Diagnosis and management in Pitt-Hopkins syndrome: First international consensus statement

NRXN1-related disorders, attempt to better define clinical assessment

Background

NRXN1-related disorders are uncommonly reported. The clinical features of the disorders are wide and heterogeneous mainly consisting of undistinctive facial dysmorphism, mild to severe intellectual and speech delay, epileptic seizures, and motor dysfunction. Defects in NRXN1 gene have been identified in cases diagnosed as Pitt-Hopkins-like-syndrome 2 (PTHLS2; OMIM#614325).

Methods

Literature review of NRXN1-related disorders was conducted and main clinical features of individuals affected by these disorders were analyzed. In addition, clinical features of individuals labelled with PTHSL2 diagnosis were reported. A comparison between international consensus diagnostic criteria for Pitt-Hopkins syndrome (PTHS) and twins presenting with NRXN1-related disorder and followed by this institution were also presented.

Results

Our data confirmed that NRXN1-related disorders mainly manifest with undistinctive dysmorphic features and neurological involvement consisting of more or less severe developmental delay/intellectual disability, autistic spectrum disorder, and epilepsy. Relationship between PTHSL2 and NRXN1 remains to be established.

Conclusions

Our present analysis denoted a heterogeneous and unspecific clinical framework of the NRXN1-related disorders mainly affecting the nervous system for which the clinical diagnosis remains inconclusive without the support of genetic analysis. Further contributions are necessary to better clarify the clinical assessment of PTHSL2.

Broadening the PHIP-Associated Neurodevelopmental Phenotype

BACKGROUND

Monoallelic damaging variants in PHIP (MIM*612870), encoding the Pleckstrin Homology Domain Interacting Protein, have been associated with a novel neurodevelopmental disorder, also termed Chung-Jansen syndrome (CHUJANS, MIM#617991). Most of the described individuals show developmental delay (DD)/intellectual disability (ID), obesity/overweight, and variable congenital anomalies, so the condition can be considered as an ID-overweight syndrome.

CASE DESCRIPTION

We evaluated a child presenting with DD/ID and a craniofacial phenotype reminiscent of a Pitt-Hopkins syndrome (PTHS)-like condition. We performed a clinical exome analysis on his biological sample, as well as an in silico prediction of the obtained data. At the same time, we interrogated the DeepGestalt technology powered by Face2Gene (F2G), using a frontal image of the proband, and clinically reviewed the earlier CHUJANS patients. In this child, we found a novel PHIP pathogenetic variant, which we corroborated through a protein modeling approach. The F2G platform supported the initial clinical hypothesis of a PTHS-like condition, while the clinical review highlighted the lack of the main frequent CHUJANS clinical features in this child.

CONCLUSIONS

The unusual clinical presentation of this novel patient resembles a PTHS-like condition. However, a novel variant in PHIP has been unexpectedly detected, expanding the phenotypic spectrum of CHUJANS. Notably, PTHS (MIM#610954), which is a different ID syndrome caused by heterozygous variants in TCF4 (MIM*610954), is not classically considered in the differential diagnosis of CHUJANS nor has been cited in the previous studies. This could support other complex diagnoses and invite further patients' descriptions.

BCL11A intellectual developmental disorder: defining the clinical spectrum and genotype-phenotype correlations

An increasing number of individuals with intellectual developmental disorder (IDD) and heterozygous variants in BCL11A are identified, yet our knowledge of manifestations and mutational spectrum is lacking. To address this, we performed detailed analysis of 42 individuals with BCL11A-related IDD (BCL11A-IDD, a.k.a. Dias-Logan syndrome) ascertained through an international collaborative network, and reviewed 35 additional previously reported patients. Analysis of 77 affected individuals identified 60 unique disease-causing variants (30 frameshift, 7 missense, 6 splice-site, 17 stop-gain) and 8 unique BCL11A microdeletions. We define the most prevalent features of BCL11A-IDD: IDD, postnatal-onset microcephaly, hypotonia, behavioral abnormalities, autism spectrum disorder, and persistence of fetal hemoglobin (HbF), and identify autonomic dysregulation as new feature. BCL11A-IDD is distinguished from 2p16 microdeletion syndrome, which has a higher incidence of congenital anomalies. Our results underscore BCL11A as an important transcription factor in human hindbrain development, identifying a previously underrecognized phenotype of a small brainstem with a reduced pons/medulla ratio. Genotype-phenotype correlation revealed an isoform-dependent trend in severity of truncating variants: those affecting all isoforms are associated with higher frequency of hypotonia, and those affecting the long (BCL11A-L) and extra-long (-XL) isoforms, sparing the short (-S), are associated with higher frequency of postnatal microcephaly. With the largest international cohort to date, this study highlights persistence of fetal hemoglobin as a consistent biomarker and hindbrain abnormalities as a common feature. It contributes significantly to our understanding of BCL11A-IDD through an extensive unbiased multi-center assessment, providing valuable insights for diagnosis, management and counselling, and into BCL11A's role in brain development.

A novel variant in the 3' UTR of the TCF4 gene likely causes Pitt-Hopkins syndrome: a case report

BACKGROUND

Pitt-Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder that results from variants of TCF4 gene. PTHS follows an autosomal dominant inheritance pattern and the underlying pathological mechanisms of this disease are still unclear.

METHODS

Whole-genome sequencing (WGS) was conducted to screen for potential pathogenic variant in a boy highly suspected of having a genetic disorder. PCR and Sanger sequencing were used to verify the effects of the variant. Serum TCF4 levels were measured by ELISA.

RESULTS

We present a 4-year and 3-month-old Chinese boy clinically and molecularly diagnosed with PTHS. The proband experienced global development delay, and the preliminary clinical diagnosis was cerebral palsy. WGS identified a de novo heterozygous variant: c.*1A > G in the 3'UTR of the TCF4 gene as a potential cause of his condition. The variant was verified to cause aberrant mRNA splicing by PCR and the aberrant splicing was confirmed by Sanger sequencing.

CONCLUSION

The study identified and demonstrated the pathogenicity of a novel 3'UTR site TCF4 variant for the first time. This research enhances understanding of pathogenetic mechanisms of PTHS and aids genetic counseling and diagnosis.

DNA methylation episignature and comparative epigenomic profiling for Pitt-Hopkins syndrome caused by TCF4 variants

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by pathogenic variants in TCF4, leading to intellectual disability, specific morphological features, and autonomic nervous system dysfunction. Epigenetic dysregulation has been implicated in PTHS, prompting the investigation of a DNA methylation (DNAm) "episignature" specific to PTHS for diagnostic purposes and variant reclassification and functional insights into the molecular pathophysiology of this disorder. A cohort of 67 individuals with genetically confirmed PTHS and three individuals with intellectual disability and a variant of uncertain significance (VUS) in TCF4 were studied. The DNAm episignature was developed with an Infinium Methylation EPIC BeadChip array analysis using peripheral blood cells. Support vector machine (SVM) modeling and clustering methods were employed to generate a DNAm classifier for PTHS. Validation was extended to an additional cohort of 11 individuals with PTHS. The episignature was assessed in relation to other neurodevelopmental disorders and its specificity was examined. A specific DNAm episignature for PTHS was established. The classifier exhibited high sensitivity for TCF4 haploinsufficiency and missense variants in the basic-helix-loop-helix domain. Notably, seven individuals with TCF4 variants exhibited negative episignatures, suggesting complexities related to mosaicism, genetic factors, and environmental influences. The episignature displayed degrees of overlap with other related disorders and biological pathways. This study defines a DNAm episignature for TCF4-related PTHS, enabling improved diagnostic accuracy and VUS reclassification. The finding that some cases scored negatively underscores the potential for multiple or nested episignatures and emphasizes the need for continued investigation to enhance specificity and coverage across PTHS-related variants.

