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

RET receptor signaling: dysfunction in thyroid cancer and Hirschsprung's disease

Gain-of-function mutations within the receptor tyrosine kinase gene RET cause inherited and non-inherited thyroid cancer. Somatic gene rearrangements of RET have been found in papillary thyroid carcinoma and germline point mutations in multiple endocrine neoplasia (MEN) types 2A and 2B and familial medullary thyroid carcinoma (FMTC). Conversely, loss-of-function mutations are responsible for the development of Hirschsprung's disease, a congenital malformation of the enteric nervous system. Comparison between normal RET signaling activated by the RET ligand glial cell line-derived neurotrophic factor (GDNF) and abnormal RET signaling caused by various mutations has led to a deeper understanding of disease mechanisms. The focus of the present review is on recent progress in the study of RET signaling dysfunction in human diseases.

A novel susceptibility locus for Hirschsprung's disease maps to 4q31.3-q32.3

We report on a multigenerational family with isolated Hirschsprung's disease (HSCR). Five patients were affected by either short segment or long segment HSCR. The family consists of two main branches: one with four patients (three siblings and one maternal uncle) and one with one patient. Analysis of the RET gene, the major gene involved in HSCR susceptibility, revealed neither linkage nor mutations. A genome wide linkage analysis was performed, revealing suggestive linkage to a region on 4q31-q32 with a maximum parametric multipoint LOD score of 2.7. Furthermore, non-parametric linkage (NPL) analysis of the genome wide scan data revealed a NPL score of 2.54 (p = 0.003) for the same region on chromosome 4q (D4S413-D4S3351). The minimum linkage interval spans a region of 11.7 cM (12.2 Mb). No genes within this chromosomal interval have previously been implicated in HSCR. Considering the low penetrance of disease in this family, the 4q locus may be necessary but not sufficient to cause HSCR in the absence of modifying loci elsewhere in the genome. Our results suggest the existence of a new susceptibility locus for HSCR at 4q31.3-q32.3.

The contribution of associated congenital anomalies in understanding Hirschsprung's disease

Hirschsprung's disease (HSCR) is a complex congenital disorder which, from a molecular perspective, appears to result due to disruption of normal signalling during development of enteric nerve cells, resulting in aganglionosis of the distal bowel. Associated congenital anomalies occur in at least 5-32% (mean 21%) of patients and certain syndromic phenotypes have been linked to distinct genetic sites, indicating underlying genetic associations of the disease and probable gene-gene interaction in its pathogenesis. Clear-cut associations with HSCR include Down's syndrome, dominant sensorineural deafness, Waardenburg syndrome, neurofibromatosis, neuroblastoma, phaeochromocytoma, the MEN type IIB syndrome and other abnormalities. Individual anomalies vary from 2.97% to 8%, the most frequent being the gastrointestinal tract (GIT) (8.05%), the central nervous system (CNS) and sensorineural anomalies (6.79%) and the genito-urinary tract (6.05%). Other associated systems include the musculoskeletal (5.12%), cardiovascular systems (4.99%), craniofacial and eye abnormalities (3%) and less frequently the skin and integumentary system (ectodermal dysplasia) and syndromes related to cholesterol and fat metabolism. In addition to associations with neuroblastoma and tumours related to MEN2B, HSCR may also be associated with tumours of neural origin such as ganglioneuroma, ganglioneuroblastoma, retinoblastoma and tumours associated with neurofibromatosis and other autonomic nervous system disturbances. The contribution of the major susceptibility genes on chromosome 10 (RET) and chromosome 13 (EDNRB) is well established in the phenotypic expression of HSCR. Whereas major RET mutations may result in HSCR by haploinsufficiency in 20-25% of cases, the etiology of the majority of sporadic HSCR is not as clear, appearing to arise from the combined cumulative effects of susceptibility loci at critical genes controlling the mechanisms of cell proliferation, differentiation and maturation. In addition, potential "modifying" associations exist with chromosome 2, 9, 20, 21 and 22, and we explore the importance of certain flanking genes of critical areas in the final phenotypic expression of HSCR.

Microcephaly, lissencephaly, Hirschsprung disease and tetralogy of Fallot: a new syndrome?

We report an 8-month-old girl with extreme microcephaly, lissencephaly, tetralogy of Fallot and Hirschsprung disease. She has a history of infantile spasms with developmental stagnation. Various diagnoses were considered but none seem to fit her clinical presentation. This combination of findings has not been described in the past and we suggest that this may be a previously undescribed neurodevelopmental syndrome resulting from a global failure of neuronal migration.

A missense mutation in theZFHX1B gene associated with an atypical Mowat–Wilson syndrome phenotype

Mowat-Wilson syndrome (MWS) is a rare mental retardation-multiple congenital anomalies syndrome associated with typical facial dysmorphism. Patients can show a variety of other anomalies like short stature, microcephaly, Hirschsprung disease, malformations of the brain, seizures, congenital heart defects and urogenital anomalies. Mutations leading to haploinsufficiency of the ZFHX1B gene have been described as the underlying cause of this condition. We report on the clinical findings in a 2(1/2)-year-old boy with some aspects out of the MWS-spectrum in addition to unusual anomalies and a novel missense mutation in the ZFHX1B gene.

