in developing aganglionosis of the distal bowel.

Pleiotropic effects of the bone morphogenetic proteins on development of the enteric nervous system

Formation of the enteric nervous system (ENS) from migratory neural crest-derived cells that colonize the primordial gut involves a complex interplay among different signaling molecules. The bone morphogenetic proteins (BMPs), specifically BMP2 and BMP4, play a particularly important role in virtually every stage of gut and ENS development. BMP signaling helps to pattern both the anterior-posterior axis and the radial axis of the gut prior to colonization by migratory crest progenitor cells. BMP signaling then helps regulate the migration of enteric neural crest-derived precursors as they colonize the fetal gut and form ganglia. BMP2 and -4 promote differentiation of enteric neurons in early fetal ENS development and glia at later stages. A major role for BMP signaling in the ENS is regulation of responses to other growth factors. Thus BMP signaling first regulates neurogenesis by modulating responses to GDNF and later gliogenesis through its effects on GGF-2 responses. Furthermore, BMPs promote growth factor dependency for survival of ENS neurons (on NT-3) and glia (on GGF-2) by inducing TrkC (neurons) and ErbB3 (glia). BMP signaling limits total neuron numbers, favoring the differentiation of later born neuronal phenotypes at the expense of earlier born ones thus influencing the neuronal composition of the ENS and the glia/neuron ratio. BMP2 and -4 also promote gangliogenesis via modification of neural cell adhesion molecules and promote differentiation of the circular and then longitudinal smooth muscles. Disruption of BMP signaling leads to defects in the gut and in ENS function commensurate with these complex developmental roles.

Advances in molecular genetics of Hirschsprung's disease

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system, which occurs due to the failure of neural crest cells to fully colonize the gut during embryonic development. It is characterized by the absence of the enteric ganglia in a variable length of the intestine. Substantial progress has been made in understanding the genetic basis of HSCR with the help of advanced genetic analysis techniques and animal models. More than 11 genes have been found to be involved in the pathogenesis of HSCR. The RET gene is the most important susceptibility gene involved in HSCR with both coding and non- coding sequence mutations. Due to phenotypic diversity and genetic complexity observed in HSCR, mutational analysis has limited practical value in genetic counseling and clinical practice. In this review, we discuss the progress that has been made in understanding the molecular genetics of HSCR and summarize the currently identified genes as well as interactions between pathways and gene-modifying loci in HSCR.

Hirschsprung disease: a developmental disorder of the enteric nervous system

Hirschsprung disease (HSCR), which is also called congenital megacolon or intestinal aganglionosis, is characterized by an absence of enteric (intrinsic) neurons from variable lengths of the most distal bowel. Because enteric neurons are essential for propulsive intestinal motility, infants with HSCR suffer from severe constipation and have a distended abdomen. Currently the only treatment is surgical removal of the affected bowel. HSCR has an incidence of around 1:5,000 live births, with a 4:1 male:female gender bias. Most enteric neurons arise from neural crest cells that emigrate from the caudal hindbrain and then migrate caudally along the entire gut. The absence of enteric neurons from variable lengths of the bowel in HSCR results from a failure of neural crest-derived cells to colonize the affected gut regions. HSCR is therefore regarded as a neurocristopathy. HSCR is a multigenic disorder and has become a paradigm for understanding complex factorial disorders. The major HSCR susceptibility gene is RET. The penetrance of several mutations in HSCR susceptibility genes is sex-dependent. HSCR can occur as an isolated disorder or as part of syndromes; for example, Type IV Waardenburg syndrome is characterized by deafness and pigmentation defects as well as intestinal aganglionosis. Studies using animal models have shown that HSCR genes regulate multiple processes including survival, proliferation, differentiation, and migration. Research into HSCR and the development of enteric neurons is an excellent example of the cross fertilization of ideas that can occur between human molecular geneticists and researchers using animal models. WIREs Dev Biol 2013, 2:113-129. doi: 10.1002/wdev.57 For further resources related to this article, please visit the WIREs website.

BMP4 signaling mediates Zeb family in developing mouse tooth

Tooth morphogenesis is regulated by sequential and reciprocal interaction between oral epithelium and neural-crest-derived ectomesenchyme. The interaction is controlled by various signal molecules such as bone morphogenetic protein (BMP), Hedgehog, fibroblast growth factor (FGF), and Wnt. Zeb family is known as a transcription factor, which is essential for neural development and neural-crest-derived tissues, whereas the role of the Zeb family in tooth development remains unclear. Therefore, this study aimed to investigate the expression profiles of Zeb1 and Zeb2 during craniofacial development focusing on mesenchyme of palate, hair follicle, and tooth germ from E12.5 to E16.5. In addition, we examined the interaction between Zeb family and BMP4 during tooth development. Both Zeb1 and Zeb2 were expressed at mesenchyme of the palate, hair follicle, and tooth germ throughout the stages. In the case of tooth germ at the cap stage, the expression of Zeb1 and Zeb2 was lost in epithelium-separated dental mesenchyme. However, the expression of Zeb1 and Zeb2 in the dental mesenchyme was recovered by Bmp4 signaling via BMP4-soaked bead and tissue recombination. Our results suggest that Zeb1 and Zeb2, which were mediated by BMP4, play an important role in neural-crest-derived craniofacial organ morphogenesis, such as tooth development.