Do Hospitals Satisfy Our Healthcare Information Needs for Rare Diseases?: Comparison of Healthcare Information Provided by Hospitals with Information Needs of Family Caregivers

This study uses a cross-sectional online survey approach to investigate the gap between healthcare information provided by hospitals and family caregivers' information needs and the relationship between demographic factors and information satisfaction. The results indicate that family caregivers have diverse healthcare information needs for daily care, but the information provided by hospitals could not satisfy these information needs most of the time. Family caregivers' information satisfaction was unrelated to various demographic factors, such as age, race, education level, and annual household income. Family caregivers who were male and spent less time searching for rare disease related information and whose children received a rare disease clinical diagnosis and spent more days in hospitals after birth expressed higher information satisfaction. Based on the findings, this study recommends strengthening continuing education of physicians about rare diseases to increase diagnosis and conducting information literacy assessments of family caregivers to better meet their information needs about daily care.

Tcf4 dysfunction alters dorsal and ventral cortical neurogenesis in Pitt-Hopkins syndrome mouse model showing sexual dimorphism

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by haploinsufficiency of transcription factor 4 (TCF4). In this work, we focused on the cerebral cortex and investigated in detail the progenitor cell dynamics and the outcome of neurogenesis in a PTHS mouse model. Labeling and quantification of progenitors and newly generated neurons at various time points during embryonic development revealed alterations affecting the dynamic of cortical progenitors since the earliest stages of cortex formation in PTHS mice. Consequently, establishment of neuronal populations and layering of the cortex were found to be altered in heterozygotes subjects at birth. Interestingly, defective layering process of pyramidal neurons was partially rescued by reintroducing TCF4 expression using focal in utero electroporation in the cerebral cortex. Coincidentally with a defective dorsal neurogenesis, we found that ventral generation of interneurons was also defective in this model, which may lead to an excitation/inhibition imbalance in PTHS. Overall, sex-dependent differences were detected with more marked effects evidenced in males compared with females. All of this contributes to expand our understanding of PTHS, paralleling the advances of research in autism spectrum disorder and further validating the PTHS mouse model as an important tool to advance preclinical studies.

Expanding the phenotype in Pitt-Hopkins syndrome; description of new oral finding and dental management considerations

BACKGROUND

Pitt-Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder with physical, cognitive, and behavioral characteristics that is caused by heterozygous mutations in the TCF4 gene. Patients with PTHS might present a unique challenge for oral healthcare professionals because of the associated comorbidities.

CASE REPORT

Here we describe a new case of PTHS in a 13-year-old girl with particular emphasis on oro-dental findings and oral healthcare management. Observed oro-dental findings in our case included shallow palate, absence of lingual frenum, gingival enlargement, thick lips and relative microdontia. The patient was unable to tolerate dental care under local anesthesia. Therefore, comprehensive dental treatment was performed under general anesthesia after a careful pre-anesthetic cardio-respiratory, neurological, and hematological evaluation. The patient was closely monitored intra-operatively for breathing rhythm, O2 saturation, and signs of respiratory distress. The patient was observed for 24 h post-op for respiratory distress and was discharged then uneventfully.

CONCLUSION

Dental treatment under general anesthesia in these patients might be complicated by the abnormal breathing rhythm, and close monitoring and follow up for signs of respiratory distress after general anesthesia is necessary. Recognition of oral and dental findings might help to expand the phenotype and better characterize rare syndromes.

From Genotype to Phenotype of Polish Patients with Pitt-Hopkins Syndrome concerning the Quality of Life and Family Functioning

Background: Pitt-Hopkins syndrome (PTHS) is a rare genetic disorder affecting psychomotor, social, and intellectual development, caused by a mutation in the TCF4 gene. The study aims to gather the phenotype and genotype data of PTHS patients from Poland and to assess the quality of life (QoL) and the impact of the disorders on the family. Methods: Eight families with PTHS participated in the study. To obtain data, the following standardized questionnaires were used: Questionnaire on Clinical Problems (QCP), the PedsQL™ Family Impact Module, and the QL-Disability Questionnaire. Additionally, a retrospective analysis of clinical examination, genetic consult, medical history, and genotype of each individual was performed. Results: All of the examined children exhibited a mutation in the TCF4 gene and typical features of PTHS. The most prevalent clinical symptoms in the study group included typical PTHS appearance, intellectual disability (n = 5; as the rest of the patients were too young to be assessed), abnormal speech development (n = 8), reduced pain response (n = 7), constipation (n = 7), drooling (n = 7), cold extremities (n = 7), and disturbances in sensory integration processes (n = 7). The QL-Disability Questionnaire revealed a total QoL score of 67.7/100 for children with PTHS, while the QoL for their families in the PedsQL Family Impact Module was 53.82/100. The highest-rated domain was cognitive functioning (Median (Me) = 67.50; Standard Deviation (SD) = 21.95), while the lowest was daily activities (Me = 25.00; SD = 29.86). Conclusions: The study allowed the collection of data on the phenotype and genotype of children with PTHS living in Poland. Overall, our study showed that the QoL of children with PTHS is impaired.

A patient with Pitt-Hopkins syndrome with concomitant common variable immunodeficiency

In patients with 18q deletion syndrome (18q-), immunodeficiency, autoimmunity, and allergies have been described in a subset. Pitt-Hopkins syndrome represents a specific subset of patients with 18q- who have a proximal deletion involving the TCF4 gene or a TCF4 variant. Immunodeficiency has been reported in the overall 18q- population; however, immunodeficiency with Pitt-Hopkins syndrome has not been highlighted. This case report details the immunologic evaluations and the associated infections seen in a young adult with Pitt-Hopkins syndrome to underscore the challenges of managing adults with a complex phenotype who develop frequent infections. This patient with Pitt-Hopkins syndrome ultimately fulfilled the diagnostic criteria for common variable immunodeficiency. Immunoglobulin replacement has led to a somewhat improved infection pattern, although she continues to have aspiration events leading to pneumonia. This case highlights the clinical evolution of Pitt-Hopkins syndrome and serves as a reminder that immunodeficiency can occur in this syndrome.

MIR137 polygenic risk for schizophrenia and ephrin-regulated pathway: Role in lateral ventricles and corpus callosum volume

Background/Objective. Enlarged lateral ventricle (LV) volume and decreased volume in the corpus callosum (CC) are hallmarks of schizophrenia (SZ). We previously showed an inverse correlation between LV and CC volumes in SZ, with global functioning decreasing with increased LV volume. This study investigates the relationship between LV volume, CC abnormalities, and the microRNA MIR137 and its regulated genes in SZ, because of MIR137's essential role in neurodevelopment. Methods. Participants were 1224 SZ probands and 1466 unaffected controls from the GENUS Consortium. Brain MRI scans, genotype, and clinical data were harmonized across cohorts and employed in the analyses. Results. Increased LV volumes and decreased CC central, mid-anterior, and mid-posterior volumes were observed in SZ probands. The MIR137-regulated ephrin pathway was significantly associated with CC:LV ratio, explaining a significant proportion (3.42 %) of CC:LV variance, and more than for LV and CC separately. Other pathways explained variance in either CC or LV, but not both. CC:LV ratio was also positively correlated with Global Assessment of Functioning, supporting previous subsample findings. SNP-based heritability estimates were higher for CC central:LV ratio (0.79) compared to CC or LV separately. Discussion. Our results indicate that the CC:LV ratio is highly heritable, influenced in part by variation in the MIR137-regulated ephrin pathway. Findings suggest that the CC:LV ratio may be a risk indicator in SZ that correlates with global functioning.