Clinical features and management issues in Mowat–Wilson syndrome

Mowat-Wilson syndrome (MWS) is a relatively newly described multiple congenital anomaly/mental retardation syndrome. Haploinsufficiency of a gene termed ZFHX1B (also known as SIP1) on chromosome 2 is responsible for this condition, and clinical genetic testing for MWS recently became available. The majority of reports in the literature originate from Northern Europe and Australia. Here we report our clinical experience with 12 patients diagnosed with MWS within a 2-year period of time in the United States, with particular emphasis on clinical characteristics and management strategies. Individuals with this condition have characteristic facial features, including microcephaly, hypertelorism, medially flared and broad eyebrows, prominent columella, pointed chin, and uplifted earlobes, which typically prompt the clinician to consider the diagnosis. Medical issues in our cohort of patients included seizures (75%) with no predeliction for any particular seizure type; agenesis of the corpus callosum (60% of our patients studied); congenital heart defects (75%), particularly involving the pulmonary arteries and/or valves; hypospadias (55% of males); severely impaired or absent speech (100% of individuals over 1 year of age) with relatively spared receptive language; and Hirschsprung disease (50%) or chronic constipation (25%). The incidence of MWS is unknown, but based on the number of patients identified in a short period of time within the US, it is likely greatly under recognized. MWS should be considered in any individual with severely impaired or absent speech, especially in the presence of seizures and anomalies involving the pulmonary arteries (particularly pulmonary artery sling) or pulmonary valves.

Complementary expression pattern ofZfhx1 genesSip1 andδEF1 in the mouse embryo and their genetic interaction revealed by compound mutants

In mouse embryos, the Zfhx1 transcription factor genes, Sip1 and deltaEF1, are expressed in complementary domains in many tissues. Their possible synergism in embryogenesis was investigated by comparing the phenotype of Sip1-/-;deltaEF1-/- double homozygotes with single homozygous embryos. Unexpectedly, in Sip1-/- embryos deltaEF1 was ectopically activated, suggesting a negative regulation of deltaEF1 expression by Sip1. Sip1-/-;deltaEF1-/- embryos were similar to Sip1-/- embryos in short somite production and developmental arrest around E8.5, but showed more severe defects in dorsal neural tube morphogenesis accompanied by a larger reduction of Sox2 expression, ascribable to the loss of the ectopic deltaEF1 expression. Sip1+/-;deltaEF1-/- embryos develop various morphological defects after E10 that were absent in deltaEF1-/- embryos even in tissues without significant overlap of Sip1 and deltaEF1 expression, and arrested during mid gestation earlier than deltaEF1-/- embryos. These findings indicate that complex synergistic interactions occur between Zfhx1 transcription factor genes during mouse embryogenesis.

Reduced endothelin converting enzyme-1 and endothelin-3 mRNA in the developing bowel of male mice may increase expressivity and penetrance of Hirschsprung disease–like distal intestinal aganglionosis

Hirschsprung disease (distal intestinal aganglionosis, HSCR) is a multigenic disorder with incomplete penetrance, variable expressivity, and a strong male gender bias. Recent studies demonstrated that these genetic patterns arise because gene interactions determine whether enteric nervous system (ENS) precursors successfully proliferate and migrate into the distal bowel. We now demonstrate that male gender bias in the extent of distal intestinal aganglionosis occurs in mice with Ret dominant-negative mutations (RetDN) that mimic human HSCR. We hypothesized that male gender bias could result from reduced expression of a gene already known to be essential for ENS development. Using quantitative real-time polymerase chain reaction (PCR) we demonstrated reduced levels of endothelin converting enzyme-1 and endothelin-3 mRNA in the male mouse bowel at the time that ENS precursors migrate into the colon. Other HSCR-associated genes are expressed at comparable levels in male and female mice. Testosterone and Mullerian inhibiting substance had no deleterious effect on ENS precursor development, but adding EDN3 peptide to E11.5 male RetDN heterozygous mouse gut explants in organ culture significantly increased the rate of ENS precursor migration through the bowel.

Epithelial-mesenchymal transition in development and cancer: role of phosphatidylinositol 3' kinase/AKT pathways

Epithelial-mesenchymal transition (EMT) is an important process during development by which epithelial cells acquire mesenchymal, fibroblast-like properties and show reduced intercellular adhesion and increased motility. Accumulating evidence points to a critical role of EMT-like events during tumor progression and malignant transformation, endowing the incipient cancer cell with invasive and metastatic properties. Several oncogenic pathways (peptide growth factors, Src, Ras, Ets, integrin, Wnt/beta-catenin and Notch) induce EMT and a critical molecular event is the downregulation of the cell adhesion molecule E-cadherin. Recently, activation of the phosphatidylinositol 3' kinase (PI3K)/AKT axis is emerging as a central feature of EMT. In this review, we discuss the role of PI3K/AKT pathways in EMT during development and cancer with a focus on E-cadherin regulation. Interactions between PI3K/AKT and other EMT-inducing pathways are presented, along with a discussion of the therapeutic implications of modulating EMT in order to achieve cancer control.

Reiterated Wnt and BMP signals in neural crest development

Common signaling pathways such as those for Wnts and BMPs are used many times during embryogenesis. During the development of the neural crest, Wnt and BMP signals are used repeatedly at different stages to influence initial induction, segregation from the neuroepithelium and cell fate determination. This review considers how specificity is generated within the neural crest for these reiterated signals, discussing examples of how the outcomes of signaling events are modulated by context.

SIP1/ZEB2 induces EMT by repressing genes of different epithelial cell-cell junctions

SIP1/ZEB2 is a member of the deltaEF-1 family of two-handed zinc finger nuclear factors. The expression of these transcription factors is associated with epithelial mesenchymal transitions (EMT) during development. SIP1 is also expressed in some breast cancer cell lines and was detected in intestinal gastric carcinomas, where its expression is inversely correlated with that of E-cadherin. Here, we show that expression of SIP1 in human epithelial cells results in a clear morphological change from an epithelial to a mesenchymal phenotype. Induction of this epithelial dedifferentiation was accompanied by repression of several cell junctional proteins, with concomitant repression of their mRNA levels. Besides E-cadherin, other genes coding for crucial proteins of tight junctions, desmosomes and gap junctions were found to be transcriptionally regulated by the transcriptional repressor SIP1. Moreover, study of the promoter regions of selected genes by luciferase reporter assays and chromatin immunoprecipitation shows that repression is directly mediated by SIP1. These data indicate that, during epithelial dedifferentiation, SIP1 represses in a coordinated manner the transcription of genes coding for junctional proteins contributing to the dedifferentiated state; this repression occurs by a general mechanism mediated by Smad Interacting Protein 1 (SIP1)-binding sites.

