Mutation screening in patients with syndromic craniosynostoses indicates that a limited number of recurrent FGFR2 mutations accounts for severe forms of Pfeiffer syndrome

Perinatal imaging findings of a fetus with Pfeiffer syndrome and a heterozygous c.1019A>G, p.Tyr340Cys (Y340C) mutation in FGFR2 presenting a cloverleaf skull, craniosynostosis and short limbs on prenatal ultrasound mimicking thanatophoric dysplasia type II

OBJECTIVE

We present perinatal imaging findings of a fetus with Pfeiffer syndrome and a heterozygous c.1019A>G, p.Tyr340Cys (Y340C) mutation in FGFR2 presenting a cloverleaf skull, craniosynostosis and short limbs on prenatal ultrasound mimicking thanatophoric dysplasia type II (TD2).

CASE REPORT

A 37-year-old, gravida 2, para 1, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 46,XY. However, craniofacial anomaly was found on prenatal ultrasound at 21 weeks of gestation, which showed a cloverleaf skull with severe craniosynostosis and relatively short straight long bones. Fetal magnetic resonance imaging (MRI) analysis at 22 weeks of gestation showed a cloverleaf skull, proptosis and relatively shallowing of the sylvian fissures. Prenatal ultrasound at 24 weeks of gestation showed a fetus with a cloverleaf skull with a biparietal diameter (BPD) of 6.16 cm (equivalent to 24 weeks), an abdominal circumference (AC) of 18.89 cm (equivalent to 24 weeks) and a femur length (FL) of 3.65 cm (equivalent to 21 weeks). A tentative diagnosis of TD2 was made. The pregnancy was subsequently terminated, and a 928-g malformed fetus was delivered with severe craniosynostosis, proptosis, midface retrusion, a cloverleaf skull, broad thumbs and broad big toes. The broad thumbs were medially deviated. Whole body X-ray showed a cloverleaf skull and straight long bones. However, molecular analysis of FGFR3 on the fetus revealed no mutation in the target regions. Subsequent whole exome sequencing (WES) on the DNA extracted from umbilical cord revealed a heterozygous c.1019A>G, p.Tyr340Cys (Y340C) mutation in the FGFR2 gene.

CONCLUSION

Fetuses with a Y340C mutation in FGFR2 may present a cloverleaf skull on prenatal ultrasound, and WES is useful for a rapid differential diagnosis of Pfeiffer syndrome from TD2 under such a circumstance.

The genetic basis of hydrocephalus: genes, pathways, mechanisms, and global impact

Hydrocephalus (HC) is a heterogenous disease characterized by alterations in cerebrospinal fluid (CSF) dynamics that may cause increased intracranial pressure. HC is a component of a wide array of genetic syndromes as well as a secondary consequence of brain injury (intraventricular hemorrhage (IVH), infection, etc.) that can present across the age spectrum, highlighting the phenotypic heterogeneity of the disease. Surgical treatments include ventricular shunting and endoscopic third ventriculostomy with or without choroid plexus cauterization, both of which are prone to failure, and no effective pharmacologic treatments for HC have been developed. Thus, there is an urgent need to understand the genetic architecture and molecular pathogenesis of HC. Without this knowledge, the development of preventive, diagnostic, and therapeutic measures is impeded. However, the genetics of HC is extraordinarily complex, based on studies of varying size, scope, and rigor. This review serves to provide a comprehensive overview of genes, pathways, mechanisms, and global impact of genetics contributing to all etiologies of HC in humans.

Syndromic Craniofacial Disorders

This article reviews the most common craniofacial syndromes encountered in clinical practice. Key physical features of each condition are highlighted to aid in accurate recognition and diagnosis. Optimal individualized treatment approaches are discussed.

Candidate genes for obstructive sleep apnea in non-syndromic children with craniofacial dysmorphisms - a narrative review

Pediatric obstructive sleep apnea (POSA) is a complex disease with multifactorial etiopathogenesis. The presence of craniofacial dysmorphisms influencing the patency of the upper airway is considered a risk factor for POSA development. The craniofacial features associated with sleep-related breathing disorders (SRBD) - craniosynostosis, retrognathia and micrognathia, midface and maxillary hypoplasia - have high heritability and, in a less severe form, could be also found in non-syndromic children suffering from POSA. As genetic factors play a role in both POSA and craniofacial dysmorphisms, we hypothesize that some genes associated with specific craniofacial features that are involved in the development of the orofacial area may be also considered candidate genes for POSA. The genetic background of POSA in children is less explored than in adults; so far, only one genome-wide association study for POSA has been conducted; however, children with craniofacial disorders were excluded from that study. In this narrative review, we discuss syndromes that are commonly associated with severe craniofacial dysmorphisms and a high prevalence of sleep-related breathing disorders (SRBD), including POSA. We also summarized information about their genetic background and based on this, proposed 30 candidate genes for POSA affecting craniofacial development that may play a role in children with syndromes, and identified seven of these genes that were previously associated with craniofacial features risky for POSA development in non-syndromic children. The evidence-based approach supports the proposition that variants of these candidate genes could lead to POSA phenotype even in these children, and, thus, should be considered in future research in the general pediatric population.

FGF signaling in cranial suture development and related diseases

Suture mesenchymal stem cells (SMSCs) are a heterogeneous stem cell population with the ability to self-renew and differentiate into multiple cell lineages. The cranial suture provides a niche for SMSCs to maintain suture patency, allowing for cranial bone repair and regeneration. In addition, the cranial suture functions as an intramembranous bone growth site during craniofacial bone development. Defects in suture development have been implicated in various congenital diseases, such as sutural agenesis and craniosynostosis. However, it remains largely unknown how intricate signaling pathways orchestrate suture and SMSC function in craniofacial bone development, homeostasis, repair and diseases. Studies in patients with syndromic craniosynostosis identified fibroblast growth factor (FGF) signaling as an important signaling pathway that regulates cranial vault development. A series of in vitro and in vivo studies have since revealed the critical roles of FGF signaling in SMSCs, cranial suture and cranial skeleton development, and the pathogenesis of related diseases. Here, we summarize the characteristics of cranial sutures and SMSCs, and the important functions of the FGF signaling pathway in SMSC and cranial suture development as well as diseases caused by suture dysfunction. We also discuss emerging current and future studies of signaling regulation in SMSCs.

De Novo Heterozygous Mutation in FGFR2 Causing Type II Pfeiffer Syndrome

Pfeiffer syndrome (PS) is an autosomal dominant disorder with three subtypes stemming from heterozygous mutations in the fibroblast growth factors FGFR1 and FGFR2. The subtypes overlap with heterogeneous clinical manifestations and variable prognosis dependent on neurological and respiratory compromise that impact short- and long-term outcomes and survival. We present a male, term infant with type II PS that was diagnostically suspected antenatally based on three-dimensional ultrasonographic findings that were confirmed postnatally by craniofacial tomography and magnetic resonance imaging. A new generation sequencing panel identified a unique de novo FGFR2, c.335 A > G p. Tyr112Cys variant, the first of its kind, and features that closely aligned with subtype II PS. Initial molecular results categorized the mutation as nonpathogenic, but it was later reclassified as pathogenic. Antenatal, multidisciplinary parental counseling about the tentative diagnosis and prognosis facilitated postnatal decisions that culminated in an informed choice for palliative care and early demise.