Improving care for rare genetic neurodevelopmental disorders: A systematic review and critical appraisal of clinical practice guidelines using AGREE II

PURPOSE

Rare genetic neurodevelopmental disorders associated with intellectual disability require lifelong multidisciplinary care. Clinical practice guidelines may support healthcare professionals in their daily practice, but guideline development for rare conditions can be challenging. In this systematic review, the characteristics and methodological quality of internationally published recommendations for this population are described to provide an overview of current guidelines and inform future efforts of European Reference Network ITHACA (Intellectual disability, TeleHealth, Autism, and Congenital Anomalies).

METHODS

MEDLINE, Embase, and Orphanet were systematically searched to identify guidelines for conditions classified as "rare genetic intellectual disability" (ORPHA:183757). Methodological quality was assessed using the Appraisal of Guidelines, Research, and Evaluation II tool.

RESULTS

Seventy internationally published guidelines, addressing the diagnosis and/or management of 28 conditions, were included. The methodological rigor of development was highly variable with limited reporting of literature searches and consensus methods. Stakeholder involvement and editorial independence varied as well. Implementation was rarely addressed.

CONCLUSION

Comprehensive, high-quality guidelines are lacking for many rare genetic neurodevelopmental disorders. Use and transparent reporting of sound development methodologies, active involvement of affected individuals and families, robust conflict of interest procedures, and attention to implementation are vital for enhancing the impact of clinical practice recommendations.

Autism spectrum disorders and the gastrointestinal tract: insights into mechanisms and clinical relevance

Autism spectrum disorders (ASDs) are recognized as central neurodevelopmental disorders diagnosed by impairments in social interactions, communication and repetitive behaviours. The recognition of ASD as a central nervous system (CNS)-mediated neurobehavioural disorder has led most of the research in ASD to be focused on the CNS. However, gastrointestinal function is also likely to be affected owing to the neural mechanistic nature of ASD and the nervous system in the gastrointestinal tract (enteric nervous system). Thus, it is unsurprising that gastrointestinal disorders, particularly constipation, diarrhoea and abdominal pain, are highly comorbid in individuals with ASD. Gastrointestinal problems have also been repeatedly associated with increased severity of the core symptoms diagnostic of ASD and other centrally mediated comorbid conditions, including psychiatric issues, irritability, rigid-compulsive behaviours and aggression. Despite the high prevalence of gastrointestinal dysfunction in ASD and its associated behavioural comorbidities, the specific links between these two conditions have not been clearly delineated, and current data linking ASD to gastrointestinal dysfunction have not been extensively reviewed. This Review outlines the established and emerging clinical and preclinical evidence that emphasizes the gut as a novel mechanistic and potential therapeutic target for individuals with ASD.

Complex visceral hyperalgesia in an adolescent with Pitt-Hopkins syndrome

An early-adolescent boy with a background of Pitt-Hopkins syndrome was transferred to a tertiary paediatric hospital with symptoms of a functional large bowel obstruction. He required extensive surgical intervention including a transverse colectomy, drainage of an abdominal abscess, laparotomy and adhesionolysis, and insertion of a gastrostomy and jejunostomy. He had significant ongoing issues with visceral hyperalgesia that was refractory to a wide range of pharmacological treatments and required admission to the intensive care unit on multiple occasions, and consultations with international experts in Pitt-Hopkins syndrome and pain specialists. An individualised pain plan was created and adjusted over time, with eventual good effect, and he was transferred back to his regional hospital and subsequently discharged home.

Clinical and genetic characterization of 47 Chinese pediatric patients with Pitt-Hopkins syndrome: a retrospective study

BACKGROUND

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder that remains underdiagnosed and its clinical presentations and mutation profiles in a diverse population are yet to be evaluated. This retrospective study aims to investigate the clinical and genetic characteristics of Chinese patients with PTHS.

METHODS

The clinical, biochemical, genetic, therapeutic, and follow-up data of 47 pediatric patients diagnosed with PTHS between 2018 and 2021 were retrospectively analyzed.

RESULTS

The Chinese PTHS patients presented with specific facial features and exhibited global developmental delay of wide severity range. The locus heterogeneity of the TCF4 gene in the patients was highlighted, emphasizing the significance of genetic studies for accurate diagnosis, albeit no significant correlations between genotype and phenotype were observed in this cohort. The study also reports the outcomes of patients who underwent therapeutic interventions, such as ketogenic diets and biomedical interventions.

CONCLUSIONS

The findings of this retrospective analysis expand the phenotypic and molecular spectra of PTHS patients. The study underscores the need for a long-term prospective follow-up study to assess potential therapeutic interventions.

Complex Craniosynostosis in Pitt-Hopkins Syndrome: Case Report in Twins

INTRODUCTION

Pitt-Hopkins syndrome (PTHS) is a rare genetic syndrome associated with neurodevelopmental disorders and craniofacial dysmorphisms caused by variations in the TCF4 transition factor. The aim of this article was to report the case of two twin infants diagnosed with PTHS, confirmed by the identification of a heterozygous pathogenic variant in the TCF4 gene through DNA extracted from a buccal swab.

CASE PRESENTATION

Both infants presented with craniofacial asymmetry with a metopic crest and cranial deformity. During the diagnostic investigation, computed tomography with three-dimensional reconstruction of the skull showed premature fusion of the left coronal and metopic sutures in both twins. They underwent craniofacial reconstruction at the 9th month of age using a combination of techniques. The postoperative outcomes were satisfactory in both cases.

CONCLUSION

To the best of our knowledge, this is the first case report to describe the occurrence of complex craniosynostosis (CCS) in children with PTHS. Further studies are needed to determine whether the co-occurrence of PTHS and CCS described here indicates an association or is explained by chance.

Pathogenic variants in SOX11 mimicking Pitt-Hopkins syndrome phenotype

Pitt-Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder characterised by severe intellectual disability (ID), distinctive facial features and autonomic nervous system dysfunction, caused by TCF4 haploinsufficiency. We clinically diagnosed with PTHS a 14 6/12 -year-old female, who had a normal status of TCF4. The pathogenic c.667del (p.Asp223MetfsTer45) variant in SOX11 was identified through whole exome sequencing (WES). SOX11 variants were initially reported to cause Coffin-Siris syndrome (CSS), characterised by growth restriction, moderate ID, coarse face, hypertrichosis and hypoplastic nails. However, recent studies have provided evidence that they give rise to a distinct neurodevelopmental disorder. To date, SOX11 variants are associated with a variable phenotype, which has been described to resemble CSS in some cases, but never PTHS. By reviewing both clinically and genetically 32 out of 82 subjects reported in the literature with SOX11 variants, for whom detailed information are provided, we found that 7/32 (22%) had a clinical presentation overlapping PTHS. Furthermore, we made a confirmation that overall SOX11 abnormalities feature a distinctive disorder characterised by severe ID, high incidence of microcephaly and low frequency of congenital malformations. Purpose of the present report is to enhance the role of clinical genetics in assessing the individual diagnosis after WES results.

