Syndromic Forms Of Craniosynostosis Research Articles

The role of pathogenic TCF12 variants in children with coronal craniosynostosis-a systematic review with addition of two novel cases.

Craniosynostosis constitutes one of the most common congenital cranial malformations, affecting approximately 6/10,0000 live births. A genetic etiology has long been known for several forms of syndromic craniosynostosis, including pathogenic variants in TWIST1 and FGFR3 in children with Saethre-Chotzen and Muenke syndrome. Over the last decade, reports of genetic aberrations in TCF12 in children with craniosynostosis have emerged, in particular in cases with premature closure of the coronal suture(s). In this study, we, therefore, systematically reviewed the rapidly growing knowledge of TCF12-related coronal craniosynostosis, clearly illustrating its high degree of genotype and phenotype variability. With the two novel cases presented, at least 113 cases of TCF12-related coronal craniosynostosis have currently been reported. By pooling data from several prospectively collected undifferentiated craniosynostosis cohorts (ntotal = 770), we estimate a prevalence of pathogenic TCF12 variants of at least 2%. Overall, pathogenic germline variants in TCF12 are relatively frequent in children with coronal craniosynostosis, accounting for ∼10-20% of TWIST1- and FGFR1/2/3-negative cases, with even higher rates for bicoronal and syndromic cases. Genetic counseling is recommended for all children with craniosynostosis, and involvement of the coronal suture(s) should precipitate TCF12 testing.

Syndromic Craniosynostosis: Cranial Vault Expansion in Infancy.

Syndromic craniosynostosis (CS) represents a relatively uncommon disease process that poses significant reconstructive challenges for the craniofacial surgeon. Although there is considerable overlap in clinical features associated with various forms of syndromic CS, key extracranial features and close examination of the extremities help to distinguish the subtypes. While Virchow's law can easily guide the diagnosis of single suture, nonsyndromic CS, syndromic CS traditionally results in atypical presentations inherent to multiple suture fusion. Coronal ring involvement in isolation or associated with additional suture fusion is the most common pattern in syndromic CS often resulting in turribrachycephaly.

Mechanical loading of cranial joints minimizes the craniofacial phenotype in Crouzon syndrome

Children with syndromic forms of craniosynostosis undergo a plethora of surgical interventions to resolve the clinical features caused by the premature fusion of cranial sutures. While surgical correction is reliable, the need for repeated rounds of invasive treatment puts a heavy burden on the child and their family. This study explores a non-surgical alternative using mechanical loading of the cranial joints to prevent or delay craniofacial phenotypes associated with Crouzon syndrome. We treated Crouzon syndrome mice before the onset of craniosynostosis by cyclical mechanical loading of cranial joints using a custom designed set-up. Cranial loading applied to the frontal bone partially restores normal skull morphology, significantly reducing the typical brachycephalic appearance. This is underpinned by the delayed closure of the coronal suture and of the intersphenoidal synchondrosis. This study provides a novel treatment alternative for syndromic craniosynostosis which has the potential to be an important step towards replacing, reducing or refining the surgical treatment of all craniosynostosis patients.

The outcome of targeted NGS screening in patients with syndromic forms of sagittal and pansynostosis - IL11RA is an emerging core-gene for pansynostosis