A dysmorphic mouse model reveals developmental interactions of chondrocranium and dermatocranium

The cranial endo- and dermal skeletons, which comprise the vertebrate skull, evolved independently over 470 million years ago and form separately during embryogenesis. In mammals, much of the cartilaginous chondrocranium is transient, undergoing endochondral ossification or disappearing, so its role in skull morphogenesis is not well studied and it remains an enigmatic structure. We provide complete three-dimensional (3D) reconstructions of the laboratory mouse chondrocranium from embryonic day 13.5 through 17.5 using a novel methodology of uncertainty-guided segmentation of phosphotungstic enhanced 3D microcomputed tomography images with sparse annotation. We evaluate the embryonic mouse chondrocranium and dermatocranium in 3D and delineate the effects of a Fgfr2 variant on embryonic chondrocranial cartilages and on their association with forming dermal bones using the Fgfr2c^C342Y/+ Crouzon syndrome mouse. We show that the dermatocranium develops outside of and in shapes that conform to the chondrocranium. Results reveal direct effects of the Fgfr2 variant on embryonic cartilage, on chondrocranium morphology, and on the association between chondrocranium and dermatocranium development. Histologically we observe a trend of relatively more chondrocytes, larger chondrocytes, and/or more matrix in the Fgfr2c^C342Y/+ embryos at all timepoints before the chondrocranium begins to disintegrate at E16.5. The chondrocrania and forming dermatocrania of Fgfr2c^C342Y/+ embryos are relatively large, but a contrasting trend begins at E16.5 and continues into early postnatal (P0 and P2) timepoints, with the skulls of older Fgfr2c^C342Y/+ mice reduced in most dimensions compared to Fgfr2c^+/+ littermates. Our findings have implications for the study and treatment of human craniofacial disease, for understanding the impact of chondrocranial morphology on skull growth, and potentially on the evolution of skull morphology.

Phenotypic variability of syndromic craniosynostosis caused by c.833G > T in FGFR2: Clinical and genetic evaluation of eight patients from a five-generation family

Objective

Craniosynostosis is the result of the early fusion of cranial sutures. Syndromic craniosynostosis includes but not limited by Crouzon syndrome and Pfeiffer syndrome. Considerable phenotypic overlap exists among these syndromes and mutations in FGFR2 may cause different syndromes. This study aims to investigate the explanation of the phenotypic variability via clinical and genetic evaluation for eight patients in a large pedigree.

Methods

For each patient, comprehensive physical examination, cranial plain CT scan with three‐dimensional CT reconstruction (3D‐CT), and eye examinations were conducted. Whole exome sequencing was applied for genetic diagnosis of the proband. Variants were analyzed and interpreted following the ACMG/AMP guidelines. Sanger sequencing was performed to reveal genotypes of all the family members.

Results

A pathogenic variant in the FGFR2 gene, c.833G > T (p.C278F), was identified and proved to be co‐segregate with the disease. Some symptoms of head, hearing, vision, mouth, teeth expressed differently by affected individuals. Nonetheless, all the eight patients manifested core symptoms of Crouzon syndrome without abnormality in the limbs, which could exclude diagnosis of Pfeiffer syndrome.

Conclusion

We have established clinical and genetic diagnosis of Crouzon syndrome for eight patients in a five‐generation Chinese family. Variability of clinical features among these familial patients was slighter than that in previously reported sporadic cases.

Posterior Vault Distraction Outcomes in Patients with Severe Crouzon Syndrome Resulting from Ser347Cys and Ser354Cys Mutations

BACKGROUND

In this study, the authors present the outcomes of 4 patients with a severe form of Crouzon syndrome characterized by mutation of fibroblast growth factor receptor 2 (FGFR2) c.1040 C > G p.Ser347Cys or the pathogenic c.1061C > G p.Ser354Cys variant of FGFR2, who underwent posterior vault distraction osteogenesis (PVDO) to alleviate elevated intracranial pressure.

METHODS

Patients with diagnosed Crouzon syndrome who were found by genetic testing to have an FGFR2 c.1040 C > G p.Ser347Cys mutation or the c.1061C > G p.Ser354Cys variant were included. Outcome data and presence of hydrocephalus, Chiari Malformation type I (CMIs), and the presence/absence of a tracheostomy were recorded.

RESULTS

Three patients with the FGFR2 c.1040 C > G p.Ser347Cys mutation and 1 with the pathogenic FGFR2 c.1061C > G p.Ser354Cys variant were identified as having characteristics of severe Crouzon syndrome. The mean age at PVDO was 15 months and the mean posterior advancement was 20 mm. All 4 patients experienced sufficient relief of the elevated intracranial pressure from the PVDO to prevent the need for shunt placement, stabilize the ventricular dimensions (n = 2), and resolve the CMIs (n = 2). Intracranial pressure screening ruled out malignant cerebrospinal fluid volume increase.

CONCLUSIONS

PVDO effectively prevented hydrocephalus and resolved CMIs, successfully alleviating intracranial pressure and maximizing clinical outcomes for patients with severe Crouzon syndrome.

Orbital and Periorbital Dysmorphology in Untreated Pfeiffer Syndrome

BACKGROUND

Visual impairment secondary to orbital and periorbital dysmorphology is frequent in Pfeiffer syndrome patients. The etiopathogenesis of this aberrancy, however, remains unclear.

METHODS

Untreated Pfeiffer syndrome patients (n = 31) and normal control subjects (n = 43) were compared. Craniometric and volumetric analyses related to the orbital and periorbital anatomy were performed using Materialise (Leuven, Belgium) software.

RESULTS

Overall, orbital cavity volume of Pfeiffer patients is reduced by 28 percent (p < 0.001), compared to normal, starting before 3 months of age (p = 0.004). Globe volume was diminished by 10 percent (p = 0.041) before 3 months of age, yet tended to catch up thereafter. However, the retrobulbar soft-tissue volume remained smaller beyond 1 year of age (17 percent, p = 0.003). Globe volume projection beyond the bony orbit increased in all observed ages (82 percent, p < 0.001). The volumes of sphenoid bone, maxilla, and mandible proportionately were restricted by 24 to 25 percent (p = 0.003 to 0.035) before 3 months of age. The volume of maxilla and mandible gradually approximate normal; however, the sphenoid bone volume in Pfeiffer patients remains less than normal (p = 0.002) into childhood. The anteroposterior length of both the zygoma and the maxilla was reduced by 14 percent (p < 0.001). Anterior positioning of the zygoma is less by 23 percent (p < 0.001) in Pfeiffer patients overall, with anterior positioning of maxilla reduced similarly by 23 percent (p < 0.001).