Psychiatric risk gene Transcription Factor 4 (TCF4) regulates the density and connectivity of distinct inhibitory interneuron subtypes

Transcription factor 4 (TCF4) is a basic helix-loop-helix transcription factor that is implicated in a variety of psychiatric disorders including autism spectrum disorder (ASD), major depression, and schizophrenia. Autosomal dominant mutations in TCF4 are causal for a specific ASD called Pitt-Hopkins Syndrome (PTHS). However, our understanding of etiological and pathophysiological mechanisms downstream of TCF4 mutations is incomplete. Single cell sequencing indicates TCF4 is highly expressed in GABAergic interneurons (INs). Here, we performed cell-type specific expression analysis (CSEA) and cellular deconvolution (CD) on bulk RNA sequencing data from 5 different PTHS mouse models. Using CSEA we observed differentially expressed genes (DEGs) were enriched in parvalbumin expressing (PV+) INs and CD predicted a reduction in the PV+ INs population. Therefore, we investigated the role of TCF4 in regulating the development and function of INs in the Tcf4+/tr mouse model of PTHS. In Tcf4+/tr mice, immunohistochemical (IHC) analysis of subtype-specific IN markers and reporter mice identified reductions in PV+, vasoactive intestinal peptide (VIP+), and cortistatin (CST+) expressing INs in the cortex and cholinergic (ChAT+) INs in the striatum, with the somatostatin (SST+) IN population being spared. The reduction of these specific IN populations led to cell-type specific alterations in the balance of excitatory and inhibitory inputs onto PV+ and VIP+ INs and excitatory pyramidal neurons within the cortex. These data indicate TCF4 is a critical regulator of the development of specific subsets of INs and highlight the inhibitory network as an important source of pathophysiology in PTHS.

Unusual Inconsolable Crying: An Insight, Case Report, and Review of the Literature on the Pitt-Hopkins Gastrointestinal Phenotype

Pitt-Hopkins syndrome (PTHS) is a rare, neurodevelopmental genetic disorder caused by mutations in the TCF4 gene. This gene encodes a ubiquitous, class I, basic helix-loop-helix factor, which is implicated in various developmental and regulatory processes. Predominant clinical manifestations of PTHS include facial dysmorphisms, intellectual disability, absence of expressive language, epilepsy, as well as visual and musculoskeletal impairments. Gastrointestinal (GI) complications, such as chronic intestinal pseudo-obstruction, gastroparesis with delayed bowel transit, chronic constipation culminating in failure to thrive, and gastroesophageal reflux disease (GERD), are also prevalent in these patients. The early identification of pain etiology in PTHS patients poses a significant clinical challenge. This report presents two cases of PTHS patients suffering from gastrointestinal dysmotility, evaluated at our Pediatrics Clinic at the "Microcitemico" Hospital. A review of existing literature was conducted via the PubMed database to elucidate the current understanding of the GI phenotype in PTHS. Twenty articles were deemed most relevant and selected for this purpose. In both patients, severe constipation and abdominal distension resulted in persistent agitation and inconsolable crying. These distress symptoms were completely ameliorated following prompt pharmacological intervention.

A case of Pitt-Hopkins syndrome: psychopharmacological approach for anxiety, insomnia, and agitation

Pitt-Hopkins syndrome (PTHS) is a rare genetic disorder resulting from TCF4 gene mutations which is characterized by dysmorphic facial features, psychomotor delay, intellectual disability, breathing anomalies, and seizures. Psychiatric conditions are occasionally seen. We present the case report of a seven-year-old PTHS patient with anxiety, insomnia, and agitation. We discuss the psychopharmacological intervention options for this patient. The present case study reports on a 7-year-old female with PTHS, autism spectrum disorder (ASD), and intellectual disability. She had insomnia, crying spells and agitation complaints. For anxiety symptoms and agitation, risperidone, fluoxetine, and clonazepam treatment were given by the neurologist which caused behavioral disinhibition, paroxysmal agitation and no benefit. After admission to our hospital, aripiprazole and hydroxyzine were prescribed for anxiety and ASD-related irritability. She showed a minimal improvement but hyperventilation attacks were still ongoing. Hydroxyzine was stopped, and quetiapine was given to eliminate sleep disturbance. Her sleep period went up to eleven hours. For the anxiety symptoms, escitalopram was prescribed. She showed improvements in sleep, diminished hyperactivity and decreased frequency of abnormal breathing spells. Also, enhancement of social communication skills like increased eye contact and response to her name was observed. Patients with genetic syndromes may have various psychiatric complaints. Psychopharmacological interventions should be administered carefully for the side effects.

A typical variant in TCF4 exon 18 is not associated with Pitt-Hopkins syndrome but with a familial case of mild and nonspecific neurodevelopmental disorder

TCF4 gene encodes a class I helix-loop-helix transcription factor critical for the developing brain. Common polymorphisms in TCF4 and disruptive variants in the proximal region of the gene have been linked to relatively mild neuropsychiatric or neurodevelopmental disorders. In contrast, variants impacting distal exons are associated with Pitt-Hopkins syndrome (PTHS), a severe autosomal dominant condition characterized by profound intellectual disability, developmental delay, limited or absent speech, distinctive facies, and disordered breathing. Although phenotypic variability has been observed in PTHS, intellectual impairment and significant speech and motor delays are invariably present. In contrast to the typical de novo variants causing TCF4-related disorder and PTHS, we report a familial form of TCF4-related disorder where the missense variant arose de novo in the father and was inherited by two of his children. Although this family's variant's position in exon 18 predicted a typical PTHS phenotype, none of the affected individuals met the clinical diagnostic criteria for PTHS suggested by Zollino et al. in the first international consensus statement (as in the study by Zollino et al. in 2019). Rather, the three affected family members exhibited remarkably variable and milder phenotypes than would have been predicted from the position of their TCF4 variant. Thus, the clinical spectrum of PTHS-associated TCF4 variants may be broader than previously reported.

Consensus recommendations on organization of care for individuals with Phelan-McDermid syndrome

The manifestations of Phelan-McDermid syndrome (PMS) are complex, warranting expert and multidisciplinary care in all life stages. In the present paper we propose consensus recommendations on the organization of care for individuals with PMS. We indicate that care should consider all life domains, which can be done within the framework of the International Classification of Functioning, Disability and Health (ICF). This framework assesses disability and functioning as the outcome of the individual's interactions with other factors. The different roles within care, such as performed by a centre of expertise, by regional health care providers and by a coordinating physician are addressed. A surveillance scheme and emergency card is provided and disciplines participating in a multidisciplinary team for PMS are described. Additionally, recommendations are provided for transition from paediatric to adult care. This care proposition may also be useful for individuals with other rare genetic neurodevelopmental disorders.

A novel variant in NEUROD2 in a patient with Rett-like phenotype points to Glu130 codon as a mutational hotspot

BACKGROUND

NEUROD2, encoding the neurogenic differentiation factor 2, is essential for neurodevelopment. To date, heterozygous missense variants in this gene have been identified in eight patients (from six unrelated families) with epileptic encephalopathy and developmental delay.

