Pro250Arg Mutation Research Articles

Muencke Syndrome With Cleft Lip and Palate

Muencke syndrome results from mutations in the FGFR3 gene, and although it is well recognized that the clinical presentation is variable, the important key finding includes coronal synostosis. We present a family where a mother with proven FGFR3 Pro250Arg mutation gave birth to identical twins both of whom had craniosynostosis but had coexisting bilateral cleft lip and palate. We believe that this is the first description of clefting occurring in conjunction with Muencke syndrome and so further extends the range of phenotypic variation that can occur in this syndrome.

Muenke Syndrome Associated With Multiple Osteochondromas

Muenke syndrome caused by the FGFR3 Pro250Arg mutation is associated with craniosynostosis, hearing loss, and various bony anomalies. Although this mutation is involved in bone growth and development, bony tumors are rare in this condition. We describe a patient with a molecular diagnosis of Muenke syndrome who also presented with multiple osteochondromas of the upper and lower extremities. This association has only been described once before in a patient with an isolated osteochondroma of the proximal tibia. Altered expression of FGFR3, an important mediator of chondrocyte proliferation and differentiation during in the growth plates of long bones, may help to explain the development of osteochondromatous lesions in this patient.

Additional Phenotypic Features of Muenke Syndrome in 2 Dutch Families

In about 30% of the patients with syndromal craniosynostosis, a genetic mutation can be traced. For the purpose of adequate genetic counseling and treatment of these patients, the full spectrum of clinical findings for each specific mutation needs to be appreciated. The Pro250Arg mutation in the FGFR3 gene is found in patients with Muenke syndrome and is one of the most frequently encountered mutations in craniosynostosis syndromes. A number of studies on the relationship between genotype and phenotype concerning this specific mutation have been published. Two Dutch families with Muenke syndrome were screened for the reported characteristics of this syndrome and for additional features. New phenotypical findings were hypoplasia of the frontal sinus, ptosis of the upper eyelids, dysplastic elbow joints with restricted elbow motion, and mild cutaneous syndactyly. Incidentally, polydactyly, severe ankylosis of the elbow, fusion of cervical vertebrae, and epilepsy were found. Upper eyelid ptosis is thought to be pathognomonic for Saethre-Chotzen syndrome but was also observed in our series of patients with Muenke syndrome. Because Muenke and Saethre-Chotzen syndrome can have similar phenotypes, DNA analysis is needed to distinguish between these syndromes, even when a syndrome diagnosis is already made in a family member.

A Child With an FGFR3 Mutation, a Laterality Disorder and an Hepatoblastoma: Novel Associations and Possible Gene–Environment Interactions

We report on a 3-year-old girl, from a 3-generation family with an FGFR3 Pro250Arg mutation, who in addition to craniosynostosis, had a laterality disorder and hepatoblastoma, following a pregnancy complicated by maternal insulin-dependent diabetes. The clinical features possibly result from the combined effects of the maternal diabetes and the familial FGFR3 mutation, thus representing a unique gene-environment interaction that may have implications for the understanding of the phenotypes described in this child.

Dynamic morphological changes in the skulls of mice mimicking human Apert syndrome resulting from gain‐of‐function mutation of FGFR2 (P253R)

Apert syndrome is caused mainly by gain-of-function mutations of fibroblast growth factor receptor 2. We have generated a mouse model (Fgfr2(+/P253R)) mimicking human Apert syndrome resulting from fibroblast growth factor receptor 2 Pro253Arg mutation using the knock-in approach. This mouse model in general has the characteristic skull morphology similar to that in humans with Apert syndrome. To characterize the detailed changes of form in the overall skull and its major anatomic structures, euclidean distance matrix analysis was used to quantitatively compare the form and growth difference between the skulls of mutants and their wild-type controls. There were substantial morphological differences between the skulls of mutants and their controls at 4 and 8 weeks of age (P < 0.01). The mutants showed shortened skull dimensions along the rostrocaudal axis, especially in their face. The width of the frontal bone and the distance between the two orbits were broadened mediolaterally. The neurocrania were significantly increased along the dorsoventral axis and slightly increased along the mediolateral axis, and also had anteriorly displayed opisthion along the rostrocaudal axis. Compared with wild-type, the mutant mandible had an anteriorly displaced coronoid process and mandibular condyle along the rostrocaudal axis. We further found that there was catch-up growth in the nasal bone, maxilla, zygomatic bone and some regions of the mandible of the mutant skulls during the 4-8-week interval. The above-mentioned findings further validate the Fgfr2(+/P253R) mouse strain as a good model for human Apert syndrome. The changes in form characterized in this study will help to elucidate the mechanisms through which the Pro253Arg mutation in fibroblast growth factor receptor 2 affects craniofacial development and causes Apert syndrome.