RET tyrosine kinase signaling in development and cancer

The variety of diseases caused by mutations in RET receptor tyrosine kinase provides a classic example of phenotypic heterogeneity. Gain-of-function mutations of RET are associated with human cancer. Gene rearrangements juxtaposing the tyrosine kinase domain to heterologous gene partners have been found in sporadic papillary carcinomas of the thyroid (PTC). These rearrangements generate chimeric RET/PTC oncogenes. In the germline, point mutations of RET are responsible for multiple endocrine neoplasia type 2 (MEN 2A and 2B) and familial medullary thyroid carcinoma (FMTC). Both MEN 2 mutations and PTC gene rearrangements potentiate the intrinsic tyrosine kinase activity of RET and, ultimately, activate the RET downstream targets. Loss-of-function mutations of RET cause Hirschsprung's disease (HSCR) or colonic aganglionosis. A deeper understanding of the molecular signaling of normal versus abnormal RET activity in cancer will enable the development of potential new treatments for patients with sporadic and inherited thyroid cancer or MEN 2 syndrome. We now review the role and mechanisms of RET signaling in development and carcinogenesis.

Variations in aganglionic segment length of the enteric neural plexus in Mowat-Wilson syndrome

BACKGROUND/PURPOSE

Patients with zinc finger homeo box 1B (ZFHX1B) mutations or deletions develop multiple congenital anomalies including Hirschsprung disease, known as Mowat-Wilson syndrome (MWS). In this study, we investigated variations in the enteric neural plexus abnormalities in MWS using morphometry-based histopathologic analysis.

METHODS

Seven patients with MWS (3 with mutations in exon 8 of ZFHX1B and 4 with deletions) who had undergone modified Duhamel's operations for Hirschsprung disease were examined. Surgically resected rectosigmoid specimens were analyzed morphometrically.

RESULTS

The length of the aganglionic segment was longer than 3 cm in all the patients with deletions. In 3 patients with mutations, the aganglionic region was not detected in the surgically resected specimens; however, the parameters of the ganglions and plexus were significantly smaller than those of controls (cloaca and aproctia), indicative of a transitional zone. Variation in the severity of pathological changes among the 3 patients with mutations was also noted.

CONCLUSIONS

The variations in myenteric plexus pathologies in MWS appear to be caused by both variations in ZFHX1B abnormalities and epigenetic factors.

Studying the genetics of Hirschsprung's disease: unraveling an oligogenic disorder

Hirschsprung's disease is characterized by the absence of ganglion cells in the myenteric and submucosal plexuses of the gastrointestinal tract. Genetic dissection was successful as nine genes and four loci for Hirschsprung's disease susceptibility were identified. Different approaches were used to find these loci such as classical linkage in large families, identity by descent mapping in an inbred kindred, candidate gene approaches based on naturally occurring mutant mice models, and finally the use of model-free linkage and association analyzes. In this study, we review the identification of genes and loci involved in the non-syndromic common form and syndromic Mendelian forms of Hirschsprung's disease. The majority of the identified genes are related to Mendelian syndromic forms of Hirschsprung's disease. The non-Mendelian inheritance of sporadic non-syndromic Hirschsprung's disease proved to be complex; involvement of multiple loci was demonstrated in a multiplicative model. We discuss the practical implications of the elucidation of genes associated with Hirschsprung's disease susceptibility for genetic counseling. Finally, we speculate on possible strategies to identify new genes for Hirschsprung's disease.

Homozygous nonsense mutations in KIAA1279 are associated with malformations of the central and enteric nervous systems

We identified, by homozygosity mapping, a novel locus on 10q21.3-q22.1 for Goldberg-Shprintzen syndrome (GOSHS) in a consanguineous Moroccan family. Phenotypic features of GOSHS in this inbred family included microcephaly and mental retardation, which are both central nervous system defects, as well as Hirschsprung disease, an enteric nervous system defect. Furthermore, since bilateral generalized polymicogyria was diagnosed in all patients in this family, this feature might also be considered a key feature of the syndrome. We demonstrate that homozygous nonsense mutations in KIAA1279 at 10q22.1, encoding a protein with two tetratrico peptide repeats, underlie this syndromic form of Hirschsprung disease and generalized polymicrogyria, establishing the importance of KIAA1279 in both enteric and central nervous system development.

Genitourinary anomalies in Mowat-Wilson syndrome with deletion/mutation in the zinc finger homeo box 1B gene (ZFHX1B). Report of three Italian cases with hypospadias and review

Hypospadias, when the urethra opens on the ventral side of the penis, is a common malformation seen in about 3 per 1,000 male births. It is a complex disorder associated with genetic and environmental factors and can be part of genetic syndromes. Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by a distinct facial phenotype, Hirschsprung disease, microcephaly and mental retardation. It is caused by mutations in the zinc finger homeo box 1B gene, ZFHX1B (SIP1). To date, 68 deletion/mutation-positive cases have been reported. Genitourinary anomalies are common in MWS. Here we report that hypospadias is common in males with this syndrome. In 39 patients where this information was available, hypospadias was present in 46% of patients (18/39). In the 3 Italian male cases reported here, hypospadias was always present. MWS should be considered by endocrinologists in patients with hypospadias associated with developmental delays/mental retardation, in particular in the presence of a distinct facial phenotype.

Multiple endocrine neoplasia type 2B and Hirschsprung's disease

Multiple endocrine neoplasia type 2B and Hirschsprung's disease are genetic disorders characterized by gross and/or microscopic pathology of the enteric nervous system and associated dysmotility. A specific missense mutation in the RET proto-oncogene is the etiology of multiple endocrine neoplasia type B, in contrast to very complex multigenetic defects that underlie Hirschsprung's disease, which include overt mutations and more subtle changes in the RET locus. In this review, the molecular genetics of the 2 conditions are discussed, and the clinical implications of existing data and future studies are summarized.