CONCLUSIONS

Pfeiffer syndrome patients develop decreased retrobulbar soft-tissue and globe volume, along with a restricted orbital cavity volume in infancy. Significant hypoplasia of the sphenoid bone is associated with more severe central facial (maxilla) retrusion, compared to lateral facial structures (zygoma).

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, II.

Development and validation of an expanded targeted sequencing panel for non-invasive prenatal diagnosis of sporadic skeletal dysplasia

Background

Skeletal dysplasia (SD) is one of the most common inherited neonatal disorders worldwide, where the recurrent pathogenic mutations in the FGFR2, FGFR3, COL1A1, COL1A2 and COL2A1 genes are frequently reported in both non-lethal and lethal SD. The traditional prenatal diagnosis of SD using ultrasonography suffers from lower accuracy and performed at latter gestational stage. Therefore, it remains in desperate need of precise and accurate prenatal diagnosis of SD in early pregnancy. With the advancements of next-generation sequencing (NGS) technology and bioinformatics analysis, it is feasible to develop a NGS-based assay to detect genetic defects in association with SD in the early pregnancy.

Methods

An ampliseq-based targeted sequencing panel was designed to cover 87 recurrent hotspots reported in 11 common dominant SD and run on both Ion Proton and NextSeq550 instruments. Thirty-six cell-free and 23 genomic DNAs were used for assay developed. Spike-in DNA prepared from standard sample harboring known mutation and normal sample were also employed to validate the established SD workflow. Overall performances of coverage, uniformity, and on-target rate, and the detecting limitations on percentage of fetal fraction and read depth were evaluated.

Results

The established targeted-seq workflow enables a single-tube multiplex PCR for library construction and shows high amplification efficiency and robust reproducibility on both Ion Proton and NextSeq550 platforms. The workflow reaches 100% coverage and both uniformity and on-target rate are > 96%, indicating a high quality assay. Using spike-in DNA with different percentage of known FGFR3 mutation (c.1138 G > A), the targeted-seq workflow demonstrated the ability to detect low-frequency variant of 2.5% accurately. Finally, we obtained 100% sensitivity and 100% specificity in detecting target mutations using established SD panel.

Conclusions

An expanded panel for rapid and cost-effective genetic detection of SD has been developed. The established targeted-seq workflow shows high accuracy to detect both germline and low-frequency variants. In addition, the workflow is flexible to be conducted in the majority of the NGS instruments and ready for routine clinical application. Taken together, we believe the established panel provides a promising diagnostic or therapeutic strategy for prenatal genetic testing of SD in routine clinical practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01063-1.

Autopsy Case of Pfeiffer Syndrome Type 2, a Phenotype of Fibroblast Growth Factor Receptor-Associated Craniosynostosis Syndromes, with Tracheal Cartilage Sleeve and Abnormal Hyperplasia of Bronchial Cartilages

BACKGROUND Pfeiffer syndrome (PS) is a fibroblast growth factor receptor (FGFR)-associated craniosynostosis syndrome, characterized by abnormally broad and medially deviated thumbs and great toes. Tracheal cartilage sleeve (TCS) is associated with several FGFR-associated craniosynostosis syndromes, including PS. TCS is an airway malformation in which the tracheal cartilage rings fuse with each other to form a sleeve of cartilage. CASE REPORT The patient was a 4-year-old girl with PS, TCS, and abnormal hyperplasia of non-fused intrapulmonary cartilages. The patient showed cranial dysplasia on prenatal ultrasonography. At birth, a cloverleaf skull in association with hydrocephalus and digital malformations was apparent. These findings were consistent with PS type 2. The diagnosis of PS type 2 was confirmed from a genetic test detecting a FGFR2 mutation (Y340C). During the clinical course, she underwent several surgeries, including ventriculoperitoneal shunts, sequential cranioplasty surgeries, and tracheotomy due to upper airway abnormalities. At 4 years old, she died of multiple organ failure following aspiration pneumonia. The autopsy revealed that the tracheal cartilages had fused with each other, resulting in a condition called TCS, in which the cartilage rings and tracheal ligaments were absent. The lungs were poorly aerated, and the dilated bronchi had thickened walls surrounded by many cartilage fragments, mainly at the hilum. These cartilages tended to overlap at both ends, did not fuse, and were greatly altered in size and shape. CONCLUSIONS We report the results of autopsy for PS with the first histopathological findings for the lungs and other visceral organs.

Craniosynostosis: Clinical Presentation, Genetics, and Prenatal Diagnosis

Importance

Craniosynostosis is a fetal condition caused by premature closure of the cranial sutures. Through provider awareness, we can raise suspicion in high-risk individuals, increase prenatal detection, optimize genetic testing, perform appropriate antenatal surveillance and delivery planning, and allow for a comprehensive, multidisciplinary approach to treatment.

Objective

The aim of this study was to review what is currently known regarding the genetics, pathophysiology, diagnosis, and treatment of craniosynostosis for the obstetric care provider.

Evidence Acquisition

A comprehensive literature review was performed using the PubMed database with the search term "craniosynostosis." The search was limited to the English language.

Results

A total of 220 articles were identified, and a total of 53 were used in completion of this article. The results highlight the multiple factors involved with abnormal suture formation, including various genetic factors. Although rare at this time, prenatal detection can allow families to prepare and practitioners to provide appropriate clinical treatment. Both 3-dimensional sonography and magnetic resonance imaging have been identified as modalities to aid in detection for high-risk individuals. Early referral allows for less-invasive surgical outcomes with lower complication rates.

Results

Familiarity with craniosynostosis among obstetric providers can improve patient counseling, prenatal detection rates, and appropriate antepartum, intrapartum, and postpartum counseling.

Severe craniolacunae and upper and lower extremity anomalies resulting from Crouzon syndrome, FGFR2 mutation, and Ser347Cys variant

Crouzon syndrome is a rare form of syndromic craniosynostosis (SC) characterized by premature fusion of the cranial and facial sutures, elevated intracranial pressure, varying degrees of ocular exposure due to exorbitism, and airway compromise caused by midface retrusion. Craniolacunae and upper and lower extremity anomalies are not frequently found in Crouzon syndrome. We present a girl with Crouzon syndrome caused by c.1040 C > G, p.Ser347Cys, a pathogenic mutation in the FGFR2 gene with atypical characteristics, including craniolacunae resembling severe Swiss cheese type of bone formation, and upper and lower extremity anomalies which are more commonly associated with Pfeiffer syndrome patients. Distinguishing between severe Crouzon syndrome patients and patients who have mild and/or moderate Pfeiffer syndrome can be challenging even for an experienced craniofacial surgeon. An accurate genotype diagnosis is essential to distinguishing between these syndromes, as it provides predictors for neurosurgical complications and facilitates appropriate family counseling related to long-term outcomes.