A Korean Family with the Muenke Syndrome

The Muenke syndrome (MS) is characterized by unicoronal or bicoronal craniosynostosis, midfacial hypoplasia, ocular hypertelorism, and a variety of minor abnormalities associated with a mutation in the fibroblast growth factor receptor 3 (FGFR3) gene. The birth prevalence is approximately one in 10,000 live births, accounting for 8-10% of patients with coronal synostosis. Although MS is a relatively common diagnosis in patients with craniosynostosis syndromes, with autosomal dominant inheritance, there has been no report of MS, in an affected Korean family with typical cephalo-facial morphology that has been confirmed by molecular studies. Here, we report a familial case of MS in a female patient with a Pro250Arg mutation in exon 7 (IgII-IGIII linker domain) of the FGFR3 gene. This patient had mild midfacial hypoplasia, hypertelorism, downslanting palpebral fissures, a beak shaped nose, plagio-brachycephaly, and mild neurodevelopmental delay. The same mutation was confirmed in the patient's mother, two of the mother's sisters and the maternal grandfather. The severity of the cephalo-facial anomalies was variable among these family members.

A Pro253Arg mutation in fibroblast growth factor receptor 2 (Fgfr2) causes skeleton malformation mimicking human Apert syndrome by affecting both chondrogenesis and osteogenesis

Apert syndrome is one of the most severe craniosynostosis that is mainly caused by either a Ser252Trp(S252W) or Pro253Arg(P253R) mutation in fibroblast growth factor receptor 2 (FGFR2). As an autosomal dominant disorder, Apert syndrome is mainly characterized by skull malformation resulting from premature fusion of craniofacial sutures, as well as syndactyly, etc. A P253R mutation of FGFR2 results in nearly one-thirds of the cases of Apert syndrome. The pathogenesis of Apert syndrome resulting from P253R mutation of FGFR2 is still not fully understood. Here we reported a knock-in mouse model carrying P253R mutation in Fgfr2. The mutant mice exhibit smaller body size and brachycephaly. Analysis of the mutant skulls and long bones revealed premature fusion of coronal suture, shortened cranial base and growth plates of long bones. In vitro organ culture studies further revealed that, compared with wild-type littermates, the mutant mice have prematurely fused coronal sutures and retarded long bone growth. Treatment of the cultured calvaria and femur with PD98059, an Erk1/2 inhibitor, resulted in partially alleviated coronal suture fusion and growth retardation of femur respectively. Our data indicated that the P253R mutation in Fgfr2 directly affect intramembranous and endochondral ossification, which resulted in the premature closure of coronal sutures and growth retardation of long bones and cranial base. And the Erk1/2 signaling pathway partially mediated the effects of P253R mutation of Fgfr2 on cranial sutures and long bones.