Low RET mutation frequency and polymorphism analysis of the RET and EDNRB genes in patients with Hirschsprung disease in Taiwan

Hirschsprung disease (HSCR), or congenital intestinal aganglionosis, is a relatively common disorder characterized by the absence of ganglion cells in the nerve plexuses of the lower digestive tract, resulting in intestinal obstruction in neonates. Mutations in genes of the RET receptor tyrosine kinase and endothelin receptor B (EDNRB) signaling pathways have been shown to be associated in HSCR patients. In this study, we collected genomic DNA samples from 55 HSCR patients in central Taiwan and analyzed the coding regions of the RET and EDNRB genes by PCR amplification and DNA sequencing. In the 55 patients, an A to G transition was detected in two (identical twin brothers). The mutation was at the end of RET exon 19 at codon 1062 (Y1062C), a reported critical site for the signaling pathways. Single nucleotide polymorphisms (SNP) in exons 2, 7, 11, 13, and 15 of RET and exon 4 of EDNRB in the HSCR patients or controls were detected. The differences between patients and controls in allele distribution of the five RET polymorphic sites were statistically significant. The most frequent genotype encompassing exons 2 and 13 SNPs (the polymorphic sites with the highest percentage of heterozygotes) was AA/GG in patients, which was different from the AG/GT in the normal controls. Transmission disequilibrium was observed in exons 2, 7, and 13, indicating nonrandom association of the susceptibility alleles with the disease in the patients. This study represents the first comprehensive genetic analysis of HSCR disease in Taiwan.

Clinical and Mutational Spectrum of Mowat–Wilson Syndrome

Mowat-Wilson Syndrome is a recently delineated mental retardation syndrome usually associated with multiple malformations and a recognizable facial phenotype caused by defects of the transcriptional repressor ZFHX1B. To address the question of clinical and mutational variability, we analysed a large number of patients with suspected Mowat-Wilson Syndrome (MWS). Without prior knowledge of their mutational status, 70 patients were classified into "typical MWS", "ambiguous" and "atypical" groups according to their facial phenotype. Using FISH, qPCR and sequencing, ZFHX1B deletions, splice site or truncating mutations were detected in all 28 patients classified as typical MWS. No ZFHX1B defect was apparent in the remaining 15 cases with ambiguous facial features or in the 27 atypical patients. Genotype-phenotype analysis confirmed that ZFHX1B deletions and stop mutations result in a recognizable facial dysmorphism with associated severe mental retardation and variable malformations such as Hirschsprung disease and congenital heart defects. Our findings indicate that structural eye anomalies such as microphthalmia should be considered as part of the MWS spectrum. We also show that agenesis of the corpus callosum and urogenital anomalies (especially hypospadias) are significant positive predictors of a ZFHX1B defect. Based on our observation of affected siblings and the number of MWS cases previously reported, we suggest a recurrence risk of around 1%. The lack of missense mutations in MWS and MWS-like patients suggests there may be other, as yet unrecognized phenotypes, associated with missense mutations of this transcription factor.

Ocular coloboma and high myopia with Hirschsprung disease associated with a novel ZFHX1B missense mutation and trisomy 21

Syndromic Hirschsprung disease has been associated with mutations in ZFHX1B, a Smad-interacting transcriptional repressor protein. Tissue in situ hybridization has demonstrated strong expression of ZFHX1B in the developing eye, suggesting that some mutations in this gene may cause visual loss. However, none of the reported mutations have been associated with an ocular phenotype. We describe a patient with Down syndrome and Hirschsprung disease with high myopia and ocular coloboma affecting the iris and retina. In addition to trisomy 21, a novel, de novo heterozygous A to G transition in exon 8 of the ZFHX1B gene was identified, which results in a R953G amino acid substitution. This abnormality was not seen in a screen of 200 chromosomes from ethnically matched, normal controls. The arginine residue at position 953 is an extremely conserved amino acid throughout evolution. This is the first report associating Hirschsprung disease and severe eye defects with a specific genetic mutation and is the first report of a mutation in ZFHX1B causing a developmental ocular anomaly.

Tumor metastasis: a new twist on epithelial-mesenchymal transitions

Epithelial-mesenchymal transitions are essential for normal embryonic development and for progression of non-invasive tumor cells into malignant, metastatic carcinomas. Twist, an important regulator of morphogenesis in the embryo, has recently been implicated in the onset of invasive behavior during tumor progression.

Identification of Sox8 as a modifier gene in a mouse model of Hirschsprung disease reveals underlying molecular defect

Mice carrying heterozygous mutations in the Sox10 gene display aganglionosis of the colon and represent a model for human Hirschsprung disease. Here, we show that the closely related Sox8 functions as a modifier gene for Sox10-dependent enteric nervous system defects as it increases both penetrance and severity of the defect in Sox10 heterozygous mice despite having no detectable influence on enteric nervous system development on its own. Sox8 exhibits an expression pattern very similar to Sox10 with occurrence in vagal and enteric neural crest cells and later confinement to enteric glia. Loss of Sox8 alleles in Sox10 heterozygous mice impaired colonization of the gut by enteric neural crest cells already at early times. Whereas proliferation, apoptosis, and neuronal differentiation were normal for enteric neural crest cells in the gut of mutant mice, apoptosis was dramatically increased in vagal neural crest cells outside the gut. The defects in enteric nervous system development of mice with Sox10 and Sox8 mutations are therefore likely caused by a reduction of the pool of undifferentiated vagal neural crest cells. Our study suggests that Sox8 and Sox10 are jointly required for the maintenance of these vagal neural crest stem cells.

