Human Genetics of Ventricular Septal Defect.

Ventricular septal defects (VSDs) are recognized as one of the commonest congenital heart diseases (CHD), accounting for up to 40% of all cardiac malformations, and occur as isolated CHDs as well as together with other cardiac and extracardiac congenital malformations in individual patients and families. The genetic etiology of VSD is complex and extraordinarily heterogeneous. Chromosomal abnormalities such as aneuploidy and structural variations as well as rare point mutations in various genes have been reported to be associated with this cardiac defect. This includes both well-defined syndromes with known genetic cause (e.g., DiGeorge syndrome and Holt-Oram syndrome) and so far undefined syndromic forms characterized by unspecific symptoms. Mutations in genes encoding cardiac transcription factors (e.g., NKX2-5 and GATA4) and signaling molecules (e.g., CFC1) have been most frequently found in VSD cases. Moreover, new high-resolution methods such as comparative genomic hybridization enabled the discovery of a high number of different copy number variations, leading to gain or loss of chromosomal regions often containing multiple genes, in patients with VSD. In this chapter, we will describe the broad genetic heterogeneity observed in VSD patients considering recent advances in this field.

Absence of Scaffold Protein Tks4 Disrupts Several Signaling Pathways in Colon Cancer Cells.

Tks4 is a large scaffold protein in the EGFR signal transduction pathway that is involved in several cellular processes, such as cellular motility, reactive oxygen species-dependent processes, and embryonic development. It is also implicated in a rare developmental disorder, Frank-ter Haar syndrome. Loss of Tks4 resulted in the induction of an EMT-like process, with increased motility and overexpression of EMT markers in colorectal carcinoma cells. In this work, we explored the broader effects of deletion of Tks4 on the gene expression pattern of HCT116 colorectal carcinoma cells by transcriptome sequencing of wild-type and Tks4 knockout (KO) cells. We identified several protein coding genes with altered mRNA levels in the Tks4 KO cell line, as well as a set of long non-coding RNAs, and confirmed these changes with quantitative PCR on a selected set of genes. Our results show a significant perturbation of gene expression upon the deletion of Tks4, suggesting the involvement of different signal transduction pathways over the well-known EGFR signaling.

A Novel Cell-Based Model for a Rare Disease: The Tks4-KO Human Embryonic Stem Cell Line as a Frank-Ter Haar Syndrome Model System.

Tyrosine kinase substrate with four SH3 domains (Tks4) scaffold protein plays roles in cell migration and podosome formation and regulates systemic mechanisms such as adult bone homeostasis and adipogenesis. Mutations in the Tks4 gene (SH3PXD2b) cause a rare developmental disorder called Frank-Ter Haar syndrome (FTHS), which leads to heart abnormalities, bone tissue defects, and reduced adiposity. We aimed to produce a human stem cell-based in vitro FTHS model system to study the effects of the loss of the Tks4 protein in different cell lineages and the accompanying effects on the cell signalome. To this end, we used CRISPR/Cas9 (clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR associated (Cas9)) to knock out the SH3PXD2b gene in the HUES9 human embryonic stem cell line (hESC), and we obtained stable homo- and heterozygous knock out clones for use in studying the potential regulatory roles of Tks4 protein in embryonic stem cell biology. Based on pluripotency marker measurements and spontaneous differentiation capacity assays, we concluded that the newly generated Tks4-KO HUES9 cells retained their embryonic stem cell characteristics. We propose that the Tks4-KO HUES9 cells could serve as a tool for further cell differentiation studies to investigate the involvement of Tks4 in the complex disorder FTHS. Moreover, we successfully differentiated all of the clones into mesenchymal stem cells (MSCs). The derived MSC cultures showed mesenchymal morphology and expressed MSC markers, although the expression levels of mesodermal and osteogenic marker genes were reduced, and several EMT (epithelial mesenchymal transition)-related features were altered in the Tks4-KO MSCs. Our results suggest that the loss of Tks4 leads to FTHS by altering cell lineage differentiation and cell maturation processes, rather than by regulating embryonic stem cell potential.

Whole exome sequencing enables the correct diagnosis of Frank-Ter Haar syndrome in a Saudi family.

