Project description:Pitt-Hopkins syndrome (PTHS, MIM #610954) is characterized by severe intellectual disability, typical facial features and tendency to epilepsy, panting-and-holding breathing anomaly, stereotypic movements, constipation, and high myopia. Growth is normal or only mildly retarded, but half of the patients have postnatal microcephaly. Remarkably, congenital malformations are practically nonexistent. The cause of PTHS is de novo haploinsufficiency of the TCF4 gene (MIM *602272) at 18q21.2. Altogether 78 PTHS patients with abnormalities of the TCF4 gene have been published since 2007 when the etiology of PTHS was revealed. In addition, 27 patients with 18q deletion encompassing the TCF4 gene but without given PTHS diagnosis have been published, and thus, the number of reported patients with a TCF4 abnormality exceeds 100. The mutational spectrum includes large chromosomal deletions encompassing the whole TCF4 gene, partial gene deletions, frameshift (including premature stop codon), nonsense, splice site, and missense mutations. So far, almost all patients have a private mutation and only 2 recurrent mutations are known. There is no evident genotype-phenotype correlation. No familial cases have been reported. Diagnosis of PTHS is based on the molecular confirmation of the characteristic clinical features. Recently, a Pitt-Hopkins-like phenotype has been assigned to autosomal recessive mutations of the CNTNAP2 gene at 7q33q36 and the NRXN1 gene at 2p16.3.
Project description:Pitt-Hopkins syndrome is an emerging neurodevelopmental disorder caused by haploinsufficiency of the TCF4 gene on chromosome 18q21. It is characterized by severe intellectual disability, seizures, microcephaly, constipation and a distinctive facial gestalt. Although the overlapping phenotype of microcephaly, epilepsy, absent speech and constipation represents a challenge for the differential diagnosis with Angelman syndrome, Rett syndrome and Mowat-Wilson syndrome, distinctive of Pitt-Hopkins syndrome are breathing abnormalities, that can occur as either hyperventilation episodes or apnea crises, and a typical facial dysmorphism, including bitemporal narrowing, squared forehead, deep-set eyes, peculiar nose conformation, with broad nasal bridge, down-turned nasal tip and flaring nostrils, typical shape of the mouth, with a tented and M shaped upper lip, and widely spaced teeth. The occurrence of these signs in variable association of uncoordinated movements, microcephaly of postnatal onset, eye abnormalities, constipation, epilepsy and subtle brain abnormalities is highly predictive of a TCF4 mutation, making it possible to plan a genetic test of choice among severe encephalopathies. Angelman syndrome represents the nosological condition closest to Pitt-Hopkins syndrome.
Project description:Genome-wide association studies allied with the identification of rare copy number variants have provided important insights into the genetic risk factors for schizophrenia. Recently, a meta-analysis of several genome-wide association studies found, in addition to several other markers, a single nucleotide polymorphism in intron 4 of the TCF4 gene that was associated with schizophrenia. TCF4 encodes a basic helix-loop-helix transcription factor that interacts with other transcription factors to activate or repress gene expression. TCF4 mutations also cause Pitt-Hopkins Syndrome, an autosomal-dominant neurodevelopmental disorder associated with severe mental retardation. Variants in the TCF4 gene may therefore be associated with a range of neuropsychiatric phenotypes, including schizophrenia. Recessive forms of Pitt-Hopkins syndrome are caused by mutations in NRXN1 and CNTNAP2. Interestingly, NRXN1 deletions have been reported in schizophrenia, whereas CNTNAP2 variants are associated with several neuropsychiatric phenotypes. These data suggest that TCF4, NRXN1, and CNTNAP2 may participate in a biological pathway that is altered in patients with schizophrenia and other neuropsychiatric disorders.
Project description:Pitt-Hopkins syndrome is a rarely reported syndrome of so-far-unknown etiology characterized by mental retardation, wide mouth, and intermittent hyperventilation. By molecular karyotyping with GeneChip Human Mapping 100K SNP arrays, we detected a 1.2-Mb deletion on 18q21.2 in one patient. Sequencing of the TCF4 transcription factor gene, which is contained in the deletion region, in 30 patients with significant phenotypic overlap revealed heterozygous stop, splice, and missense mutations in five further patients with severe mental retardation and remarkable facial resemblance. Thus, we establish the Pitt-Hopkins syndrome as a distinct but probably heterogeneous entity caused by autosomal dominant de novo mutations in TCF4. Because of its phenotypic overlap, Pitt-Hopkins syndrome evolves as an important differential diagnosis to Angelman and Rett syndromes. Both null and missense mutations impaired the interaction of TCF4 with ASCL1 from the PHOX-RET pathway in transactivating an E box-containing reporter construct; therefore, hyperventilation and Hirschsprung disease in patients with Pitt-Hopkins syndrome might be explained by altered development of noradrenergic derivatives.