Recurrence of Mowat-Wilson syndrome in siblings with the same proven mutation

Mowat-Wilson syndrome (MWS) is a mental retardation syndrome associated with distinctive facial features, microcephaly, epilepsy, and a variable spectrum of congenital anomalies, including Hirschsprung disease (HSCR), agenesis of the corpus callosum, genitourinary abnormalities, and congenital heart disease. Heterozygous mutations or deletions involving the gene ZFHX1B (previously SIP1) [OMIM 605802] have recently been found to cause MWS. There have previously been no reports of a sibling recurrence of this syndrome. A brother and sister are described with clinical features of MWS, where both have the same truncating mutation in exon 8 of ZFHX1B. As their parents are phenotypically normal and do not have the mutation in lymphocyte-derived DNA, the most likely explanation is germ-line mosaicism.

Hirschsprung's disease in Japan: analysis of 3852 patients based on a nationwide survey in 30 years

BACKGROUND/PURPOSE

The introduction of laparoscope and transanal endorectal pull-through has caused a revolution in the operative procedures for Hirschsprung's disease. To study the changing profile of Hirschsprung's disease in Japan, the authors carried out a national survey.

METHOD

Patient data were collected in 3 phases: group 1, 1628 patients between 1978 and 1982; group 2, 1121 patients between 1988 and 1992; and group 3, 1103 patients between 1998 and 2002, respectively.

RESULTS

The incidence was 1:4697, 1:5544, and 1:5343 and the male/female ratio was 3.0:1, 3.4:1, and 3.0:1 in each group, respectively. Patients weighing less than 2500 g at birth increased to 10.4% in group 3, whereas they were 6.5% in group 2 and 5.5% in group 1. The patients with a family history also increased to 6.0% in group 3, in comparison with 2.8% in group 2 and 3.0% in group 1. The incidence of associated anomalies increased over time, 11.1% in group 1, 16.3% in group 2, and 21.2% in group 3. Mutations of genes were found in 4 of the 23 patients examined. The extent of aganglionosis was almost the same in each group. Regarding the definitive operation, the procedures without laparotomy, including transanal endorectal pull-through, increased up to 42.6% in group 3 but 0% in groups 1 and 2. The frequency that a primary operation without stoma was performed also increased. The age at definitive operation decreased in group 3. The incidence of preoperative and postoperative enterocolitis also decreased over time. The mortality was decreased over time, 7.1%, 4.9%, and 3.0% for groups 1, 2, and 3, respectively.

CONCLUSIONS

The authors analyzed 3852 Japanese patients over 3 decades. The ratio of patients with a low birth weight, associated anomalies, or a family history was increased in the last 10 years. A primary operation without laparotomy has thus become the procedure of choice for a definitive operation.

XSIP1 is essential for early neural gene expression and neural differentiation by suppression of BMP signaling

Neural differentiation is induced by inhibition of BMP signaling. Secreted inhibitors of BMP such as Chordin from the Spemann organizer contribute to the initial step of neural induction. Xenopus Smad-interacting protein-1 gene (XSIP1) is expressed in neuroectoderm from the early gastrula stage through to the neurula stage. XSIP1 is able to inhibit BMP signaling and overexpression of XSIP1 induces neural differentiation. To clarify the function of XSIP1 in neural differentiation, we performed a loss-of-function study of XSIP1. Knockdown of XSIP1 inhibited SoxD expression and neural differentiation. These results indicate that XSIP1 is essential for neural induction. Furthermore, loss-of-function experiments showed that SoxD is essential for XSIP1 transcription and for neural differentiation. However, inhibition of XSIP1 translation prevented neural differentiation induced by SoxD; thus, SoxD was not sufficient to mediate neural differentiation. Expression of XSIP1 was also required for inhibition of BMP signaling. Together, these results suggest that XSIP1 and SoxD interdependently function to maintain neural differentiation.

Highly conserved upstream sequences for transcription factor genes and implications for the regulatory network

Identifying evolutionarily conserved blocks in orthologous genomic sequences is an effective way to detect regulatory elements. In this study, with the aim of elucidating the architecture of the regulatory network, we systematically estimated the degree of conservation of the upstream sequences of 3,750 human-mouse orthologue pairs along 8-kb stretches. We found that the genes with high upstream conservation are predominantly transcription factor (TF) genes. In particular, developmental process-related TF genes showed significantly higher conservation of the upstream sequences than other TF genes. Such extreme upstream conservation of the developmental process-related TF genes suggests that the regulatory networks involved with developmental processes have been evolutionarily well conserved in both human and mouse lineages.

TTF-1 and RET promoter SNPs: regulation of RET transcription in Hirschsprung's disease

Single nucleotide polymorphisms (SNPs) of the coding regions of receptor tyrosine kinase gene (RET) are associated with Hirschsprung's disease (HSCR, aganglionic megacolon). These SNPs, individually or combined, may act as a low penetrance susceptibility locus and/or be in linkage disequilibrium (LD) with another susceptibility locus located in RET regulatory regions. Because two RET promoter SNPs have been found associated with HSCR, in LD with HSCR-associated RET coding region haplotypes, their implication in the transcriptional regulation of RET is of major interest. Analysis of 172 sporadic HSCR patients also revealed the presence of HSCR-associated RET promoter SNPs in LD with the main coding region RET haplotype observed in Chinese patients. By using a weighted logistic regression approach, we determined that of all SNPs tested in our study, the promoter SNPs are the most correlated to the disease. Functional analysis of the RET promoter SNPs in the context of additional 5' regulatory regions demonstrated that the HSCR-associated alleles decrease RET transcription. These SNPs overlap a TTF-1 binding site and TTF-1-activated RET transcription is also decreased by the HSCR-associated SNPs. Moreover, we identified an HSCR patient with a Gly322Ser TTF-1 mutation that compromises activation of transcription from HSCR-associated RET promoter haplotypes. Interestingly, we show that the pattern of RET and TTF-1 expression is coincident in developing human gut. We also present a detailed profile of the RET gene in our population, which provides an insight into the higher incidence of the disease in China.