Frank-Ter Haar syndrome (FTHS) is a rare genetic hereditary autosomal recessive disorder characterized by defective malformation of cardiovascular, craniofacial, and skeletal system. Mutations in the SH3PXD2B gene are a common cause in the development of FTHS. We recruited a family with two affected individuals (3-year-old female and 2-month-old male infant) having bilateral clubfoot. Family pedigree shows an autosomal recessive mode of inheritance. DNA was extracted from the blood samples of six members of the family. Whole exome sequencing was done for the two affected individuals and the variant was validated in the whole family by using Sanger sequencing approach. Whole exome sequencing (WES) data analysis identified a rare homozygous variant (c.280C>G; p.R94G) in the SH3PXD2B gene, and Sanger sequencing showed that the same variant perfectly segregates with the phenotype in the pedigree. Moreover, the variant is predicted to be damaging and deleterious by several computation tools. Revisiting the family members for detailed clinical analysis, we diagnosed the patients as having the typical phenotype of FTHS. This study enabled us to correctly diagnose the cases of FTHS in a family initially recruited for having bilateral clubfoot by using WES. Moreover, this study identified a novel homozygous missense variant (c.280C>G; p.R94G) in (NM_001308175.2) the SH3PXD2B gene as a causative variant for autosomal recessive FTHS. This finding supports the evidence that homozygous mutations in the SH3PXD2B gene are the main cause in the development of FTHS.

Morphological Changes Induced by TKS4 Deficiency Can Be Reversed by EZH2 Inhibition in Colorectal Carcinoma Cells.

BACKGROUND: The scaffold protein tyrosine kinase substrate 4 (TKS4) undergoes tyrosine phosphorylation by the epidermal growth factor receptor (EGFR) pathway via Src kinase. The TKS4 deficiency in humans is responsible for the manifestation of a genetic disorder known as Frank-Ter Haar syndrome (FTHS). Based on our earlier investigation, the absence of TKS4 triggers migration, invasion, and epithelial-mesenchymal transition (EMT)-like phenomena while concurrently suppressing cell proliferation in HCT116 colorectal carcinoma cells. This indicates that TKS4 may play a unique role in the progression of cancer. In this study, we demonstrated that the enhancer of zeste homolog 2 (EZH2) and the histone methyltransferase of polycomb repressive complex 2 (PRC2) are involved in the migration, invasion, and EMT-like changes in TKS4-deficient cells (KO). EZH2 is responsible for the maintenance of the trimethylated lysine 27 on histone H3 (H3K27me3). METHODS: We performed transcriptome sequencing, chromatin immunoprecipitation, protein and RNA quantitative studies, cell mobility, invasion, and proliferation studies combined with/without the EZH2 activity inhibitor 3-deazanoplanocine (DZNep). RESULTS: We detected an elevation of global H3K27me3 levels in the TKS4 KO cells, which could be reduced with treatment with DZNep, an EZH2 inhibitor. Inhibition of EZH2 activity reversed the phenotypic effects of the knockout of TKS4, reducing the migration speed and wound healing capacity of the cells as well as decreasing the invasion capacity, while the decrease in cell proliferation became stronger. In addition, inhibition of EZH2 activity also reversed most epithelial and mesenchymal markers. We investigated the wider impact of TKS4 deletion on the gene expression profile of colorectal cancer cells using transcriptome sequencing of wild-type and TKS4 knockout cells, particularly before and after treatment with DZNep. Additionally, we observed changes in the expression of several protein-coding genes and long non-coding RNAs that showed a recovery in expression levels following EZH2 inhibition. CONCLUSIONS: Our results indicate that the removal of TKS4 causes a notable disruption in the gene expression pattern, leading to the disruption of several signal transduction pathways. Inhibiting the activity of EZH2 can restore most of these transcriptomics and phenotypic effects in colorectal carcinoma cells.

Retinal detachment in a child with Frank-ter Haar syndrome.