Here, we have studied the prevalence and spectrum of genetic alterations in syndromic forms of sagittal and pansynostosis. Eighteen patients with sagittal synostosis (isolated or combined with other synostoses, except coronal) or pansynostosis were phenotypically assessed by retrospective analysis of medical records, three-dimensional computed tomography skull reconstructions, and registered photos. Patient DNAs were analyzed using a targeted next-generation sequencing (NGS) panel including 63 craniosynostosis (CS) related genes. Pathogenic and likely pathogenic variants were found in 72% of the cases, mainly affecting FGFR2, TWIST1, IL11RA, and SKI. Two patients that were negative at NGS screening – one with a supernumerary marker chromosome with duplication of 15q25.2q26.3 and one with a pathogenic PHEX variant – were identified using microarray and single gene analysis, respectively. The overall diagnostic rate in the cohort was thus 83%. We identified two novel likely pathogenic variants in FGFR2 (NM_022970.3: c.811_812delGGinsCC, p.Gly271Pro) and TWIST1 (NM_000474.3: c.476T > A, p.Leu159His), and a novel variant of unclear phenotypic significance in RUNX2 (NM_001024630.3: c.340G > A, p.Val114Ile) which could suggest a modulatory effect. Notably, we also identified three new patients with pansynostosis and a Crouzon-like phenotype with IL11RA mutation. Targeted NGS using a broad panel of CS-related genes is a simple and powerful tool for detecting pathogenic mutations in patients with syndromic forms of CS and multiple suture involvement, in particular pansynostosis. Our results provide additional evidence of an association between pansynostosis and IL11RA, an emerging core gene for autosomal recessive CS.

NGS targeted screening of 100 Scandinavian patients with coronal synostosis

Craniosynostosis (CS), the premature closure of one or more cranial sutures, occurs both as part of a syndrome or in isolation (nonsyndromic form). Here, we have studied the prevalence and spectrum of genetic alterations associated with coronal suture closure in 100 Scandinavian patients treated at a single craniofacial unit. All patients were phenotypically assessed and analyzed with a custom-designed 63 gene NGS-panel. Most cases (78%) were syndromic forms of CS. Pathogenic and likely pathogenic variants explaining the phenotype were found in 80% of the families with syndromic CS and in 14% of those with nonsyndromic CS. Sixty-five percent of the families had mutations in the CS core genes FGFR2, TWIST1, FGFR3, TCF12, EFNB1, FGFR1, and POR. Five novel pathogenic/likely pathogenic variants in TWIST1, TCF12, and EFNB1 were identified. We also found novel variants in SPECC1L, IGF1R, and CYP26B1 with a possible modulator phenotypic effect. Our findings demonstrate that NGS targeted sequencing is a powerful tool to detect pathogenic mutations in patients with coronal CS and further emphasize the importance of thorough assessment of the patient's phenotype for reliable interpretation of the molecular findings. This is particularly important in patients with complex phenotypes and rare forms of CS.

Calvarial osteoblast gene expression in patients with craniosynostosis leads to novel polygenic mouse model.

Craniosynostosis is the premature fusion of the sutures of the calvaria and is principally designated as being either syndromic (demonstrating characteristic extracranial malformations) or non-syndromic. While many forms of syndromic craniosynostosis are known to be caused by specific mutations, the genetic etiology of non-syndromic, single-suture craniosynostosis (SSC) is poorly understood. Based on the low recurrence rate (4–7%) and the fact that recurrent mutations have not been identified for most cases of SSC, we propose that some cases of isolated, single suture craniosynostosis may be polygenic. Previous work in our lab identified a disproportionately high number of rare and novel gain-of-function IGF1R variants in patients with SSC as compared to controls. Building upon this result, we used expression array data from calvarial osteoblasts isolated from infants with and without SSC to ascertain correlations between high IGF1 expression and expression of other osteogenic genes of interest. We identified a positive correlation between increased expression of IGF1 and RUNX2, a gene known to cause SSC with increased gene dosage. Subsequent phosphorylation assays revealed that osteoblast cell lines from cases with high IGF1 expression demonstrated inhibition of GSK3β, a serine/threonine kinase known to inhibit RUNX2, thus activating osteogenesis through the IRS1-mediated Akt pathway. With these findings, we have utilized established mouse strains to examine a novel model of polygenic inheritance (a phenotype influenced by more than one gene) of SSC. Compound heterozygous mice with selective disinhibition of RUNX2 and either overexpression of IGF1 or loss of function of GSK3β demonstrated an increase in the frequency and severity of synostosis as compared to mice with the RUNX2 disinhibition alone. These polygenic mouse models reinforce, in-vivo, that the combination of activation of the IGF1 pathway and disinhibition of the RUNX2 pathway leads to an increased risk of developing craniosynostosis and serves as a model of human SSC.