Detection of an interstitial deletion of 2q21-22 by high resolution comparative genomic hybridization in a child with multiple congenital anomalies and an apparent balanced translocation

Various molecular cytogenetic techniques are currently available to accurately characterize chromosome rearrangements in patients with multiple congenital anomalies. Among these is comparative genomic hybridization (CGH) whose main advantage is the ability to perform a whole genome scan without prior knowledge of the underlying chromosome abnormality. It has been used mostly in the area of cancer cytogenetics, but its role in clinical genetics is now expanding to even include preimplantation genetic diagnosis. We have used this method to reveal an interstitial deletion in a patient with multiple anomalies, who had for years been thought to have a de novo balanced translocation involving chromosomes 1 and 2. A review of published reports suggests that there is significant phenotypic and genetic heterogeneity in the small group of patients including our own with interstitial deletions of 2q21-q22.

Bone morphogenetic protein-2 and -4 limit the number of enteric neurons but promote development of a TrkC-expressing neurotrophin-3-dependent subset

The hypothesis that BMPs (bone morphogenetic proteins), which act early in gut morphogenesis, also regulate specification and differentiation in the developing enteric nervous system (ENS) was tested. Expression of BMP-2 and BMP-4, BMPR-IA (BMP receptor subunit), BMPR-IB, and BMPR-II, and the BMP antagonists, noggin, gremlin, chordin, and follistatin was found when neurons first appear in the primordial bowel at embryonic day 12 (E12). Agonists, receptors, and antagonists were detected in separated populations of neural crest- and noncrest-derived cells. When applied to immunopurified E12 ENS precursors, BMP-2 and BMP-4 induced nuclear translocation of phosphorylated Smad-1 (Sma and Mad-related protein). The number of neurons developing from these cells was increased by low concentrations and decreased by high concentrations of BMP-2 or BMP-4. BMPs induced the precocious appearance of TrkC-expressing neurons and their dependence on neurotrophin-3 for survival. BMP-4 interacted with glial cell line-derived neurotrophic factor (GDNF) to enhance neuronal development but limited GDNF-driven expansion of the precursor pool. BMPs also promoted development of smooth muscle from mesenchymal cells immunopurified at E12. To determine the physiological significance of these observations, the BMP antagonist noggin was overexpressed in the developing ENS of transgenic mice under the control of the neuron-specific enolase promoter. Neuronal numbers in both enteric plexuses and smooth muscle were increased throughout the postnatal small intestine. These increases were already apparent by E18. In contrast, TrkC-expressing neurons decreased in both plexuses of postnatal noggin-overexpressing animals, again an effect detectable at E18. BMP-2 and/or BMP-4 thus limit the size of the ENS but promote the development of specific subsets of enteric neurons, including those that express TrkC.

Pleiotropic and diverse expression of ZFHX1B gene transcripts during mouse and human development supports the various clinical manifestations of the "Mowat-Wilson" syndrome

ZFHX1B encodes Smad-interacting protein 1, a transcriptional corepressor involved in the transforming growth factors beta (TGFbeta) signaling pathway. ZFHX1B mutations cause a complex developmental phenotype characterized by severe mental retardation (MR) and multiple congenital defects. We compared the distribution of ZFHX1B transcripts during mouse and human embryogenesis as well as in adult mice and humans. This showed that this gene is strongly transcribed at an early stage in the developing peripheral and central nervous systems of both mice and humans, in all neuronal regions of the brains of 25-week human fetuses and adult mice, and at varying levels in numerous nonneural tissues. Northern blot analysis suggested that ZFHX1B undergoes tissue-specific alternative splicing in both species. These results strongly suggest that ZFHX1B determines the transcriptional levels of target genes in various tissues through the combinatorial interactions of its isoforms with different Smad proteins. Thus, as well as causing neural defects, ZFHX1B mutations may also cause other malformations.

Organization of the mouse Zfhx1b gene encoding the two-handed zinc finger repressor Smad-interacting protein-1

SIP1, a member of the deltaEF1 family of two-handed zinc finger transcriptional repressors, has been identified as a Smad-binding protein. Recently, mutations in the human SIP1 gene (ZFHX1B) have been implicated in Hirschsprung disease. Here we document extensively the structure and transcriptional pattern of the mouse SIP1 gene (Zfhx1b) and compare it to homologues from other species. The overall structure of Zfhx1b is highly similar to that of the deltaEF1 gene (Zfhx1a), confirming their close evolutionary relationship. In contrast to Zfhx1a, the 5' untranslated region of the SIP1-encoding mouse gene is very complex and includes several alternative exons. The corresponding 5'-UTR splicing pattern seems to be conserved between species and suggests a role in its transcriptional and/or translational regulation. The gene also codes for an antisense transcript that is highly conserved between human and mouse.

Localizing a putative mutation as the major contributor to the development of sporadic Hirschsprung disease to the RET genomic sequence between the promoter region and exon 2

Hirschsprung disease (HSCR), a congenital disorder characterized by intestinal obstruction due to absence of enteric ganglia along variable lengths of the intestinal tract, occurs both in familial and sporadic cases. RET mutations have been found in approximately 50% of the families, but explains only a minority of sporadic cases. This study aims at investigating a possible role of RET in sporadic HSCR patients. Haplotypes of 13 DNA markers, within and flanking RET, have been determined for 117 sporadic HSCR patients and their parents. Strong association was observed for six markers in the 5' region of RET. The largest distortions in allele transmission were found at the same markers. One single haplotype composed of these six markers was present in 55.6% of patients versus 16.2% of controls. Odds ratios (ORs) revealed a highly increased risk of homozygotes for this haplotype to develop HSCR (OR>20). These results allowed us to conclude that RET plays a crucial role in HSCR even when no RET mutations are found. An unknown functional disease variant(s) with a dosage-dependent effect in HSCR is likely located between the promoter region and exon 2 of RET.