BACKGROUND: To present a rare case of ocular involvement in a child with Frank-ter Haar syndrome (FTHS) presenting retinal detachment. MATERIALS AND METHODS: Detailed ophthalmological evaluation including examination under general anesthesia, ocular ultrasound, and visual evoked potential testing was completed. Photographic documentation of the physical findings was obtained. RESULTS: A 3-year-old female patient with FTHS was referred to evaluate for possible ophthalmic involvement. The patient presented with the classical dysmorphic abnormalities of the syndrome. Ophthalmologic evaluation revealed a high, against-the-rule corneal astigmatism in the right eye. In the left eye, the red reflex was absent with a suspicious membrane behind the lens, and a sensory exotropia was present. Ultrasonography confirmed retinal detachment with no history of previous trauma. Due to poor visual evoked potentials, no surgery was planned. Astigmatic refractive error was corrected with routine follow-up. CONCLUSIONS: FTHS is associated with multiple ocular involvement such as megalocornea, congenital glaucoma, or colobomas. This case report is the first to describe a high, against-the-rule astigmatism and retinal detachment in a female child with FTHS and demonstrates that an early and detailed ophthalmological examination is essential for these patients.

The Role of the Disrupted Podosome Adaptor Protein (SH3PXD2B) in Frank-Ter Haar Syndrome.

Frank-Ter Haar syndrome (FTHS), sometimes referred to as Ter Haar syndrome, is a rare hereditary disorder that manifests in skeletal, cardiac, and ocular anomalies, including hypertelorism, glaucoma, prominent eyes, and facial abnormalities. In this study, we performed whole-exome sequencing (WES) to identify the genetic component responsible for the phenotype of the index patient, a male infant born to a consanguineous family from Saudi Arabia. The analysis revealed a homozygous missense variant, c.280C>G, in the SH3PXD2B gene, which cosegregates with the familial phenotype with a plausible autosomal-recessive mode of inheritance, indicating a potential disease-causing association. The SH3PXD2B gene encodes a TKS4 podosome adaptor protein that regulates the epidermal growth factor signaling pathway. This study validates the critical function of the TKS4 podosome protein by suggesting a common mechanism underlying the pathogenesis of FTHS.

Anesthetic management of scoliosis operation in a pediatric patient with Frank-ter Haar syndrome: a case report.

Frank-ter Haar syndrome is a rare disorder characterized by multiple skeletal, cardiovascular abnormalities, and facial features. Some of these characteristic facial features are important for anesthesiologists to predict the difficult airway. We present the anesthesia management of an 8-year-old boy with Frank-ter Haar syndrome who underwent posterior spinal instrumentation operation for scoliosis. In these patients, it is vital to anticipate possible difficult intubation before surgery and make all necessary preparations.

Multicentric Osteolysis, Nodulosis, and Arthropathy in two unrelated children with matrix metalloproteinase 2 variants: Genetic-skeletal correlations.

Multicentric Osteolysis, Nodulosis, and Arthropathy (MONA) syndrome is a rare genetic skeletal dysplasia. Its diagnosis can be deceptively similar to childhood-onset genetic skeletal dysplasias and juvenile idiopathic arthritis. We aimed to report the syndrome's clinical and radiologic features with emphasis on skeletal manifestations. And establish relevant phenotype-genotype correlations. We evaluated two boys, 4-and-7-years-old with MONA syndrome. Both patients had consanguineous parents. We verified the diagnosis by correlating the outcomes of clinical, radiologic and molecular analysis. We specifically evaluated the craniofacial morphology and clinical and radiographic skeletal abnormalities. We contextualized the resultant phenotype-genotype correlations to publications on MONA and its differential diagnosis. Skeletal manifestations were the presenting symptoms and mostly restricted to hands and feet in terms of fixed extension deformity of the metacarpophalangeal and flexion deformity of the interphalangeal joints with extension deformity of big toes. There were arthritic symptoms in the older patient especially of the wrists and minute pathologic fractures. The skeletal radiographs showed osteopenia/dysplastic changes of hands and feet. Both patients had variants in the matrix metalloproteinase2 gene which conformed to phenotype of previously reported literature in one patient while the other had a novel variant which conformed to MONA phenotype. Craniofacial abnormalities were present. However, minimal extra-skeletal manifestations. Overall, there is an emerging distinctive skeletal pattern of involvement in terms of both clinical and radiographic features. This includes age of onset and location of presenting skeletal manifestations, chronological order of joint affection, longitudinal disease progression, specifics of skeletal radiographic pathology and craniofacial features. Nevertheless, physicians are cautioned against differential diagnosis of similar genetic skeletal dysplasias and juvenile idiopathic arthritis.