CASE REPORT

We describe a child with initial clinical suspicion of Rett/Rett-like syndrome, in whom exome sequencing detected a novel de novo variant (c.388G > A, p.Glu130Lys) in NEUROD2. Interestingly, a missense change affecting the same codon, c.388G > C (p.Glu130Gln), was previously identified in other two patients.

CONCLUSIONS

Our results suggest that Glu130 might represent a potential mutational hotspot of NEUROD2. Furthermore, the clinical findings (especially the absence of clinically overt seizures) strengthen the NEUROD2-phenotypic spectrum, implying that developmental delay may also manifest isolatedly. We suggest inclusion of NEUROD2-associated developmental and epileptic encephalopathies (DEEs) in the differential diagnosis of atypical Rett syndrome as well as gene panels related to autism spectrum disorder.

Fatal gastrointestinal complications in Pitt-Hopkins syndrome

Pitt-Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder caused by mutations of the transcription factor 4 (Tcf4) gene. Individuals with PTHS often suffer from severe abdominal bloating and constipation. In this short communication, we discuss two individuals with PTHS who died unexpectedly due to gastrointestinal complications. We aim to increase awareness among healthcare professionals who care for individuals with PTHS, to ensure adequate screening and management of gastrointestinal symptoms in this population. Moreover, we discuss how fatal gastrointestinal complications may be related to PTHS and provide an overview of the literature.

Methods for Detecting Abnormal Ventilation in Children - the Case Study of 13-Years old Pitt-Hopkins Girl

We present contactless technology measuring abnormal ventilation and compare it with polysomnography (PSG). A 13-years old girl with Pitt-Hopkins syndrome presented hyperpnoea periods with apneic spells. The PSG was conducted simultaneously with Emfit movement sensor (Emfit, Finland) and video camera with depth sensor (NEL, Finland). The respiratory efforts from PSG, Emfit sensor, and NEL were compared. In addition, we measured daytime breathing with tracheal microphone (PneaVox,France). The aim was to deepen the knowledge of daytime hyperpnoea periods and ensure that no upper airway obstruction was present during sleep. The signs of upper airway obstruction were not detected despite of minor sleep time. Monitoring respiratory effort with PSG is demanding in all patient groups. The used unobtrusive methods were capable to reveal breathing frequency and hyperpnoea periods. Every day diagnostics need technology like this for monitoring vital signs at hospital wards and at home from subjects with disabilities and co-operation difficulties.

TCF4 mutations disrupt synaptic function through dysregulation of RIMBP2 in patient-derived cortical neurons

Genetic variation in the transcription factor 4 ( TCF4) gene is associated with risk for a variety of developmental and psychiatric conditions, which includes a syndromic form of ASD called Pitt Hopkins Syndrome (PTHS). TCF4 encodes an activity-dependent transcription factor that is highly expressed during cortical development and in animal models is shown to regulate various aspects of neuronal development and function. However, our understanding of how disease-causing mutations in TCF4 confer pathophysiology in a human context is lacking. Here we show that cortical neurons derived from patients with TCF4 mutations have deficits in spontaneous synaptic transmission, network excitability and homeostatic plasticity. Transcriptomic analysis indicates these phenotypes result from altered expression of genes involved in presynaptic neurotransmission and identifies the presynaptic binding protein, RIMBP2 as the most differentially expressed gene in PTHS neurons. Remarkably, TCF4-dependent deficits in spontaneous synaptic transmission and network excitability were rescued by increasing RIMBP2 expression in presynaptic neurons. Together, these results identify TCF4 as a critical transcriptional regulator of human synaptic development and plasticity and specifically identifies dysregulation of presynaptic function as an early pathophysiology in PTHS.

Difficulties in the differential diagnosis of Angelman’s syndrome

Angelman syndrome is a rare neurogenetic disease caused by the loss of the function of the maternal allele of the UBE3A gene on chromosome 15 (site 15q11.2–q13) and is characterized by severe mental retardation, lack of speech, epilepsy, microcephaly and a characteristic facial phenotype with a unique behavior in the form of frequent laughter. The combination of microcephaly, epilepsy, speechlessness and mental retardation poses a problem for differential diagnosis with many genetic diseases presenting with similar symptoms. Epileptic encephalopathy due to CDKL5 gene mutation and Rett syndrome have the greatest similarity. The hallmark of Angelman syndrome are laughter attacks and specific EEG changes. The authors have presented a table of the differential diagnosis of Angelman syndrome with some phenotypically similar genetic syndromes, indicating the most significant distinguishing features, which should facilitate for the pediatrician and neurologist the diagnostic path of establishing the correct diagnosis.

Surgical treatment of Pitt-Hopkins syndrome associated with strabismus and early-onset myopia: Two case reports

BACKGROUND

Pitt-Hopkins syndrome (PTHS; MIM #610954) is a rare genetic neurological disorder. Myopia and strabismus have been reported in approximately 50% of PTHS patients. No studies have reported details about the required surgery for PTHS with strabismus and early-onset myopia. Here, we retrospectively reviewed the surgical management of two patients with PTHS combined with strabismus and/or early-onset myopia.

CASE SUMMARY

A 5-year-old girl presented with congenital esotropia and left eye myopia, and the second girl was a 5-year-old girl who presented with intermittent exotropia. Genetic testing performed on both patients showed a mutation in transcription factor 4, which is a diagnostic marker of PTHS. The first girl underwent bilateral medial rectus recession combined with posterior scleral reinforcement (PSR) in the left eye and the second patient underwent bilateral lateral rectus recession strabismus surgery. We made key innovations in surgical timing and strategy, and the results were satisfactory. The combination of strabismus and PSR surgery is an innovative strategy for patients with both strabismus and early-onset myopia.

CONCLUSION

Early treatment of strabismus and myopia positively influence motor development and should be included in rehabilitation programs for patients with PTHS.

Expression of alternative transcription factor 4 mRNAs and protein isoforms in the developing and adult rodent and human tissues

Transcription factor 4 (TCF4) belongs to the class I basic helix-loop-helix family of transcription factors (also known as E-proteins) and is vital for the development of the nervous system. Aberrations in the TCF4 gene are associated with several neurocognitive disorders such as schizophrenia, intellectual disability, post-traumatic stress disorder, depression, and Pitt-Hopkins Syndrome, a rare but severe autism spectrum disorder. Expression of the human TCF4 gene can produce at least 18 N-terminally distinct protein isoforms, which activate transcription with different activities and thus may vary in their function during development. We used long-read RNA-sequencing and western blot analysis combined with the analysis of publicly available short-read RNA-sequencing data to describe both the mRNA and protein expression of the many distinct TCF4 isoforms in rodent and human neural and nonneural tissues. We show that TCF4 mRNA and protein expression is much higher in the rodent brain compared to nonneural tissues. TCF4 protein expression is highest in the rodent cerebral cortex and hippocampus, where expression peaks around birth, and in the rodent cerebellum, where expression peaks about a week after birth. In human, highest TCF4 expression levels were seen in the developing brain, although some nonneural tissues displayed comparable expression levels to adult brain. In addition, we show for the first time that out of the many possible TCF4 isoforms, the main TCF4 isoforms expressed in the rodent and human brain and other tissues are TCF4-B, -C, -D, -A, and-I. Taken together, our isoform specific analysis of TCF4 expression in different tissues could be used for the generation of gene therapy applications for patients with TCF4-associated diseases.