Research Article A targeted NGS approach to identify a c.352C>G variant in the TWIST1 gene in an Albanian family with Saethre–Chotzen syndrome

A targeted next generation sequencing (NGS) approach analysing contemporaneously 20 different genes mainly involved in craniosynostosis was adopted to molecularly diagnose the family of a 2-years old girl affected by Saethre–Chotzen syndrome, a syndromic form of craniosynostosis. The identified pathogenic variant in the TWIST1 gene lies in a conserved residue (Arg118) that shifts from a positively charged amino acid to a non-polar amino acid and segregates in all the examined affected familial members, although with variable phenotypic expression. An accurate molecular diagnosis is of obvious value for the clinical management of individuals with isolated or syndromic craniosynostosis to define their medical needs, the recurrence risk and allow the identification of available therapeutic opportunity. Given the high number of associated genes, an NGS approach is the election choice to increase the yield of genetic diagnosis, leading to an expansion of the genotypic and phenotypic spectrum of these rare syndromes

FGFR-associated craniosynostosis syndromes and gastrointestinal defects.

Craniosynostosis is a relatively common birth defect characterized by the premature fusion of one or more cranial sutures. Examples of craniosynostosis syndromes include Crouzon (CS), Pfeiffer (PS), and Apert (AS) syndrome, with clinical characteristics such as midface hypoplasia, hypertelorism, and in some cases, limb defects. Mutations in Fibroblast Growth Factor Receptor-2 comprise the majority of known mutations in syndromic forms of craniosynostosis. A number of clinical reports of FGFR-associated craniosynostosis patients and mouse mutants have been linked to gastrointestinal tract (GIT) disorders, leading to the hypothesis of a direct link between FGFR-associated craniosynostosis syndromes and GIT malformations. We conducted an investigation to determine GIT symptoms in a sample of FGFR-associated craniosynostosis syndrome patients and a mouse model of CS containing a mutation (W290R) in Fgfr2. We found that, compared to the general population, the incidence of intestinal/bowel malrotation (IM) was present at a higher level in our sample population of patients with FGFR-associated craniosynostosis syndromes. We also showed that the mouse model of CS had an increased incidence of cecal displacement, suggestive of IM. These findings suggest a direct relationship between FGFR-related craniosynostosis syndromes and GIT malformations. Our study may shed further light on the potential widespread impact FGFR mutations on different developmental systems. Based on reports of GIT malformations in children with craniosynostosis syndromes and substantiation with our animal model, GIT malformations should be considered in any child with an FGFR2-associated craniosynostosis syndrome. © 2016 Wiley Periodicals, Inc.

Aberrant facial flushing following monobloc fronto-facial distraction.

Patients with syndromic forms of craniosynostosis may experience functional problems such as raised intracranial pressure, proptosis, obstructive sleep apnoea and failure to thrive. The monobloc fronto-facial advancement with osteogenic distraction is increasingly used to correct these functional problems in one procedure as well as improve appearance. The authors report the phenomenon of post operative aberrant facial flushing - an unusual and previously unreported complication of the procedure. The case notes of 80 consecutive patients undergoing fronto-facial advancement by distraction using the rigid external distraction device (RED) were reviewed for features of aberrant facial flushing. Four out of eighty individuals developed facial flushing after monobloc fronto-facial distraction using the rigid external distractor (RED) frame. All were female with Crouzon or Pfeiffer syndromes causing the severe functional problems for which they underwent the surgery. They were aged 6-8 years. Following removal of the frame, they developed intermittent but severe facial flushing. The flushing spontaneously settled in three patients after up to four years but persists in the other child seven years after her surgery. Aberrant facial flushing is a rare but significant complication of monobloc fronto-facial surgery. It occurred in 4 of our 80 (5%) patients. The skull base osteotomies essential for the procedure are made anterior to the pterygopalatine ganglion and it is our contention that damage from these was responsible for a neuropraxia of its efferent nerve branches. A review of the autonomic control of the facial vascular system suggests that the phenomenon is due to an unequal process of recovery that leaves the cutaneous vasodilating parasympathetic or beta-adrenergic innervation relatively unopposed - a situation that persists until with time a normal balance of autonomic input is achieved.