Changes in FGFR2 amino-acid residue Asn549 lead to Crouzon and Pfeiffer syndrome with hydrocephalus

Mutations in Fibroblast Growth Factor Receptor II (FGFR2) have been identified in patients with Crouzon and Pfeiffer syndrome, among which rare mutations of the intracellular tyrosine kinase domain. Correlating subtle phenotypes with each rare mutation is still in progress. In Necker-Enfants Malades Hospital, we identified three patients harboring three different pathogenic variants of the same amino acid residue Asn-549 located in this domain: in addition to a very typical crouzonoid appearance, they all developed clinically relevant hydrocephalus, which is an inconstant feature of Crouzon and Pfeiffer syndrome. Overall, FGFR2 tyrosine kinase domain mutations account for 5/67 (7.4%) cases in our hospital. We describe a novel mutation, p.Asn549Ser, and new cases of p.Asn549His and p.Asn549Thr mutations, each reported once before. Our three cases of Asn-549 mutations, alongside with rare previously reported cases, show that these patients are at higher risk of hydrocephalus. Clinical and imaging follow-up, with possible early surgery, may help prevent secondary intellectual disability.

Novel mutation detection in craniosynostosis promotes characterization, identification, gene expression, tissue engineering and helps clinical practice and translational research

Introduction

Craniosynostosis (CS) syndrome is an autosomal dominant condition (ADC) classically combining with CS and nonsyndromic CS (NSCS) including digital anomalies of the hands and feet. The majority of cases caused by a heterozygous mutation (HM) in the third immunoglobulin-like domain (IgIII) of fibroblast growth factor receptor (FGFR) 2 mutations outside this region of the protein.

Material and Methods

We tried to find out the spectrum of genes involved in CS syndrome caused by the heterozygous missense mutation, the IgII and IgIII of FGFR2. FGFR3, FGFR4, TWIST, and MSX genes were performed and verified through the Indian population with CS children.

Results

We find out that at conserved linker region (LR), the changes occurred among the larger families. Independent genetic origins, but phenotypic similarities add to the evidence supporting the theory of selfish spermatogonial selective advantage for this rare gain-of-function FGFR2 mutation. Polygenic novel mutation in both syndromic and nonsyndromic cases of CS promotes the translational research and holds a great promise to reproduce the molecular-based therapy and treatment as well. In this article, we summarized that genes involved in CS as evidence-based approach for characterization, identification, gene expression, and tissue engineering. We also described other related genes and proteins for the CS involvement and improvement of the diseases progression.

Conclusion

HM again repeated the old story for both groups of syndromic CS and NSCS of Asian Indian children. Here, for the first time, we clearly reported that IgIII of FGFR2 mutations outside this region of the protein and tyrosine kinase (TK1 and TK2) responsible for both in molecular and cellular level for CS. It adds an evidence for future molecular targeting therapy to repair CS.

Clinical study and some molecular features of Mexican patients with syndromic craniosynostosis

BACKGROUND

Craniosynostosis is one of the major genetic disorders affecting 1 in 2,100-2,500 live newborn children. Environmental and genetic factors are involved in the manifestation of this disease. The suggested genetic causes of craniosynostosis are pathogenic variants in FGFR1, FGFR2, FGFR3, and TWIST1 genes.

METHODS

In order to describe their major clinical characteristics and the presence of pathogenic variants, a sample of 36 Mexican patients with craniosynostosis diagnosed as: Crouzon (OMIM 123,500), Pfeiffer (OMIM 101,600), Apert (OMIM 101,200), Saethre-Chotzen (OMIM 101,400), and Muenke (OMIM 602,849) was analyzed.

RESULTS

In addition to craniosynostosis, most of the patients presented hypertelorism, midface hypoplasia, and abnormalities in hands and feet. To detect the pathogenic variants p.Pro252Arg FGFR1 (OMIM 136,350), p.Ser252Trp, p.Pro253Arg FGFR2 (OMIM 176,943), p.Pro250Arg, FGFR3 (OMIM 134,934), and p.Gln119Pro TWIST1 (OMIM 601,622), PCR amplification and restriction enzyme digestion were performed. Four and two patients with Apert presented the pathogenic variants p.Ser252Trp and p.Pro253Arg in FGFR2, respectively (with a frequency of 11.1% and 5.5%). The p.Pro250Arg pathogenic variant of FGFR3 was found in a patient with Muenke (with a frequency of 2.8%). The above percentages were calculated with the total number of patients.

CONCLUSION

The contribution of this work is discreet, since only 4 genes were analyzed and sample size is small. However, this strategy could be improved by sequencing the FGFR1, FGFR2, FGFR3, and TWIST1 genes, to determine different pathogenic variants. On the other hand, it would be important to include other genes, such as TCF12 (OMIM 600,480), MSX2 (OMIM 123,101), RAB23 (OMIM 606,144), and EFNB1 (OMIM 300,035), to determine their participation in craniosynostosis in the Mexican population.

Extremely severe scoliosis, heterotopic ossification, and osteoarthritis in a three-generation family with Crouzon syndrome carrying a mutant c.799T>C FGFR2

Background

Crouzon syndrome is a rare and complex autosomal dominant craniosynostosis syndrome with a prevalence of approximately 1 in 60,000 births. The typical features are craniosynostosis, proptosis, midfacial hypoplasia, and noncranial manifestations, including deformities in the cervical spine, elbow, and fingers. Crouzon syndrome is usually caused by pathogenic variants in the fibroblast growth factor receptor 2 (FGFR2) gene.

Methods

We reported a three‐generation family with Crouzon syndrome; the proband showed extremely severe limb abnormalities. The clinical features were obtained by physical examination and radiographic examination. Sanger sequencing of all 18 exons of FGFR2 was conducted to identify the disease‐causing mutation.

Results

The proband was a 44‐year‐old man who showed characteristics of Crouzon syndrome, including craniofacial dysostosis, shallow orbits, proptosis, midface hypoplasia, beaked nose, strabismus, short superior lip, short stature, and neck injection. In addition to these typical characteristics, radiographic examination showed severe scoliosis, heterotopic ossification of the elbows, knee osteoarthritis, metacarpophalangeal joint valgus, collapse of the articular surface of the thumb metacarpal, knuckle ossification and fusion. Sanger sequencing identified a heterozygous pathogenic variant c.799T>C, p.(Ser267Pro) in exon 7 of FGFR2 in affected individuals.

Conclusion

Crouzon syndrome in this three‐generation family was caused by c.799T>C FGFR2, and the patient showed a different phenotypic appearance from other Crouzon patients with c.799T>C FGFR2.

Say-Barber-Biesecker-Young-Simpson syndrome and Genitopatellar syndrome: Lumping or splitting?

The Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome (SBBYSS) and Genitopatellar syndrome (GTPTS) are 2 rare but clinically well-described diseases caused by de novo heterozygous sequence variants in the KAT6B gene. Both phenotypes are characterized by significant global developmental delay/intellectual disability, hypotonia, genital abnormalities, and patellar hypoplasia/agenesis. In addition, congenital heart defects, dental abnormalities, hearing loss, and thyroid anomalies are common to both phenotypes. This broad clinical overlap led some authors to propose the concept of KAT6B spectrum disorders. On the other hand, some clinical features could help to differentiate the 2 disorders. Furthermore, it is possible to establish a genotype-phenotype correlation when considering the position of the sequence variant along the gene, supporting the notion of the 2 disorders as really distinct entities.

FGFR genes mutation is an independent prognostic factor and associated with lymph node metastasis in squamous non-small cell lung cancer

Targeting FGFRs is one of the most promising therapeutic strategies in squamous non-small cell lung cancer (SQCC). However, different FGFR genomic aberrations can be associated with distinct biological characteristics that result in different clinical outcomes or therapeutic consequences. Currently, the full spectrum of FGFR gene aberrations and their clinical significance in SQCC have not been comprehensively studied. Here, we used Next-generation sequencing to investigate the presence of FGFR gene mutations in 143 tumors from patients with stage I, II or III SQCC and who had not been treated with chemotherapy or radiotherapy prior to surgery. FGFR gene mutations were identified in 24 cases, resulting in an overall frequency of 16.9%. Among the mutations, 7% (10/143) were somatic mutations, and 9.8% (14/143) germline mutations. FGFR mutations were significantly associated with an increased risk of lymph node metastasis. SQCC patients with a FGFR somatic mutation had shorter OS (overall survival, log rank P = 0.005) and DFS (disease-free survival，log rank P = 0.004) compared with those without an FGFR mutation. The multivariate analysis confirmed that a somatic mutation was an independent poor prognostic factor for OS (HR: 4.26, 95% CI: 1.49-12.16, P = 0.007) and DFS (HR: 3.16, 95% CI: 1.20-8.35, P = 0.020). Our data indicate that FGFR genes mutation is an independent prognostic factor and associated with lymph node metastasis in stage I to III Chinese SQCC patients.

Craniosynostosis affects the majority of mucopolysaccharidosis patients and can contribute to increased intracranial pressure

BACKGROUND

The mucopolysaccharidoses are multisystem lysosomal storage diseases characterized by extensive skeletal deformities, including skull abnormalities. The objective of this study was to determine the incidence of craniosynostosis in the different mucopolysaccharidosis (MPS) types and its clinical consequences.

METHODS

In a prospective cohort study spanning 10 years, skull imaging and clinical evaluations were performed in 47 MPS patients (type I, II, VI, and VII). A total of 215 radiographs of the skull were analyzed. The presence and type of craniosynostosis, the sutures involved, progression over time, skull shape, head circumference, fundoscopy, and ventriculoperitoneal shunt (VPS) placement data were evaluated.

RESULTS

Craniosynostosis of at least one suture was present in 77% of all 47 MPS patients (≤ 6 years of age in 40% of all patients). In 32% of all MPS patients, premature closure of all sutures was seen (≤ 6 years of age in 13% of all patients). All patients with early closure had a more severe MPS phenotype, both in the neuronopathic (MPS I, II) and non-neuronopathic (MPS VI) patient groups. Because of symptomatic increased intracranial pressure (ICP), a VPS was placed in six patients, with craniosynostosis as a likely or certain causative factor for the increased pressure in four patients. One patient underwent cranial vault expansion because of severe craniosynostosis.

CONCLUSIONS

Craniosynostosis occurs in the majority of MPS patients. Since the clinical consequences can be severe and surgical intervention is possible, skull growth and signs and symptoms of increased ICP should be monitored in both neuronopathic and non-neuronopathic patients with MPS.

Genetic Causes of Craniosynostosis: An Update

In 1993, Jabs et al. were the first to describe a genetic origin of craniosynostosis. Since this discovery, the genetic causes of the most common syndromes have been described. In 2015, a total of 57 human genes were reported for which there had been evidence that mutations were causally related to craniosynostosis. Facilitated by rapid technological developments, many others have been identified since then. Reviewing the literature, we characterize the most common craniosynostosis syndromes followed by a description of the novel causes that were identified between January 2015 and December 2017.

Fibroblast Growth Factor Receptor 2 (FGFR2) Mutation Related Syndromic Craniosynostosis

Craniosynostosis results from the premature fusion of cranial sutures, with an incidence of 1 in 2,100-2,500 live births. The majority of cases are non-syndromic and involve single suture fusion, whereas syndromic cases often involve complex multiple suture fusion. The fibroblast growth factor receptor 2 (FGFR2) gene is perhaps the most extensively studied gene that is mutated in various craniosynostotic syndromes including Crouzon, Apert, Pfeiffer, Antley-Bixler, Beare-Stevenson cutis gyrata, Jackson-Weiss, Bent Bone Dysplasia, and Seathre-Chotzen-like syndromes. The majority of these mutations are missense mutations that result in constitutive activation of the receptor and downstream molecular pathways. Treatment involves a multidisciplinary approach with ultimate surgical fixation of the cranial deformity to prevent further sequelae. Understanding the molecular mechanisms has allowed for the investigation of different therapeutic agents that can potentially be used to prevent the disorders. Further research efforts are need to better understand screening and effective methods of early intervention and prevention. Herein, the authors provide a comprehensive update on FGFR2-related syndromic craniosynostosis.

Molecular Modeling and Functional Analysis of Exome Sequencing–Derived Variants of Unknown Significance Identify a Novel, Constitutively Active FGFR2 Mutant in Cholangiocarcinoma

Purpose

Genomic testing has increased the quantity of information available to oncologists. Unfortunately, many identified sequence alterations are variants of unknown significance (VUSs), which thus limit the clinician’s ability to use these findings to inform treatment. We applied a combination of in silico prediction and molecular modeling tools and laboratory techniques to rapidly define actionable VUSs.

Materials and Methods

Exome sequencing was conducted on 308 tumors from various origins. Most single nucleotide alterations within gene coding regions were VUSs. These VUSs were filtered to identify a subset of therapeutically targetable genes that were predicted with in silico tools to be altered in function by their variant sequence. A subset of receptor tyrosine kinase VUSs was characterized by laboratory comparison of each VUS versus its wild-type counterpart in terms of expression and signaling activity.