Genetics behind Cerebral Disease with Ocular Comorbidity: Finding Parallels between the Brain and Eye Molecular Pathology

Cerebral visual impairments (CVIs) is an umbrella term that categorizes miscellaneous visual defects with parallel genetic brain disorders. While the manifestations of CVIs are diverse and ambiguous, molecular diagnostics stand out as a powerful approach for understanding pathomechanisms in CVIs. Nevertheless, the characterization of CVI disease cohorts has been fragmented and lacks integration. By revisiting the genome-wide and phenome-wide association studies (GWAS and PheWAS), we clustered a handful of renowned CVIs into five ontology groups, namely ciliopathies (Joubert syndrome, Bardet-Biedl syndrome, Alstrom syndrome), demyelination diseases (multiple sclerosis, Alexander disease, Pelizaeus-Merzbacher disease), transcriptional deregulation diseases (Mowat-Wilson disease, Pitt-Hopkins disease, Rett syndrome, Cockayne syndrome, X-linked alpha-thalassaemia mental retardation), compromised peroxisome disorders (Zellweger spectrum disorder, Refsum disease), and channelopathies (neuromyelitis optica spectrum disorder), and reviewed several mutation hotspots currently found to be associated with the CVIs. Moreover, we discussed the common manifestations in the brain and the eye, and collated animal study findings to discuss plausible gene editing strategies for future CVI correction.

Molecular Organization and Patterning of the Medulla Oblongata in Health and Disease

The medulla oblongata, located in the hindbrain between the pons and the spinal cord, is an important relay center for critical sensory, proprioceptive, and motoric information. It is an evolutionarily highly conserved brain region, both structural and functional, and consists of a multitude of nuclei all involved in different aspects of basic but vital functions. Understanding the functional anatomy and developmental program of this structure can help elucidate potential role(s) of the medulla in neurological disorders. Here, we have described the early molecular patterning of the medulla during murine development, from the fundamental units that structure the very early medullary region into 5 rhombomeres (r7–r11) and 13 different longitudinal progenitor domains, to the neuronal clusters derived from these progenitors that ultimately make-up the different medullary nuclei. By doing so, we developed a schematic overview that can be used to predict the cell-fate of a progenitor group, or pinpoint the progenitor domain of origin of medullary nuclei. This schematic overview can further be used to help in the explanation of medulla-related symptoms of neurodevelopmental disorders, e.g., congenital central hypoventilation syndrome, Wold–Hirschhorn syndrome, Rett syndrome, and Pitt–Hopkins syndrome. Based on the genetic defects seen in these syndromes, we can use our model to predict which medullary nuclei might be affected, which can be used to quickly direct the research into these diseases to the likely affected nuclei.

Recommendations by the ClinGen Rett/Angelman-like expert panel for gene-specific variant interpretation methods

The genes MECP2, CDKL5, FOXG1, UBE3A, SLC9A6, and TCF4 present unique challenges for current ACMG/AMP variant interpretation guidelines. To address those challenges, the Rett and Angelman-like Disorders Variant Curation Expert Panel (Rett/AS VCEP) drafted gene-specific modifications. A pilot study was conducted to test the clarity and accuracy of using the customized variant interpretation criteria. Multiple curators obtained the same interpretation for 78 out of the 87 variants (~90%), indicating appropriate usage of the modified guidelines the majority of times by all the curators. The classification of 13 variants changed using these criteria specifications compared to when the variants were originally curated and as present in ClinVar. Many of these changes were due to internal data shared from laboratory members however some changes were because of changes in strength of criteria. There were no two-step classification changes and only 1 clinically relevant change (Likely pathogenic to VUS). The Rett/AS VCEP hopes that these gene-specific variant curation rules and the assertions provided help clinicians, clinical laboratories, and others interpret variants in these genes but also other fully penetrant, early-onset genes associated with rare disorders.

The recurrent TCF4 missense variant p.(Arg389Cys) causes a neurodevelopmental disorder overlapping with but not typical for Pitt-Hopkins syndrome

TCF4 haploinsufficiency by deletions, truncating variants or loss-of-function missense variants within the DNA-binding and protein interacting bHLH domain causes Pitt-Hopkins syndrome (PTHS). This neurodevelopmental disorder (NDD) is characterized by severe intellectual disability (ID), epilepsy, hyperbreathing and a typical facial gestalt. Only few aberrations of the N-terminus of TCF4 were associated with milder or atypical phenotypes. By personal communication and searching databases we assembled six cases with the novel, recurrent, de novo missense variant c.1165C > T, p.(Arg389Cys) in TCF4. This variant was identified by diagnostic exome or panel sequencing and is located upstream of the bHLH domain. All six individuals presented with moderate to severe ID with language impairment. Microcephaly occurred in two individuals, epilepsy only in one, and no breathing anomalies or myopia were reported. Facial gestalt showed some aspects of PTHS but was rather non-specific in most individuals. Interestingly, the variant is located within the AD2 activation domain next to a highly conserved coactivator-recruitment motif and might alter interaction with coactivator proteins independently from the bHLH domain. Our findings of a recurrent missense variant outside the bHLH domain in six individuals with an ID phenotype overlapping with but not typical for PTHS delineate a novel genotype-phenotype correlation for TCF4-related NDDs. This article is protected by copyright. All rights reserved.

Accelerating the genetic diagnosis of neurological disorders presenting with episodic apnoea in infancy

Unexplained episodic apnoea in infants (aged ≤1 year), including recurrent brief (<1 min) resolved unexplained events (known as BRUE), can be a diagnostic challenge. Recurrent unexplained apnoea might suggest a persistent, debilitating, and potentially fatal disorder. Genetic diseases are prevalent among this group, particularly in those who present with paroxysmal or episodic neurological symptoms. These disorders are individually rare and challenging for a general paediatrician to recognise, and there is often a delayed or even posthumous diagnosis (sometimes only made in retrospect when a second sibling becomes unwell). The disorders can be debilitating if untreated but pharmacotherapies are available for the vast majority. That any child should suffer from unnecessary morbidity or die from one of these disorders without a diagnosis or treatment having been offered is a tragedy; therefore, there is an urgent need to simplify and expedite the diagnostic journey. We propose an apnoea gene panel for hospital specialists caring for any infant who has recurrent apnoea without an obvious cause. This approach could remove the need to identify individual rare conditions, speed up diagnosis, and improve access to therapy, with the ultimate aim of reducing morbidity and mortality.

Pitt-Hopkins syndrome accompanying hypoxic ischemic encephalopathy in a newborn

Hypoxic-ischemic encephalopathy (HIE) is one of the substantial causes of developmental-cognitive disability in neonates. In this early period, it is difficult to diagnose accompanying or predisposing genetic diseases in HIE patients. Herein, we present a patient with HIE who was diagnosed with Pitt-Hopkins syndrome in the newborn period.

Rescue of behavioral and electrophysiological phenotypes in a Pitt-Hopkins syndrome mouse model by genetic restoration of Tcf4 expression

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by monoallelic mutation or deletion in the transcription factor 4 (TCF4) gene. Individuals with PTHS typically present in the first year of life with developmental delay and exhibit intellectual disability, lack of speech, and motor incoordination. There are no effective treatments available for PTHS, but the root cause of the disorder, TCF4 haploinsufficiency, suggests that it could be treated by normalizing TCF4 gene expression. Here, we performed proof-of-concept viral gene therapy experiments using a conditional Tcf4 mouse model of PTHS and found that postnatally reinstating Tcf4 expression in neurons improved anxiety-like behavior, activity levels, innate behaviors, and memory. Postnatal reinstatement also partially corrected EEG abnormalities, which we characterized here for the first time, and the expression of key TCF4-regulated genes. Our results support a genetic normalization approach as a treatment strategy for PTHS, and possibly other TCF4-linked disorders.