A severe case of Frank-ter Haar syndrome and literature review: Further delineation of the phenotypical spectrum.

Frank-ter Haar syndrome (FTHS) is a rare autosomal recessive syndrome resulting from mutations in the SH3PXD2B gene involved in the formation of podosomes and invadopodia which have a role in extracellular matrix remodelling and cell migration. FTHS is characterized by facial dysmorphism, megalocornea, inconstant glaucoma, variable developmental delay, skeletal and cardiac anomalies. To date, 40 patients have been reported in the literature with a clinical diagnosis of FTHS, only 20 patients having identified mutations. We present a review of these 20 reported patients and describe a patient born to non-consanguineous parents, with intrauterine growth retardation, hypotonia, congenital glaucoma, caudal appendix, scoliosis, camptodactyly, ventricular septal defect, thin corpus callosum and craniofacial features suggestive of FTHS. Clinical evolution resulted in buphthalmos worsening, coarsening of the facial features and respiratory failure leading to death at 4,5 months. Diagnosis was confirmed by the identification of a previously known homozygous mutation c.969delG, p.(Arg324Glyfs*19) in SH3PXD2B. This is the first description of very severe phenotype with lethal respiratory impairment in FTHS. Since very few patients are described in the literature, and 2 out of the 3 patients carrying the c.969delG mutation had a favourable clinical course, more cases are needed to better characterize the phenotype and understand the natural history of this syndrome. Furthermore, we hypothesize that the alteration of podosomes function could lead to a reduction of the extracellular matrix degradation and accumulation of the latter in the extracellular space, which might explain the coarsening of the facial features and the severe refractory glaucoma.

Identification of two novel SH3PXD2B gene mutations in Frank-Ter Haar syndrome by exome sequencing: Case report and review of the literature.

BACKGROUND: Frank-Ter Haar syndrome (FTHS) is an autosomal-recessive disorder characterized by skeletal, cardio-vascular, and eye abnormalities, such as increased intraocular pressure, prominent eyes, and hypertelorism. The most common underlying genetic defect in Frank-Ter Haar syndrome appears to be due to mutations in the SH3PXD2B gene on chromosome 5q35.1. Until now, only six mutations in SH3PXD2B gene have been identified. A genetic heterogeneity of FTHS was suggested in previous studies. DESIGN: FTHS was suspected clinically in a girl of 2years old, born from non-consanguineous Moroccan healthy parents. The patient had been referred to a medical genetics outpatient clinic for dysmorphic facial features. Whole Exome Sequencing (WES) was performed in the patient and her parents, in addition to Sanger sequencing that was carried out to confirm the results. RESULTS: We report the first description of a Moroccan FTHS patient with two novel compound heterozygous mutations c.806G>A; p.Trp269* (maternal allele) and c.892delC; p.Asp299Thrfs*44 (paternal allele) in the SH3PXD2B gene. Sanger sequencing confirmed this mutation in the affected girl and demonstrated that her parents carry this mutation in heterozygous state. CONCLUSION: Our results confirm the clinical diagnosis of FTHS in this reported family and contribute to expand the mutational spectrum of this rare disease. Our study shows also, that exome sequencing is a powerful and a cost-effective tool for the diagnosis of a supposed genetically heterogeneous disorder such FTHS.

Frank-ter Haar syndrome--additional findings?

Frank-ter Haar syndrome is a genetic disease that is transmitted by autosomal recessive pattern with characteristic features such as megalocornea or glaucoma, a prominent coccyx, heart defects, developmental delays, brachycephaly, a wide anterior fontanel, finger flexion deformities, full cheeks and micrognathia. Dentomaxillofacial features of this syndrome are not well documented in the literature. We present of a 21-year-old male with Frank-ter Haar syndrome and some features that may be linked with this syndrome not reported before in the literature.