Results

The study identified 4,327 point mutations of which 3,833 were VUSs. Filtering for mutations in genes that were therapeutically targetable and predicted to affect protein function reduced these to 522 VUSs of interest, including a large number of kinases. Ten receptor tyrosine kinase VUSs were selected to explore in the laboratory. Of these, seven were found to be functionally altered. Three VUSs (FGFR2 F276C, FGFR4 R78H, and KDR G539R) showed increased basal or ligand-stimulated ERK phosphorylation compared with their wild-type counterparts, which suggests that they support transformation. Treatment of a patient who carried FGFR2 F276C with an FGFR inhibitor resulted in significant and sustained tumor response with clinical benefit.

Conclusion

The findings demonstrate the feasibility of rapid identification of the biologic relevance of somatic mutations, which thus advances clinicians’ ability to make informed treatment decisions.

Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome

Auriculocondylar syndrome, mainly characterized by micrognathia, small mandibular condyle, and question mark ears, is a rare disease segregating in an autosomal dominant pattern in the majority of the families reported in the literature. So far, pathogenic variants in PLCB4, GNAI3, and EDN1 have been associated with this syndrome. It is caused by a developmental abnormality of the first and second pharyngeal arches and it is associated with great inter- and intra-familial clinical variability, with some patients not presenting the typical phenotype of the syndrome. Moreover, only a few patients of each molecular subtype of Auriculocondylar syndrome have been reported and sequenced. Therefore, the spectrum of clinical and genetic variability is still not defined. In order to address these questions, we searched for alterations in PLCB4, GNAI3, and EDN1 in patients with typical Auriculocondylar syndrome (n = 3), Pierre Robin sequence-plus (n = 3), micrognathia with additional craniofacial malformations (n = 4), or non-specific auricular dysplasia (n = 1), which could represent subtypes of Auriculocondylar syndrome. We found novel pathogenic variants in PLCB4 only in two of three index patients with typical Auriculocondylar syndrome. We also performed a detailed comparative analysis of the patients presented in this study with those previously published, which showed that the pattern of auricular abnormality and full cheeks were associated with molecularly characterized individuals with Auriculocondylar syndrome. Finally, our data contribute to a better definition of a set of parameters for clinical classification that may be used as a guidance for geneticists ordering molecular testing for Auriculocondylar syndrome. © 2017 Wiley Periodicals, Inc.

C278F mutation in FGFR2 gene causes two different types of syndromic craniosynostosis in two Chinese patients

The current study was performed with aim to investigate the fibroblast growth factor receptor 2 (FGFR2) gene in two Chinese families with two different forms of syndromic craniosynostosis, and to characterize their associated clinical features. Two families underwent complete ophthalmic examinations, and two patients from each family were diagnosed with craniosynostosis. Genomic DNA was extracted from leukocytes of peripheral blood collected from these two families and from 200 unrelated subjects within the same population as controls. Exons 8 and 10 of the FGFR2 gene were amplified by polymerase chain reaction and directly sequenced. Ophthalmic examinations of the two patients revealed shallow orbits and ocular proptosis, accompanied by midface hypoplasia and craniosynostosis. Case 1 had retinal detachment, abnormal limbs and hands, while case 2 exhibited normal hands and feet upon clinical examination. A heterozygous FGFR2 missense mutation c.833G>T (C278F) in exon 8 was identified in these two patients, but not in unaffected family members or the normal controls. Although FGFR2 gene mutations and polymorphisms have been studied in various ethnic groups, we report a mutation of FGFR2 in two different Chinese patients with two different types of syndromic craniosynostosis.

Multidisciplinary care of craniosynostosis

The management of craniosynostosis, especially in the setting of craniofacial syndromes, is ideally done in a multidisciplinary clinic with a team focused toward comprehensive care. Craniosynostosis is a congenital disorder of the cranium, caused by the premature fusion of one or more cranial sutures. This fusion results in abnormal cranial growth due to the inability of the involved sutures to accommodate the growing brain. Skull growth occurs only at the patent sutures, resulting in an abnormal head shape. If cranial growth is severely restricted, as seen in multisuture craniosynostosis, elevation in intracranial pressure can occur. Whereas most patients treated in a multidisciplinary craniofacial clinic have non-syndromic or isolated craniosynostosis, the most challenging patients are those with syndromic craniosynostosis. The purpose of this article was to discuss the multidisciplinary team care required to treat both syndromic and non-syndromic craniosynostosis.

Mutation c.943G>T (p.Ala315Ser) in FGFR2 Causing a Mild Phenotype of Crouzon Craniofacial Dysostosis in a Three-Generation Family

Crouzon syndrome craniofacial dysostosis type I [OMIM 123500] is caused by mutations in the gene encoding fibroblast growth factor receptor-2 (FGFR2). An overlapping phenotype with Muenke and Crouzon syndrome with acanthosis nigricans (FGFR3 mutations) is known. The clinical diagnosis can be corroborated by molecular studies in about 80-90% of the cases. No clear genotype/phenotype correlation has been identified yet. Here, we describe a second family with a mild phenotype in which the FGFR2 mutation c.943G>T leading to the amino acid substitution p.Ala315Ser was detected. Five affected family members showed craniofacial dysostosis without overt craniosynostosis. They all had midface hypoplasia. Crouzonoid appearance with mild protrusion of bulbi was only apparent in our index patient as well as obstructive sleep apnea episodes leading to reduced oxygen saturation; therefore, surgical intervention was suggested. One other affected family member additionally had iris coloboma.

Mutation analysis of FGFR1-3 in 11 Japanese patients with syndromic craniosynostoses

Syndromic craniosynostoses usually occur as single gene disorders. In this study, we analyzed FGFR1-3 genes in four patients with Crouzon syndrome (CS), four patients with Pfeiffer syndrome type 2 (PS-2), one patient with Jackson-Weiss syndrome (JWS), and two patients (sisters) with Muenke syndrome (MS). FGFR2 and FGFR3 mutations were identified in 10 of the 11 patients. Notably, we found a novel FGFR2 p.Asn549Thr mutation in a patient with CS, and a novel FGFR2 p.Ser347Cys mutation in a patient with JWS (thus, this patient was turned out to have an FGFR2-related PS-variant). We also identified an FGFR2 p.Ser252Leu mutation in a phenotypically normal father of a daughter with CS, and an FGFR3 p.Pro250Arg mutation in a mildly macrocephalic father of sisters with MS. These findings, together with previous data, imply that the same FGFR2 mutations can be associated with a wide range of phenotypes including clinically different forms of syndromic craniosynostosis and apparently normal phenotype, depending on other (epi)genetic and environmental factors. Thus, genetic studies are recommended not only for obviously affected individuals but also for family members with apparently normal phenotype or non-specific subtle abnormal phenotype, to allow for pertinent genetic counseling. © 2016 Wiley Periodicals, Inc.