Muenke syndrome (FGFR3‐related craniosynostosis): Expansion of the phenotype and review of the literature

Muenke syndrome is an autosomal dominant disorder characterized by coronal suture craniosynostosis, hearing loss, developmental delay, carpal and tarsal fusions, and the presence of the Pro250Arg mutation in the FGFR3 gene. Reduced penetrance and variable expressivity contribute to the wide spectrum of clinical findings in Muenke syndrome. To better define the clinical features of this syndrome, we initiated a study of the natural history of Muenke syndrome. To date, we have conducted a standardized evaluation of nine patients with a confirmed Pro250Arg mutation in FGFR3. We reviewed audiograms from an additional 13 patients with Muenke syndrome. A majority of the patients (95%) demonstrated a mild-to-moderate, low frequency sensorineural hearing loss. This pattern of hearing loss was not previously recognized as characteristic of Muenke syndrome. We also report on feeding and swallowing difficulties in children with Muenke syndrome. Combining 312 reported cases of Muenke syndrome with data from the nine NIH patients, we found that females with the Pro250Arg mutation were significantly more likely to be reported with craniosynostosis than males (P < 0.01). Based on our findings, we propose that the clinical management should include audiometric and developmental assessment in addition to standard clinical care and appropriate genetic counseling.

FGF2 effects in periosteal fibroblasts bearing the FGFR2 receptor Pro253 Arg mutation

Aim: A growing number of mutations mapped in the receptor gene for fibroblast growth factor have been implicated in several cranial development disorders including the Apert and Crouzon syndromes. The present paper investigated cellular mechanisms underlying Apert phenotype, by analyzing the effects of FGF2 in primary cultures of Apert periosteal fibroblasts carrying the FGFR2 Pro253Arg mutation. Results: FGF2 administration significantly decreased extracellular matrix production in mutant cells by stimulating degradative enzymatic activities. Gene expression analysis revealed that decorin and biglycan, two proteoglycans involved in collagen fibrillogenesis, were more expressed in mutant cells and down-regulated by FGF2. FGF2 receptor binding showed little differences in high affinity receptor counts between mutant and wild-type cells, while we showed for the first time that low affinity receptors are significantly fewer in mutant cells. Differences were found in Crouzon syndrome, where both high and low affinity receptor counts were up-regulated. Conclusions: The different mutation and low affinity receptor regulation in mutant receptors support the hypothesis that the impact on the activity of the ligand–receptor complex could allow distinct modes of FGF2 activation in Apert and Crouzon syndromes, which interfere with the FGFR2 signalling cascade.

Differential Effects of FGFR2 Mutation in Ophthalmic Findings in Apert Syndrome

Apert syndrome is mostly caused by one of the two specific point mutations in the fibroblast growth factor receptor 2 (FGFR2). The objective of this study was to determine whether there were any differences in the prevalence of ophthalmic features in Apert syndrome when comparing the Ser252Trp and Pro253Arg mutations in FGFR2. This was a retrospective study of patients with Apert syndrome with genotype analysis. The prevalence of five ophthalmic features, visual impairment, amblyopia, strabismus, corneal abnormality, and pale optic discs, were compared between the two FGFR2 genotypes. There were 25 (74%) cases with Ser252Trp mutation, and 9 (26%) cases with the Pro253Arg mutation in FGFR2. Ophthalmic findings in 20 cases of FGFR2 Ser252Trp and 9 cases of Pro253Arg mutation were compared. Visual acuity worse than 6/12 in at least one eye was present in 60% patients with FGFR2 Ser252Trp mutation compared with 12.5% patients with Pro253Arg mutation (P < 0.05). Forty percent of eyes with FGFR2 Ser252Trp mutation compared with 12.5% eyes with Pro253Arg mutation were worse than 6/12. There was a trend of more frequent amblyopia and strabismus in FGFR2 Ser252Trp mutation and more frequent optic disc pallor in the FGFR2 Pro253Arg mutation. There was a differential effect of FGFR2 mutations in ophthalmic findings in patients with Apert syndrome, with significantly greater prevalence of visual impairment in the Ser252Trp mutation compared with the Pro253Arg mutation. Further study would elucidate whether the trends in differential effects between the two mutations in amblyopia, strabismus, and optic disc pallor represent real differences.

