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

Mutated Transcripts of ZEB2 Do Not Undergo Nonsense-Mediated Decay in Mowat-Wilson Syndrome

Introduction

Mowat-Wilson syndrome (MWS) is an autosomal-dominant complex developmental disorder characterized by distinctive facial appearance, intellectual disability, epilepsy, and various clinically heterogeneous abnormalities reminiscent of neurocristopathies. MWS is caused by haploinsufficiency of ZEB2 due to heterozygous point mutations and copy number variations.

Case Presentation

We report on two unrelated affected individuals with novel ZEB2indel mutations, molecularly confirming the diagnosis of MWS. Quantitative real-time polymerase chain reaction (PCR) for the comparison of total transcript levels and allele-specific quantitative real-time PCR were also performed and demonstrated that the truncating mutations did not lead to nonsense-mediated decay as expected.

Conclusion

ZEB2 encodes a multifunctional pleiotropic protein. Novel mutations in ZEB2 should be reported in order that genotype-phenotype correlations might be established in this clinically heterogeneous syndrome. Further cDNA and protein studies may help elucidate the underlying pathogenetic mechanisms of MWS since nonsense-mediated RNA decay was found to be absent in only a few studies including this study.

First Case Report of Developmental Bilateral Cataract with a Novel Mutation in the ZEB2 Gene Observed in Mowat-Wilson Syndrome

Background: Mowat-Wilson syndrome (MWS) is extremely rare multisystemic autosomal dominant disorder caused by mutations in the Zinc Finger E-Box Binding Homeobox 2 (ZEB2) gene. Ocular pathologies are one of the symptoms that appear in the clinical picture of MWS individuals, but not many have been described so far. Pathologies such as optic nerve or retinal epithelium atrophy, iris or optic disc coloboma as well as congenital cataracts have been most frequently described until now. Therefore, we would like to report the first case of bilateral developmental cataract in a 9-year-old girl with MWS who underwent successful cataract surgery with intraocular lens implantation. Case Presentation: A 9-year-old girl, diagnosed with p.Gln694Ter mutation in ZEB2 gene and suspicion of MWS was referred to the Children's Outpatient Ophthalmology Clinic for ophthalmological evaluation. Her previous assessments revealed abnormalities of the optic nerve discs. The patient was diagnosed with atrophy of the optic nerves, convergent strabismus, and with-the-rule astigmatism. One year later, during the follow-up visit, the patient was presented with decreased visual acuity (VA), developmental total cataract in the right eye and a developmental partial cataract in the left eye. This resulted in decreased VA confirmed by deteriorated responses in visual evoked potential (VEP) test. The girl underwent a two-stage procedure of cataract removal, first of one eye and then of the other eye with artificial lens implants. In the 2 years following the operation, no complications were observed and, most remarkably, VA improved significantly. Conclusions: The ZEB2 gene is primarily responsible for encoding the Smad interaction protein 1 (SIP1), which is involved in the proper development of various eye components. When mutated, it results in multilevel abnormalities, also in the proper lens formation, that prevent the child from normal vision development. This typically results in the formation of congenital cataracts in children with MWS syndrome, however, our case shows that it also leads to the formation of developmental cataracts. This is presumably due to the effect of the lack of SIP1 on other genes, altering their downstream expression and is a novel insight into the importance of the SIP1 in the occurrence of ocular pathologies. To the best of our knowledge, this is the first case of bilateral developmental cataract in the context of MWS. Moreover, a novel mutation (p.Gln694Ter) in the ZEB2 gene was found corresponding to this syndrome entity. This report allows us to gain a more comprehensive insight into the genetic spectrum and the corresponding phenotypic features in MWS syndrome patients.

Mowat-Wilson Syndrome as a Differential Diagnosis in Patients with Congenital Heart Defects and Dysmorphic Facies

Mowat-Wilson syndrome is a rare, autosomal dominant neurodevelopmental disorder characterized by distinctive facial gestalt and intellectual disability that is often associated with microcephaly, seizures and multiple congenital anomalies, mainly heart defects. More than 350 patients and 180 genetic variants in the ZEB2 gene, have been reported with an estimated frequency of 1 per 70,000 births. Here we report a Colombian female patient with facial gestalt, intellectual disability, microcephaly, congenital heart defects, hypothyroidism and middle ear defect associated with the nonsense pathogenic variant c.2761C>T (p.Arg921Ter) in the ZEB2 gene. This case contributes to the understanding of the clinical complications and the natural history of this complex and clinically heterogeneous disorder but also to the awareness that patients with heart congenital defects and dysmorphic facies may present an underlying genetic disorder.

A Chinese Boy with Mowat-Wilson Syndrome Caused by a 10 bp Deletion in the ZEB2 Gene

Purpose

Mowat–Wilson syndrome (MWS) is a rare complex malformation syndrome which is characterized by typical facial dysmorphism, moderate to severe intellectual disability, global developmental delay, and multiple congenital anomalies. Here, we summarize the clinical characteristics and gene mutation analysis of a Chinese boy with MWS.