TGF-beta signaling in human skeletal and patterning disorders

Members of the transforming growth factor beta (TGF-beta) family of multifunctional peptides are involved in almost every aspect of development. Model systems, ranging from genetically tractable invertebrates to genetically engineered mice, have been used to determine the mechanisms of TGF-beta signaling in normal development and in pathological situations. Furthermore, mutations in genes for the ligands, receptors, extracellular modulators, and intracellular signaling molecules have been associated with several human disorders. The most common are those associated with the development and maintenance of the skeletal system and axial patterning. This review focuses on the mechanisms of TGF-beta signaling with special emphasis on the molecules involved in human disorders of patterning and skeletal development.

Mutation of RET oncogene and endo-thelin B receptor gene in Hirschpru-ng's disease

AIM: To clarify the relationship between the mutation of RET and EDNRB genes and Chinese patients with Hirschspr-ung's disease (HD), and to investigate whether the two genes mutation concurred in the disease.

METHODS: Patients with HD were divided into RET/EDNRB group (group A, 56 cases) and ENDRB group (group B, 40 cases) at random. Healthy children were use as controls (group C, 56 and 40 cases). Genomic DNA was obtained from peripheral blood, then the exons 6, 13, 15 and 17 of RET gene and the exons 4, 5 and 6 of EDNRB gene were analyzed for gene mutation. The mutation products were automatically sequenced.

RESULTS: In group A, two heterozygous mutations at exons 17 and 13 were discovered in 2 sporadic HD patients. Direct DNA sequence analysis identified gene polymorphisms, which showed CTG→CTT, and Leu769→Leu. The sporadic mutation rate was 4% (2/48). Two heterozygous mutations were discovered in 2 familial HD patients at exon 15. DNA sequence analysis displayed a missense mutation Lys889→Thr in one patient and two silent mutation at codons V906 and S909 in another (GTGAAGAGGAGCCA→GTTAAGAGGAGTCA). The familial mutation rate was 25% (2/8). One heterozygous mutation of EDNRB gene at exon 5 in a sporadic short segmental patient failed to sequence. In group B, one heterozygous mutation was discovered in a sporadic short segmental patient. DNA sequence showed a G to A transversion at nucleotide 831, which resulted in a silent mutation Leu 277→Leu. The mutation rate was 2.7%(1/37). No mutation was detected in three familial HD patients. In group C, RET and EDNRB genes were identified no mutation. The difference of the RET gene mutation between the familial and sporadic patients by statistical analysis was x² = 4.95 (P < 0.05), odds ratio (OR) = 8; 95%CI = 1.28-49.87.

CONCLUSION: The mutation of RET and EDNRB genes reliably has correlated with the pathogenesis of HD. The RET gene mutation rate in familial HD patients is 25% and majority of sporadic cases have mutation in EDNRB gene. No HD patient has the two genes mutation at the same time. The risk of familial patients to get HD is 8 times higher than that of sporadic patients, and the confidence interval is 95%.

Churchill, a zinc finger transcriptional activator, regulates the transition between gastrulation and neurulation

Gastrulation generates mesoderm and endoderm from embryonic epiblast; soon after, the neural plate is established within the epiblast-both events require FGF signaling. We describe a zinc finger transcriptional activator, Churchill (ChCh), which acts as a switch between different roles of FGF. FGF induces ChCh slowly; this activates Smad-interacting-protein-1 (Sip1), which blocks further induction of the mesoderm markers brachyury and Tbx6L by FGF. ChCh is first expressed as cells stop migrating through the primitive streak, and we show that it regulates cell ingression. We propose a simple mechanism by which FGF sensitizes cells to BMP signals. These results reveal that neural induction requires cessation of mesoderm formation at the midline in addition to the decision between epidermis and neural plate.

PMX2B, a new candidate gene for Hirschsprung's disease

Hirschsprung's (HSCR) disease is a congenital intestinal malformation of the enteric nervous system. It is a multigenic malformation and until now, eight genes have been involved in the etiology of this disease: genes encoding proteins of the RET signaling pathway (RET, GDNF and NTN), genes participating in the endothelin (EDN) type B receptor pathway (EDNRB, EDN3 and ECE-1), the SOX10 gene and the SIP1 gene that is mutated in syndromic forms of HSCR. Mutations of these genes are found in not more than 50-60% of affected individuals. Here, we report on the results of a molecular cytogenetic study performed in a girl who presented with a syndromic short segment HSCR associated with a de novo t(4;8)(p13;p22) translocation. A comparative genomic hybridization (CGH) study found a 4p12p13 deletion. A molecular characterization of this rearrangement showed that the 4p13 deletion was 5 Mb in length and included the paired mesoderm homeobox gene (PMX2B) (MIM 603851), a gene expressed in the human embryonic gut and essential for the development of autonomic neural crest derivatives. The present observation suggests that PMX2B haploinsuffciency might predispose to HSCR.

The genetics of Hirschsprung disease

Understanding the genetics of Hirschsprung disease will naturally expand our understanding of other neurocristopathies, the enteric nervous system, and autonomic system biology. As other disorders of gastrointestinal motility are investigated, genetics may resolve certain clinical questions. For example, isolated hypoganglionosis without aganglionosis has been reported as a primary cause of intestinal pseudo-obstruction. Is such hypoganglionosis merely a forme-fruste of Hirschsprung disease, or a result from an entirely different pathogenetic mechanism? Can irritable bowel syndrome or severe constipation be related to specific mutations, polymorphisms, or haplotypes? How might an understanding of derangements of the ENS be translated to understanding derangements of the CNS? Clearly, we should anticipate improved prognostication, counseling, and hopefully, therapies with future genetic insights.