Pathogenic Cysteine Removal Mutations in FGFR Extracellular Domains Stabilize Receptor Dimers and Perturb the TM Dimer Structure

Missense mutations that introduce or remove cysteine residues in receptor tyrosine kinases are believed to cause pathologies by stabilizing the active receptor tyrosine kinase dimers. However, the magnitude of this stabilizing effect has not been measured for full-length receptors. Here, we characterize the dimer stabilities of three full-length fibroblast growth factor receptor (FGFR) mutants harboring pathogenic cysteine substitutions: the C178S FGFR1 mutant, the C342R FGFR2 mutant, and the C228R FGFR3 mutant. We find that the three mutations stabilize the FGFR dimers. We further see that the mutations alter the configuration of the FGFR transmembrane dimers. Thus, both aberrant dimerization and perturbed dimer structure likely contribute to the pathological phenotypes arising due to these mutations.

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.

Understanding craniosynostosis as a growth disorder

Craniosynostosis is a condition of complex etiology that always involves the premature fusion of one or multiple cranial sutures and includes various anomalies of the soft and hard tissues of the head. Steady progress in the field has resulted in identifying gene mutations that recurrently cause craniosynostosis. There are now scores of mutations on many genes causally related to craniosynostosis syndromes, though the genetic basis for the majority of nonsyndromic cases is unknown. Identification of these genetic mutations has allowed significant progress in understanding the intrinsic properties of cranial sutures, including mechanisms responsible for normal suture patency and for pathogenesis of premature suture closure. An understanding of morphogenesis of cranial vault sutures is critical to understanding the pathophysiology of craniosynostosis conditions, but the field is now poised to recognize the repeated changes in additional skeletal and soft tissues of the head that typically accompany premature suture closure. We review the research that has brought an understanding of premature suture closure within our reach. We then enumerate the less well-studied, but equally challenging, nonsutural phenotypes of craniosynostosis conditions that are well characterized in available mouse models. We consider craniosynostosis as a complex growth disorder of multiple tissues of the developing head, whose growth is also targeted by identified mutations in ways that are poorly understood. Knowledge gained from studies of humans and mouse models for these conditions underscores the diverse, associated developmental anomalies of the head that contribute to the complex phenotypes of craniosynostosis conditions presenting novel challenges for future research. WIREs Dev Biol 2016, 5:429-459. doi: 10.1002/wdev.227 For further resources related to this article, please visit the WIREs website.

Mutational patterns in oncogenes and tumour suppressors

All cancers depend upon mutations in critical genes, which confer a selective advantage to the tumour cell. Knowledge of these mutations is crucial to understanding the biology of cancer initiation and progression, and to the development of targeted therapeutic strategies. The key to understanding the contribution of a disease-associated mutation to the development and progression of cancer, comes from an understanding of the consequences of that mutation on the function of the affected protein, and the impact on the pathways in which that protein is involved. In this paper we examine the mutation patterns observed in oncogenes and tumour suppressors, and discuss different approaches that have been developed to identify driver mutations within cancers that contribute to the disease progress. We also discuss the MOKCa database where we have developed an automatic pipeline that structurally and functionally annotates all proteins from the human proteome that are mutated in cancer.

Tracheal cartilaginous sleeves in children with syndromic craniosynostosis

PURPOSE

Because a tracheal cartilaginous sleeve (TCS) confers a significant mortality risk that can be mitigated with appropriate intervention, we sought to describe the prevalence and associated genotypes in a large cohort of children with syndromic craniosynostosis.

METHODS

Chart review of patients with syndromic craniosynostosis across two institutions.

RESULTS

In a cohort of 86 patients with syndromic craniosynostosis, 31 required airway evaluation under anesthesia. TCS was found in 19, for an overall prevalence of 22%. FGFR2, TWIST1, and FGFR3 mutations were identified in children with TCS. All five children with a W290C mutation in FGFR2 had TCS, and most previously reported children with W290C had identification of TCS or early death. In contrast, TCS was not associated with other mutations at residue 290.

CONCLUSION

There is an association between TCS and syndromic craniosynostosis, and it appears to be particularly high in individuals with the W290C mutation in FGFR2. Referral to a pediatric otolaryngologist and consideration of operative airway evaluation (i.e., bronchoscopy or rigid endoscopy) in all patients with syndromic craniosynostosis should be considered to evaluate for TCS. Results from genetic testing may help providers weigh the risks and benefits of early airway evaluation and intervention in children with higher-risk genotypes.Genet Med 19 1, 62-68.

Apert and Crouzon syndromes-Cognitive development, brain abnormalities, and molecular aspects

Apert and Crouzon are the most common craniosynostosis syndromes associated with mutations in the fibroblast growth factor receptor 2 (FGFR2) gene. We conducted a study to examine the molecular biology, brain abnormalities, and cognitive development of individuals with these syndromes. A retrospective longitudinal review of 14 patients with Apert and Crouzon syndromes seen at the outpatient Craniofacial Surgery Hospital for Rehabilitation of Craniofacial Anomalies in Brazil from January 1999 through August 2010 was performed. Patients between 11 and 36 years of age (mean 18.29 ± 5.80), received cognitive evaluations, cerebral magnetic resonance imaging, and molecular DNA analyses. Eight patients with Apert syndrome (AS) had full scale intelligence quotients (FSIQs) that ranged from 47 to 108 (mean 76.9 ± 20.2), and structural brain abnormalities were identified in five of eight patients. Six patients presented with a gain-of-function mutation (p.Ser252Trp) in FGFR2 and FSIQs in those patients ranged from 47 to78 (mean 67.2 ± 10.7). One patient with a gain-of-function mutation (p.Pro253Arg) had a FSIQ of 108 and another patient with an atypical splice mutation (940-2A →G) had a FSIQ of 104. Six patients with Crouzon syndrome had with mutations in exons IIIa and IIIc of FGFR2 and their FSIQs ranged from 82 to 102 (mean 93.5 ± 6.7). These reveal that molecular aspects are another factor that can be considered in studies of global and cognitive development of patients with Apert and Crouzon syndrome (CS). © 2016 Wiley Periodicals, Inc.

A Patient With Pansynostosis and Williams-Beuren Syndrome

BACKGROUND

Williams-Beuren syndrome (WBS) is a multisystemic genetic disorder caused by a gene deletion at gene locus 7q11.23. This article presents the first described case of a patient with WBS and simultaneous pansynostosis.

CASE PRESENTATION

This article presents the management of this young Caucasian boy from birth until the age of 12 years and provides an overview of previously described manifestations of WBS in the craniofacial region.

CONCLUSIONS

This case demonstrates the surgical treatment of pansynostosis in a child with WBS and might provide interesting aspects in the diagnostics and management of this rare malformation.

Altered FGF signalling in congenital craniofacial and skeletal disorders

The fibroblast growth factor (FGF) signalling pathway has been the focus of intense genetic and functional research for several decades. The emerging data implicate FGF signalling in diverse regulatory processes, both in the developing embryo as well as in the adult organism. Alterations in this tightly regulated pathway can lead to a number of pathological conditions, ranging from well-recognized congenital disorders to cancer. In order to mediate their cellular processes, FGFs signal through a subfamily of tyrosine kinase receptors, called FGF receptors (FGFRs). In humans, four FGFRs are described, and, to date, mutations in FGFR1, FGFR2, and FGFR3 have been shown to underlie human developmental disorders. FGFs/FGFRs are known to be key players in both endochondral and intramembranous bone development. In this review, we focus on the major developmental craniofacial and skeletal disorders which result from altered FGF signalling.