Transcription Factor 4 loss-of-function is associated with deficits in progenitor proliferation and cortical neuron content

Transcription Factor 4 (TCF4) has been associated with autism, schizophrenia, and other neuropsychiatric disorders. However, how pathological TCF4 mutations affect the human neural tissue is poorly understood. Here, we derive neural progenitor cells, neurons, and brain organoids from skin fibroblasts obtained from children with Pitt-Hopkins Syndrome carrying clinically relevant mutations in TCF4. We show that neural progenitors bearing these mutations have reduced proliferation and impaired capacity to differentiate into neurons. We identify a mechanism through which TCF4 loss-of-function leads to decreased Wnt signaling and then to diminished expression of SOX genes, culminating in reduced progenitor proliferation in vitro. Moreover, we show reduced cortical neuron content and impaired electrical activity in the patient-derived organoids, phenotypes that were rescued after correction of TCF4 expression or by pharmacological modulation of Wnt signaling. This work delineates pathological mechanisms in neural cells harboring TCF4 mutations and provides a potential target for therapeutic strategies for genetic disorders associated with this gene.

Two types of early epileptic encephalopathy in a Pitt-Hopkins syndrome patient with a novel TCF4 mutation

INTRODUCTION

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by mutations in TCF4. Seizures have been found to vary among patients with PTHS. We report the case of a PTHS patient with a novel missense mutation in the gene TCF4, presenting with two types of early epileptic encephalopathy.

CASE REPORT

The patient was a Japanese boy. His first seizure was reported at 17 days of age, with twitching of the left eyelid and tonic-clonic seizures on either side of his body. An ictal electroencephalogram (EEG) showed epileptic discharges arising independently from both hemispheres, occasionally resembling migrating partial seizures of infancy (MPSI) that migrated from one side to the other. Brain magnetic resonance imaging revealed agenesis of the corpus callosum. His facial characteristics included a distinctive upper lip and thickened helices. His seizures were refractory, and psychomotor development was severely delayed. At the age of 10 months, he developed West syndrome with spasms and hypsarrhythmia. After being prescribed topiramate (TPM), his seizures and EEG abnormalities dramatically improved. Also, psychomotor development progressed. Whole-exome sequencing revealed a novel de novo missense mutation in exon 18 (NM_001083962.2:c.1718A > T, p.(Asn573Ile)), corresponding to the basic region of the basic helix-loop-helix domain, which may be a causative gene for epileptic encephalopathy.

CONCLUSIONS

To our knowledge, this is the first report of a patient with PTHS treated with TPM, who presented with both MPSI as well as West syndrome. This may help provide new insights regarding the phenotypes caused by mutations in TCF4.

Functional consequences of TCF4 missense substitutions associated with Pitt-Hopkins syndrome, mild intellectual disability, and schizophrenia

Transcription factor 4 (TCF4) is a basic helix-loop-helix transcription factor essential for neurocognitive development. The aberrations in TCF4 are associated with neurodevelopmental disorders including schizophrenia, intellectual disability, and Pitt-Hopkins syndrome, an autism-spectrum disorder characterized by developmental delay. Several disease-associated missense mutations in TCF4 have been shown to interfere with TCF4 function, but for many mutations, the impact remains undefined. Here, we tested the effects of 12 functionally uncharacterized disease-associated missense mutations and variations in TCF4 using transient expression in mammalian cells, confocal imaging, in vitro DNA-binding assays, and reporter assays. We show that Pitt-Hopkins syndrome-associated missense mutations within the basic helix-loop-helix domain of TCF4 and a Rett-like syndrome-associated mutation in a transcription activation domain result in altered DNA-binding and transcriptional activity of the protein. Some of the missense variations found in schizophrenia patients slightly increase TCF4 transcriptional activity, whereas no effects were detected for missense mutations linked to mild intellectual disability. We in addition find that the outcomes of several disease-related mutations are affected by cell type, TCF4 isoform, and dimerization partner, suggesting that the effects of TCF4 mutations are context-dependent. Together with previous work, this study provides a basis for the interpretation of the functional consequences of TCF4 missense variants.

Disordered breathing in a Pitt-Hopkins syndrome model involves Phox2b-expressing parafacial neurons and aberrant Nav1.8 expression

Pitt-Hopkins syndrome (PTHS) is a rare autism spectrum-like disorder characterized by intellectual disability, developmental delays, and breathing problems involving episodes of hyperventilation followed by apnea. PTHS is caused by functional haploinsufficiency of the gene encoding transcription factor 4 (Tcf4). Despite the severity of this disease, mechanisms contributing to PTHS behavioral abnormalities are not well understood. Here, we show that a Tcf4 truncation (Tcf4^tr/+) mouse model of PTHS exhibits breathing problems similar to PTHS patients. This behavioral deficit is associated with selective loss of putative expiratory parafacial neurons and compromised function of neurons in the retrotrapezoid nucleus that regulate breathing in response to tissue CO₂/H⁺. We also show that central Nav1.8 channels can be targeted pharmacologically to improve respiratory function at the cellular and behavioral levels in Tcf4^tr/+ mice, thus establishing Nav1.8 as a high priority target with therapeutic potential in PTHS.

Disordered breathing is a hallmark of Pitt-Hopkins syndrome (PTHS), yet little is known regarding how loss of Tcf4 (gene associated with PTHS) affects development and function of respiratory neurons. Here, the authors show that parafacial respiratory neurons are selectively disrupted in a mouse model of PTHS, and central Nav1.8 channels can be targeted to improve PTHS-associated behavior abnormalities.

Epilepsy, electroclinical features, and long-term outcomes in Pitt-Hopkins syndrome due to pathogenic variants in the TCF4 gene

BACKGROUND AND PURPOSE

Pitt-Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder caused by deletions/variants in the TCF4 gene. Seizures may be present in up to half of the patients, leading to a more severe disease burden. This study aims to analyse the electroclinical phenotype, treatment options, and long-term outcomes of epilepsy in PTHS.

METHODS

A multicentre observational cohort study was performed, and the electroclinical data of PTHS individuals affected by epileptic seizures were retrospectively reviewed and analysed.

RESULTS

The series includes 21 patients (11 female) with a median age at seizure onset of 2 years (range = 0.5-8). The median time of follow-up was 7.9 years (range = 2-27). Both generalized and focal epilepsies were present at the same prevalence (42.8%), whereas a minority of patients presented developmental and epileptic encephalopathies (14.4%). At the long-term follow-up, 42.8% achieved seizure freedom, whereas 42.8% developed drug-resistant epilepsy (DRE). The age at seizure onset was found to be an independent predictor for seizure outcome; in this regard, patients having seizure onset after the age of 2 years were more prone to achieve seizure freedom (odds ratio = 0.04, 95% confidence interval = 0.003-0.53; p = 0.01). During evolution, seizures tended to settle down, and even in patients with DRE, seizures tended to persist at a lower frequency and appeared to be more easily manageable over time.