Interaction between Smad-interacting protein-1 and the corepressor C-terminal binding protein is dispensable for transcriptional repression of E-cadherin

deltaEF1 and SIP1 (or Zfhx1a and Zfhx1b, respectively) are the only known members of the vertebrate Zfh1 family of homeodomain/zinc finger-containing proteins. Similar to other transcription factors, both Smad-interacting protein-1 (SIP1) and deltaEF1 are capable of repressing E-cadherin transcription through binding to the E2 boxes located in its promoter. In the case of deltaEF1, this repression has been proposed to occur via interaction with the corepressor C-terminal binding protein (CtBP). In this study, we show by coimmunoprecipitation that SIP1 and CtBP interact in vivo and that an isolated CtBP-binding SIP1 fragment depends on CtBP for transcriptional repression. However, and most importantly, full-length SIP1 and deltaEF1 proteins do not depend on their interaction with CtBP to repress transcription from the E-cadherin promoter. Furthermore, in E-cadherin-positive kidney epithelial cells, the conditional synthesis of mutant SIP1 that cannot bind to CtBP abrogates endogenous E-cadherin expression in a similar way as wild-type SIP1. Our results indicate that full-length SIP1 can repress E-cadherin in a CtBP-independent manner.

Further delineation of the phenotype associated with heterozygous mutations in ZFHX1B

Mutations or deletions involving ZFHX1B (previously SIP1) have recently been found to cause one form of syndromic Hirschsprung disease (HSCR), associated with microcephaly, mental retardation, and distinctive facial features. Patients with the characteristic facial phenotype and severe mental retardation, but without HSCR, have now also been shown to have mutations in this gene. Mutations of ZFHX1B are frequently associated with other congenital anomalies, including congenital heart disease, hypospadias, renal tract anomalies, and agenesis of the corpus callosum (ACC). We present the clinical data and mutation analysis results from a series of 23 patients with this clinical syndrome, of whom 21 have proven ZFHX1B mutations or deletions (15 previously unpublished). Two patients with the typical features (one with and one without HSCR) did not have detectable abnormalities of ZFHX1B. We emphasize that this syndrome can be recognized by the facial phenotype in the absence of either HSCR or other congenital anomalies, and needs to be considered in the differential diagnosis of dysmorphism with severe mental retardation +/- epilepsy.

Opposing functions of ZEB proteins in the regulation of the TGFbeta/BMP signaling pathway

Binding of TGFbeta/BMP factors to their receptors leads to translocation of Smad proteins to the nucleus where they activate transcription of target genes. The two-handed zinc finger proteins encoded by Zfhx1a and Zfhx1b, ZEB-1/deltaEF1 and ZEB-2/SIP1, respectively, regulate gene expression and differentiation programs in a number of tissues. Here I demonstrate that ZEB proteins are also crucial regulators of TGFbeta/BMP signaling with opposing effects on this pathway. Both ZEB proteins bind to Smads, but while ZEB-1/deltaEF1 synergizes with Smad proteins to activate transcription, promote osteoblastic differentiation and induce cell growth arrest, the highly related ZEB-2/SIP1 protein has the opposite effect. Finally, the ability of TGFbeta to mediate transcription of TGFbeta-dependent genes and induce growth arrest depends on the presence of endogenous ZEB-1/deltaEF1 protein.

RET and NTRK1 proto-oncogenes in human diseases

RET and NTRK1 are receptor tyrosine kinase (RTK) proteins which play a role in the development and maturation of specific component of the nervous system. Their alterations have been associated to several human diseases, including some forms of cancer and developmental abnormalities. These features have contributed to the concept that one gene can be responsible for more than one disease. Moreover, both genes encoding for the two RTKs show genetic alterations that belong to either "gain of function" or "loss of function" class of mutations. In fact, receptor rearrangements or point mutations convert RET and NTRK1 in dominantly acting transforming genes leading to thyroid tumors, whereas inactivating mutations, associated with Hirschsprung's disease (HSCR) and congenital insensitivity to pain with anhidrosis (CIPA), impair RET and NTRK1 functions, respectively. In this review we have summarized the main features of the two receptors, their physiological and pathological roles. In addition, we attempted to identify the correlations between the different genetic alterations and the related pathogenetic mechanisms.

Cys611Ser mutation in RET proto-oncogene in a kindred with medullary thyroid carcinoma and Hirschsprung's disease

Germline mutations in the RET proto-oncogene are responsible for the development of human hereditary diseases, including multiple endocrine neoplasia (MEN) type 2A and 2B, familial medullary thyroid carcinoma (FMTC), and Hirschsprung's disease (HSCR). It has been reported that some families developed both MEN 2A/FMTC and HSCR, in which a mutation in a cysteine residue at codon 609, 618, or 620 in the RET gene was present. Here we report a novel RET mutation detected in a Japanese family with medullary thyroid carcinoma and HSCR. A germline mutation in cysteine 611 of the RET gene was identified in this family, which introduced an amino-acid change from cysteine to serine. By biological and biochemical analyses of mutant RET proteins, we previously predicted the potentiality that amino-acid substitution for cysteine 611 as well as cysteines 609, 618, and 620 would promote the development of MEN 2A/FMTC and HSCR. This clinical case substantiates our suggestion for the mechanism of the development of both the diseases.

Mowat-Wilson syndrome

MWS is a multiple congenital anomaly syndrome, first clinically delineated by Mowat et al in 1998. Over 45 cases have now been reported. All patients have typical dysmorphic features in association with severe intellectual disability, and nearly all have microcephaly and seizures. Congenital anomalies, including Hirschsprung disease (HSCR), congenital heart disease, hypospadias, genitourinary anomalies, agenesis of the corpus callosum, and short stature are common. The syndrome is the result of heterozygous deletions or truncating mutations of the ZFHX1B (SIP1) gene on chromosome 2q22.