Endoscopic temporalis muscle flap in maxillo-facial surgery

gesting genetic heterogeneity. We therefore aimed to elucidate the underlying molecular basis of syndromic craniosynostosis in mutation negative patients. Methods:We performed whole exome sequencing in a patient clinically diagnosed with Crouzon syndrome in whom mutations in known craniosynostosis genes have been previously excluded. Since consanguinitywas suspected, variants in regions of homozygosity were prioritized. Shortlisted, causative mutations were re-sequenced and further checked for annotation in over 6000 exomes of the Exome Variant Server (EVS). Direct sequencing of all coding regions of the newly identified candidate gene was then conducted in 12 additional syndromic cases. Results: We detected a total of three different mutations in the low-density lipoprotein-related protein 2, encoded by LRP2, a gene known to be implicated in Donnai-Barrow syndrome but which has not been associated with the development of craniosynostosis so far. One homozygous splice-site mutation (c.8452 + 1 G/T) in a patient with Crouzon syndrome was located in the LRP domain class A. Another two cases with unclassified syndromic forms of craniosynostosis, carried a homozygous and heterozygous missense substitution (p.R3236Q and p.4019K) within the LRP domain class B and the calcium-binding EGF-like domain respectively. Conclusions: In this study, we were able to identify LRP2 as a novel gene underlying syndromic forms of craniosynostosis. Additional functional studies on LRP2 and its downstream molecules will further enhance our understanding on the regulation of cranial suture morphogenesis and fusion.

Intrauterine Fetal Constraint Induces Chondrocyte Apoptosis and Premature Ossification of the Cranial Base

The spheno-occipital synchondrosis is an important growth center of the craniofacial skeleton and a primary site of malformation in syndromic forms of craniosynostosis. Clinical and laboratory investigations have demonstrated that premature closure of cranial vault sutures in nonsyndromic craniosynostosis is associated with characteristic alterations in cranial base morphology. However, a causal link between premature fusion of calvarial sutures and changes in the cranial base remains elusive. The purpose of these experiments was to test the hypothesis that intrauterine head constraint produces ultrastructural changes in the spheno-occipital synchondroses of fetal mice. Fetal constraint was induced through uterine cerclage of six pregnant C57Bl/6 mice on the eighteenth day of gestation. Fetuses were harvested after growing to 24, 48, and 72 hours beyond the normal 20-day gestational period. Between six and nine fetuses were harvested at all time points in both treatment and control groups. The morphology and cell biology of the spheno-occipital synchondroses, in constrained fetuses and unconstrained controls, were examined using hematoxylin and eosin-stained sections. Chondrocyte apoptosis was examined using terminal deoxynucleotidyl transferase-mediated dUDP end-labeling assays and electron microscopy. In nonconstrained animals, the spheno-occipital synchondrosis demonstrated normal architecture and normal chondrocyte morphology at all time points. In contrast, intrauterine constraint resulted in a progressive disruption of the normal cellular architecture of the spheno-occipital synchondrosis over 72 hours, with premature ossification of the synchondrosis. Widespread chondrocyte apoptosis within the synchondrosial growth center was demonstrated by terminal deoxynucleotidyl transferase-mediated dUDP end-labeling assays and electron microscopy. These experiments confirm the ability of intrauterine constraint to induce changes in the morphology and cell biology of the cranial base in synostotic fetuses.