CONCLUSIONS

This study provides new insight into the natural history of epilepsy in PTHS. Better characterization of epileptic phenotype and prompt tailored treatment improve overall management and quality of life.

Molecular and Cellular Function of Transcription Factor 4 in Pitt-Hopkins Syndrome

Transcription factor 4 (TCF4, also known as ITF2 or E2-2) is a type I basic helix-loop-helix transcription factor. Autosomal dominant mutations in TCF4 cause Pitt-Hopkins syndrome (PTHS), a rare syndromic form of autism spectrum disorder. In this review, we provide an update on the progress regarding our understanding of TCF4 function at the molecular, cellular, physiological, and behavioral levels with a focus on phenotypes and therapeutic interventions. We examine upstream and downstream regulatory networks associated with TCF4 and discuss a range of in vitro and in vivo data with the aim of understanding emerging TCF4-specific mechanisms relevant for disease pathophysiology. In conclusion, we provide comments about exciting future avenues of research that may provide insights into potential new therapeutic targets for PTHS.

Pitt-Hopkins syndrome: phenotypic and genotypic description of four unrelated patients and structural analysis of corresponding missense mutations

Pitt-Hopkins syndrome is an underdiagnosed neurodevelopmental disorder which is characterized by specific facial features, early-onset developmental delay, and moderate to severe intellectual disability. The genetic cause, a deficiency of the TCF4 gene, has been established; however, the underlying pathological mechanisms of this disease are still unclear. Herein, we report four unrelated children with different de novo mutations (T606A, K607E, R578C, and V617I) located at highly conserved sites and with clinical phenotypes which present variable degrees of developmental delay and intellectual disability. Three of these four missense mutations have not yet been reported. The patient with V617I mutation exhibits mild intellectual disability and has attained more advanced motor and verbal skills, which is significantly different from other cases reported to date. Molecular dynamics simulations are used to explore the atomic level mechanism of how missense mutations impair the functions of TCF4. Mutations T606A, K607E, and R578C are found to affect DNA binding directly or indirectly, while V617I only induces subtle conformational changes, which is consistent with the milder clinical phenotype of the corresponding patient. The study expands the mutation spectrum and phenotypic characteristics of Pitt-Hopkins syndrome, and reinforces the genotype-phenotype correlation and strengthens the understanding of phenotype variability, which is helpful for further investigation of pathogenetic mechanisms and improved genetic counseling.

Tcf4 Is Involved in Subset Specification of Mesodiencephalic Dopaminergic Neurons

During development, mesodiencephalic dopaminergic (mdDA) neurons form into different molecular subsets. Knowledge of which factors contribute to the specification of these subsets is currently insufficient. In this study, we examined the role of Tcf4, a member of the E-box protein family, in mdDA neuronal development and subset specification. We show that Tcf4 is expressed throughout development, but is no longer detected in adult midbrain. Deletion of Tcf4 results in an initial increase in TH-expressing neurons at E11.5, but this normalizes at later embryonic stages. However, the caudal subset marker Nxph3 and rostral subset marker Ahd2 are affected at E14.5, indicating that Tcf4 is involved in correct differentiation of mdDA neuronal subsets. At P0, expression of these markers partially recovers, whereas expression of Th transcript and TH protein appears to be affected in lateral parts of the mdDA neuronal population. The initial increase in TH-expressing cells and delay in subset specification could be due to the increase in expression of the bHLH factor Ascl1, known for its role in mdDA neuronal differentiation, upon loss of Tcf4. Taken together, our data identified a minor role for Tcf4 in mdDA neuronal development and subset specification.

Transcription factor 4 and its association with psychiatric disorders

The human transcription factor 4 gene (TCF4) encodes a helix-loop-helix transcription factor widely expressed throughout the body and during neural development. Mutations in TCF4 cause a devastating autism spectrum disorder known as Pitt-Hopkins syndrome, characterized by a range of aberrant phenotypes including severe intellectual disability, absence of speech, delayed cognitive and motor development, and dysmorphic features. Moreover, polymorphisms in TCF4 have been associated with schizophrenia and other psychiatric and neurological conditions. Details about how TCF4 genetic variants are linked to these diseases and the role of TCF4 during neural development are only now beginning to emerge. Here, we provide a comprehensive review of the functions of TCF4 and its protein products at both the cellular and organismic levels, as well as a description of pathophysiological mechanisms associated with this gene.

Case report: Pitt-Hopkins like syndrome with CNTNAP2 mutation

Background

Pitt-Hopkins syndrome (PHS) is a rare cause of severe intellectual disability, seizures, language impairment, and peculiar facial dysmorphism. It is caused by a mutation in transcription factor 4 (TCF4). Through molecular karyotyping and mutational analysis, a study identified recessive defects in two genes, contactin associated protein like 2 (CNTNAP2) and Neurexin I (NRXN1), in patients with similar presentations of Pitt-Hopkins syndrome and called Pitt-Hopkins-like syndrome (Zweier et al., J Med Genet 80: 994-1001, 2007).

We present the first case report of a child in Iraq with Pitt-Hopkins-like syndrome that was referred to the Welfare Children’s Hospital/Medical City of Baghdad because of her intellectual disability.

Case presentation

The patient was 4-year-old female child who presented with psychomotor delay and language impairment. She had frequent attacks of the respiratory tract and eye infections. Ophthalmologic examination revealed left-sided esotropia and severe myopia. Routine hematologic, serologic, and chemistry tests were within normal ranges. EEG revealed diffuse theta slowing and diffuse beta activity. The audiological test was normal. NCS and EMG showed normal results. Echo study, chest X-ray, and abdominal/pelvic ultrasound revealed normal findings. Brain MRI showed mild bilateral frontal-temporal atrophy. Whole-exome sequencing (WES) revealed a homozygous stop mutation in CNTNAP2 with a heterozygous state in both parents.

Conclusion

Intellectual disability may result from different types of abnormal cellular processes and with widening the use of molecular gene analysis in cases of intellectual disability, underdiagnosed cases of Pitt-Hopkins and Pitt-Hopkins-like syndromes may be uncovered.

CDKL5 mutations may mimic Pitt-Hopkins syndrome phenotype

Genetic conditions comprise a wide spectrum of different phenotypes, rapidly expanding due to new diagnostic methodologies. Patients' facial features and clinical history represent the key elements leading clinicians to the right diagnosis. CDKL5-early onset epilepsy and Pitt-Hopkins syndrome are two well-known genetic conditions, with a defined phenotype sharing some common characteristics like early-onset epilepsy and hyperventilation episodes. Whilst facial features represent a diagnostic handle in patients with Pitt-Hopkins syndrome, clinical history is crucial in patients carrying a mutation in CDKL5. Here we present the clinical case of a girl evaluated for the first time when she was 24-years old, with a clinical phenotype mimicking Pitt-Hopkins syndrome. Her facial features have become coarser while she was growing up, leading geneticists to raise different clinical hypotheses and to perform several molecular tests before getting the diagnosis of CDKL5-early-epileptic encephalopathy. This finding highlights that although typical facial gestalt has not so far extensively been described in CDKL5 mutated adult patients, peculiar facial features could be present later in life and may let CDKL5-related disorder mimic Pitt Hopkins. Thus, considering atypical Rett syndrome in the differential diagnosis of Pitt Hopkins syndrome could be important to solve complex clinical cases.