Effects of FGFR Signaling on Cell Proliferation and Differentiation of Apert Dental Cells

The Apert syndrome is a rare congenital disorder most often arising from S252W or P253R mutations in fibroblast growth factor receptor (FGFR2). Numerous studies have focused on the regulatory role of Apert FGFR2 signaling in bone formation, whereas its functional role in tooth development is largely unknown. To investigate the role of FGFR signaling in cell proliferation and odontogenic differentiation of human dental cells in vitro, we isolated dental pulp and enamel organ epithelia (EOE) tissues from an Apert patient carrying the S252W FGFR2 mutation. Apert primary pulp and EOE cells were established and shown to exhibit normal morphology and express alkaline phosphatase under differentiation conditions. Similar to control cells, Apert dental pulp and EOE cells expressed all FGFRs, with highest levels of FGFR1 followed by FGFR2 and low levels of FGFR3 and FGFR4. However, Apert cells had increased cell growth compared with control cells. Distinct from previous findings in osteoblast cells, gain-of-function S252W FGFR2 mutation did not upregulate the expression of epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFRα), but elevated extracellular signal-regulated kinase (ERK) signaling in cells after EGF stimulation. Unexpectedly, there was little effect of the S252W mutation on odontogenic gene expression in dental pulp and EOE cells. However, after inhibition of total FGFR signaling or ERK signaling, the expression of odontogenic genes was upregulated in both dental cell types, indicating the negative effect of whole FGFR signaling on odontogenic differentiation. This study provides novel insights on FGFR signaling and a common Apert FGFR2 mutation in the regulation of odontogenic differentiation of dental mesenchymal and epithelial cells.

FGFR2 mutation in 46,XY sex reversal with craniosynostosis

Patients with 46,XY gonadal dysgenesis (GD) exhibit genital anomalies, which range from hypospadias to complete male-to-female sex reversal. However, a molecular diagnosis is made in only 30% of cases. Heterozygous mutations in the human FGFR2 gene cause various craniosynostosis syndromes including Crouzon and Pfeiffer, but testicular defects were not reported. Here, we describe a patient whose features we would suggest represent a new FGFR2-related syndrome, craniosynostosis with XY male-to-female sex reversal or CSR. The craniosynostosis patient was chromosomally XY, but presented as a phenotypic female due to complete GD. DNA sequencing identified the FGFR2c heterozygous missense mutation, c.1025G>C (p.Cys342Ser). Substitution of Cys342 by Ser or other amino acids (Arg/Phe/Try/Tyr) has been previously reported in Crouzon and Pfeiffer syndrome. We show that the 'knock-in' Crouzon mouse model Fgfr2c(C342Y/C342Y) carrying a Cys342Tyr substitution displays XY gonadal sex reversal with variable expressivity. We also show that despite FGFR2c-Cys342Tyr being widely considered a gain-of-function mutation, Cys342Tyr substitution in the gonad leads to loss of function, as demonstrated by sex reversal in Fgfr2c(C342Y/-) mice carrying the knock-in allele on a null background. The rarity of our patient suggests the influence of modifier genes which exacerbated the testicular phenotype. Indeed, patient whole exome analysis revealed several potential modifiers expressed in Sertoli cells at the time of testis determination in mice. In summary, this study identifies the first FGFR2 mutation in a 46,XY GD patient. We conclude that, in certain rare genetic contexts, maintaining normal levels of FGFR2 signaling is important for human testis determination.

A Genetic-Pathophysiological Framework for Craniosynostosis

Craniosynostosis, the premature fusion of one or more cranial sutures of the skull, provides a paradigm for investigating the interplay of genetic and environmental factors leading to malformation. Over the past 20 years molecular genetic techniques have provided a new approach to dissect the underlying causes; success has mostly come from investigation of clinical samples, and recent advances in high-throughput DNA sequencing have dramatically enhanced the study of the human as the preferred "model organism." In parallel, however, we need a pathogenetic classification to describe the pathways and processes that lead to cranial suture fusion. Given the prenatal onset of most craniosynostosis, investigation of mechanisms requires more conventional model organisms; principally the mouse, because of similarities in cranial suture development. We present a framework for classifying genetic causes of craniosynostosis based on current understanding of cranial suture biology and molecular and developmental pathogenesis. Of note, few pathologies result from complete loss of gene function. Instead, biochemical mechanisms involving haploinsufficiency, dominant gain-of-function and recessive hypomorphic mutations, and an unusual X-linked cellular interference process have all been implicated. Although few of the genes involved could have been predicted based on expression patterns alone (because the genes play much wider roles in embryonic development or cellular homeostasis), we argue that they fit into a limited number of functional modules active at different stages of cranial suture development. This provides a useful approach both when defining the potential role of new candidate genes in craniosynostosis and, potentially, for devising pharmacological approaches to therapy.

Clinical and genetic characteristics of craniosynostosis in Hungary

Craniosynostosis, the premature closure of cranial sutures, is a common craniofacial disorder with heterogeneous etiology and appearance. The purpose of this study was to investigate the clinical and molecular characteristics of craniosynostoses in Hungary, including the classification of patients and the genetic analysis of the syndromic forms. Between 2006 and 2012, 200 patients with craniosynostosis were studied. Classification was based on the suture(s) involved and the associated clinical features. In syndromic cases, genetic analyses, including mutational screening of the hotspot regions of the FGFR1, FGFR2, FGFR3, and TWIST1 genes, karyotyping and FISH study of TWIST1, were performed. The majority (88%) of all patients with craniosynostosis were nonsyndromic. The sagittal suture was most commonly involved, followed by the coronal, metopic, and lambdoid sutures. Male, twin gestation, and very low birth weight were risk factors for craniosynostosis. Syndromic craniosynostosis was detected in 24 patients. In 17 of these patients, Apert, Crouzon, Pfeiffer, Muenke, or Saethre-Chotzen syndromes were identified. In one patient, multiple-suture craniosynostosis was associated with achondroplasia. Clinical signs were not typical for any particular syndrome in six patients. Genetic abnormalities were detected in 18 syndromic patients and in 8 relatives. In addition to 10 different, known mutations in FGFR1,FGFR2 or FGFR3, one novel missense mutation, c.528C>G(p.Ser176Arg), was detected in the TWIST1 gene of a patient with Saethre-Chotzen syndrome. Our results indicate that detailed clinical assessment is of paramount importance in the classification of patients and allows indication of targeted molecular testing with the highest possible diagnostic yield.