Temporal-spatial expression of E-cadherin and FGF-2 in neural crest derived fusing cranial sutures

Abstract Introduction: Understanding cranial suture developmental biology is important in elucidating the pathogenesis of craniosynostosis. Although recent studies in cranial suture biology have focused on growth factors and transcription factors, few have investigated adhesion molecules and the role they may play in cell migration and bone formation. Methods: RNA were extracted from posterior frontal (PF) fusing suture complexes from mice at serial time-points (p1, p3, p5, p7, p9, p11, p13, p15, p25 and p35) and were used to generate cDNA for microarray and quantitative real-time (qRT) PCR analysis. We performed a focused analysis of cell adhesion molecules. In addition, time-matched calvaria were analyzed for morphometric analysis, H&E staining, and immunohistochemistry. Results: Our microarray data revealed an over 4 fold increase in expression of E-cadherin, a cell-cell adhesion molecule and an osteoblast differentiation marker, in the PF sutures, compared to that of SAG suture during fusion. This differential expression was confirmed by qRT PCR. Expression of E-cahderin was preceded by an increased expression of FGF-2 two days earlier. FGF-2 stimulation is known to promote skeletogenic differentiaion of premigratory neural crest cells (NCC) and increase E-cadherin expression in osteoblasts. Immunohistochemistry reveals an increase expression of E-cadherin in PF suture at the osteogenic fronts during fusion in areas of cell gathering. Conclusions: Here we describe E-cadherin and FGF-2 temporal-spatial expression pattern in the neural crest derived fusing PF suture. This may add insight into the role cadherins may play in syndromic forms of craniosynostosis associated with FGFR gain-of-function mutations.

The BMP antagonist noggin regulates cranial suture fusion.

During skull development, the cranial connective tissue framework undergoes intramembranous ossification to form skull bones (calvaria). As the calvarial bones advance to envelop the brain, fibrous sutures form between the calvarial plates. Expansion of the brain is coupled with calvarial growth through a series of tissue interactions within the cranial suture complex. Craniosynostosis, or premature cranial suture fusion, results in an abnormal skull shape, blindness and mental retardation. Recent studies have demonstrated that gain-of-function mutations in fibroblast growth factor receptors (fgfr) are associated with syndromic forms of craniosynostosis. Noggin, an antagonist of bone morphogenetic proteins (BMPs), is required for embryonic neural tube, somites and skeleton patterning. Here we show that noggin is expressed postnatally in the suture mesenchyme of patent, but not fusing, cranial sutures, and that noggin expression is suppressed by FGF2 and syndromic fgfr signalling. Since noggin misexpression prevents cranial suture fusion in vitro and in vivo, we suggest that syndromic fgfr-mediated craniosynostoses may be the result of inappropriate downregulation of noggin expression.

The Detection and Management of Intracranial Hypertension after Initial Suture Release and Decompression for Craniofacial Dysostosis Syndromes

We performed a retrospective study of 107 consecutive patients with syndromic forms of craniosynostosis (craniofacial dysostosis) seen by the craniofacial team at the Hospital for Sick Children between 1986 and 1992. There were 51 patients with Crouzon's syndrome, 33 with Apert's syndrome, 8 with Pfeiffer syndrome, 11 with Saethre-Chotzen syndrome, and 4 with kleeblättschadel anomaly. Six patients developed raised intracranial pressure (ICP) after initial suture release and decompression (Apert's syndrome, three patients; Pfeiffer syndrome, one patient; Saethre-Chotzen syndrome, two patients). Raised ICP was considered in those children who returned with a bulging fontanelle, progressive frontal bone protrusion, intermittent headaches, irritability, and vomiting. The diagnosis of raised ICP was based on papilledema (four patients), progressive macrocephaly (one patient), and ICP monitoring (one patient). No child in this group had hydrocephalus requiring cerebrospinal fluid diversion. Once raised ICP was detected in these children, a second operation was immediately performed to reduce the ICP with the intention of expanding the volume of the cranial cavity. The second procedures included: anterior cranial vault and upper orbital reshaping (four patients), posterior cranial vault reshaping (one patient), and total cranial vault reshaping (one patient). There were no perioperative complications in these patients, although one patient showed subsequent recurrence of raised ICP requiring further cranial vault re-expansion. At follow-up, ranging from 3 to 7 years, all six patients were asymptomatic without evidence of raised ICP. In our series, raised ICP occurred in 6% of the children with a craniofacial dysostosis syndrome after initial suture release and decompression.(ABSTRACT TRUNCATED AT 250 WORDS)