Patients and Methods

The clinical features of the patient were monitored. DNA extracted from peripheral blood was subjected to sequencing analysis. Then, the whole-exome sequencing was performed.

Results

A novel deletion mutation (c.1137_1146del TAGTATGTCT) was identified in exon 8 of the ZEB2 gene. The deletion mutation was predicted to produce a truncated protein (p.S380Nfs*13), resulting in haploinsufficiency. The patient presented with short stature, microcephaly, congenital heart defects, cryptorchidism, corpus callosum agenesis, global developmental delay, and intellectual disability. Furthermore, he demonstrated bilateral sensorineural hearing loss. This manifestation is less common in MWS. It is first reported in Chinese patients with MWS. Clinical follow-up showed that the facial features of MWS developed with time. The facial features of the patient were not obvious except for the uplifted ear lobes at the age of 3 months. At the age of 22 months, the facial characteristics of the patient included ocular hypertelorism, frontal bossing, rounded nasal tip, sparse eyebrows, prominent chin, widely spaced teeth, and uplifted ear lobes with a central depression.

Conclusion

A novel deletion mutation of the ZEB2 gene was identified. This work contributes to expanding the mutation spectra of MWS. Our results may reflect the variability of the phenotype in MWS.

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Neurological Phenotype of Mowat-Wilson Syndrome

Mowat-Wilson Syndrome (MWS) (OMIM # 235730) is a rare disorder due to ZEB2 gene defects (heterozygous mutation or deletion). The ZEB2 gene is a widely expressed regulatory gene, extremely important for the proper prenatal development. MWS is characterized by a specific facial gestalt and multiple musculoskeletal, cardiac, gastrointestinal, and urogenital anomalies. The nervous system involvement is extensive and constitutes one of the main features in MWS, heavily affecting prognosis and life quality of affected individuals. This review aims to comprehensively organize and discuss the neurological and neurodevelopmental phenotype of MWS. First, we will describe the role of ZEB2 in the formation and development of the nervous system by reviewing the preclinical studies in this regard. ZEB2 regulates the neural crest cell differentiation and migration, as well as in the modulation of GABAergic transmission. This leads to different degrees of structural and functional impairment that have been explored and deepened by various authors over the years. Subsequently, the different neurological aspects of MWS (head and brain malformations, epilepsy, sleep disorders, and enteric and peripheral nervous system involvement, as well as developmental, cognitive, and behavioral features) will be faced one at a time and extensively examined from both a clinical and etiopathogenetic point of view, linking them to the ZEB2 related pathways.

Clinical and Molecular Spectrum of Four Patients Diagnosed with Mowat-Wilson Syndrome

Mowat-Wilson syndrome (MWS) is a rare autosomal dominant syndrome characterized by distinctive facial features, congenital heart defects, Hirschsprung disease, genitourinary anomalies, various structural brain anomalies, and intellectual disability. Pathogenic mutations that result in haploinsufficiency in the ZEB2 gene cause MWS. In this study, we aimed to evaluate the clinical features and molecular analysis results of 4 MWS patients. All patients were examined by an expert clinical geneticist. Dysmorphological abnormalities were recorded. Data including demographic, clinical, and laboratory findings were obtained from hospital records. ZEB2 gene analysis was performed using a Sanger sequencing method. All patients had typical facial features of MWS such as widely spaced eyes, broad eyebrows with a medial flare, low-hanging columella, prominent or pointed chin, open-mouth expression, and uplifted earlobes. Four different heterozygous mutations were identified; 2 mutations were frameshift (c.246_247delGGinsC, c.980_980delG), 1 was nonsense (c.2083C>T), and 1 was splice site (c.808-2A>G). Two of them (c.246_247delGGinsC, c.980_980delG) have not been previously reported in the literature. By defining 2 novel mutations, this study contributes to the molecular spectrum of MWS, while also providing a further insight for genetic counseling. It also demonstrates the importance of dysmorphological examination in clinical diagnosis.

Hirschsprung's disease: clinical dysmorphology, genes, micro-RNAs, and future perspectives

On the occasion of the 100th anniversary of Dr. Harald Hirschsprung's death, there is a worldwide significant research effort toward identifying and understanding the role of genes and biochemical pathways involved in the pathogenesis as well as the use of new therapies for the disease harboring his name (Hirschsprung disease, HSCR). HSCR (aganglionic megacolon) is a frequent diagnostic and clinical challenge in perinatology and pediatric surgery, and a major cause of neonatal intestinal obstruction. HSCR is characterized by the absence of ganglia of the enteric nervous system, mostly in the distal gastrointestinal tract. This review focuses on current understanding of genes and pathways associated with HSCR and summarizes recent knowledge related to micro RNAs (miRNAs) and HSCR pathogenesis. While commonly sporadic, Mendelian patterns of inheritance have been described in syndromic cases with HSCR. Although only half of the patients with HSCR have mutations in specific genes related to early embryonic development, recent pathway-based analysis suggests that gene modules with common functions may be associated with HSCR in different populations. This comprehensive profile of functional gene modules may serve as a useful resource for future developmental, biochemical, and genetic studies providing insights into the complex nature of HSCR.