Project description:Purpose of Review:Pitt Hopkins syndrome (PTHS) is a rare neurodevelopmental disorder that results from mutations of the clinically pleiotropic Transcription Factor 4 (TCF4) gene. Mutations in the genomic locus of TCF4 on chromosome 18 have been linked to multiple disorders including 18q syndrome, schizophrenia, Fuch's corneal dystrophy, and sclerosing cholangitis. For PTHS, TCF4 mutation or deletion leads to the production of a dominant negative TCF4 protein and/or haploinsufficiency that results in abnormal brain development. The biology of TCF4 has been studied for several years in regards to its role in immune cell differentiation, although its role in neurodevelopment and the mechanisms resulting in the severe symptoms of PTHS are not well studied. Recent Findings:Here, we summarize the current understanding of PTHS and recent findings that have begun to describe the biological implications of TCF4 deficiency during brain development and into adulthood. In particular, we focus on recent work that has looked at the role of TCF4 biology within the context of PTHS and highlight the potential for identification of therapeutic targets for PTHS. Summary:PTHS research continues to uncover mutations in TCF4 that underlie the genetic cause of this rare disease, and emerging evidence for molecular mechanisms that TCF4 regulates in brain development and neuronal function is contributing to a more complete picture of how pathology arises from this genetic basis, with important implications for the potential of future clinical care.
Project description:Autosomal dominant mutations in transcription factor 4 (TCF4) are associated with a rare syndromic form of Autism Spectrum Disorder (ASD) called Pitt-Hopkins Syndrome (PTHS). Here, we report the generation of a collection of induced pluripotent stem cells (iPSCs) from 5 patients diagnosed with PTHS and 5 familial controls. These patient-derived iPSCs contain a variety of mutations within the TCF4 gene, possess a normal karyotype and express all the appropriate pluripotent stem cell markers. These novel patient lines will be a useful resource for the research community to study PTHS and the function of TCF4.
Project description:TCF4 (transcription factor 4; E2-2, ITF2) is a transcription factor that when haplo-insufficient causes Pitt-Hopkins Syndrome (PTHS), an autism-spectrum disorder that is associated with pervasive developmental delay and severe intellectual disability. The TCF4 gene is also a risk factor with highly significant linkage to schizophrenia, presumably via overexpression of the TCF4 gene product in the central nervous system. This review will present an overview of the clinical manifestations of PTHS and relate those clinical attributes to the underlying molecular genetics of TCF4. In order to provide a molecular biological context for the loss of function of TCF4 in PTHS, the review will also present a brief overview of the basic biochemistry of TCF4-mediated regulation of cellular and neuronal gene expression. In the final section of this review, I will discuss and speculate upon possible roles for the TCF4 transcription factor in neuronal function and comment upon how understanding these roles may give new insights into the molecular neurobiology of human cognition.
Project description:Pitt Hopkins syndrome (PTHS) is a very rare condition and until now, approximately 500 patients were reported worldwide, of which not all are genetically confirmed. Usually, individuals with variants affecting exons 1 to 5 in the TCF4 gene associate mild intellectual disability (ID), between exons 5 to 8, moderate to severe ID and sometimes have some of the characteristics of PTHS, and variants starting from exon 9 to exon 20 associate a typical PTHS phenotype. In this report, we describe the clinical and molecular findings of a Caucasian boy diagnosed with PTHS. PTHS phenotype is described including craniofacial dysmorphism with brachycephaly, biparietal narrowing, wide nasal bridge, thin and linear lateral eyebrows, palpebral edema, full cheeks, short philtrum, wide mouth with prominent and everted lips, prominent Cupid's bow, downturned corners of the mouth, microdontia and also the clinical management of the patient. The previously and the current diagnosis scores are described in this report and also the challenges and their benefits for an accurate and early diagnosis.