Trigonocephaly in Muenke syndrome

Saethre-Chotzen syndrome is caused by mutations in the TWIST gene on chromosome 7p21.2. However, Muenke et al. [(1997); Am J Hum Genet 91: 555-564] described a new subgroup carrying the Pro250Arg mutation in the fibroblast growth factor receptor (FGFR) 3 gene on chromosome 4p16. Uni or bicoronal synostosis appears to be the main clinical finding in both syndromes. We observed trigonocephaly as a new manifestation in Muenke syndrome. As a consequence we advise to routinely perform mutation analysis of the FGFR1, 2, and 3 genes in children with non-syndromic trigonocephaly.

Saethre–Chotzen syndrome caused by TWIST 1 gene mutations: functional differentiation from Muenke coronal synostosis syndrome

The Saethre-Chotzen syndrome (SCS) is an autosomal dominant craniosynostosis syndrome with uni- or bilateral coronal synostosis and mild limb deformities. It is caused by loss-of-function mutations of the TWIST 1 gene. In an attempt to delineate functional features separating SCS from Muenke's syndrome, we screened patients presenting with coronal suture synostosis for mutations in the TWIST 1 gene, and for the Pro250Arg mutation in FGFR3. Within a total of 124 independent pedigrees, 39 (71 patients) were identified to carry 25 different mutations of TWIST 1 including 14 novel mutations, to which six whole gene deletions were added. The 71 patients were compared with 42 subjects from 24 pedigrees carrying the Pro250Arg mutation in FGFR3 and 65 subjects from 61 pedigrees without a detectable mutation. Classical SCS associated with a TWIST 1 mutation could be separated phenotypically from the Muenke phenotype on the basis of the following features: low-set frontal hairline, gross ptosis of eyelids, subnormal ear length, dilated parietal foramina, interdigital webbing, and hallux valgus or broad great toe with bifid distal phalanx. Functional differences were even more important: intracranial hypertension as a consequence of early progressive multisutural fusion was a significant problem in SCS only, while mental delay and sensorineural hearing loss were associated with the Muenke's syndrome. Contrary to previous reports, SCS patients with complete loss of one TWIST allele showed normal mental development.

FGFR3 P250R Mutation Increases the Risk of Reoperation in Apparent ‘Nonsyndromic’ Coronal Craniosynostosis

Many patients with a clinical diagnosis of "nonsyndromic" coronal craniosynostosis have been found to be heterozygous for the fibroblast growth factor receptor 3 (FGFR3) mutation Pro250Arg. The phenotype associated with this mutation is variable and lacks highly distinctive features, so it is difficult to diagnose on clinical examination alone. The authors present a retrospective study of 76 patients with isolated coronal synostosis who were operated on in a single dedicated craniofacial unit over 25 years. The authors investigated whether any single factor, including the presence of a FGFR3 Pro250Arg mutation, predisposed to an increased transcranial reoperation rate. Eight patients had repeat transcranial surgery for a functional indication. Heterozygosity for the FGFR3 Pro250Arg mutation, present in 29 patients in the cohort, was the only factor found to have a significant association (P=0.048) with the transcranial reoperation rate. Six patients (20.7%) with the mutation underwent reoperation on the basis of raised intracranial pressure, as compared with two patients (4.3%) without the mutation. This highlights the need for genetic analysis and long-term clinical follow-up in apparently "isolated" coronal synostosis.

Negative autoregulation of fibroblast growth factor receptor 2 expression characterizing cranial development in cases of Apert (P253R mutation) and Pfeiffer (C278F mutation) syndromes and suggesting a basis for differences in their cranial phenotypes.

Heterogeneous mutations in the fibroblast growth factor receptor 2 gene (FGFR2) cause a range of craniosynostosis syndromes. The specificity of the Apert syndrome-affected cranial phenotype reflects its narrow mutational range: 98% of cases of Apert syndrome result from an Ser252Trp or Pro253Arg mutation in the immunoglobulin-like (Ig)IIIa extracellular subdomain of FGFR2. In contrast, a broad range of mutations throughout the extracellular domain of FGFR2 causes the overlapping cranial phenotypes of Pfeiffer and Crouzon syndromes and related craniofacial dysostoses. In this paper the expression of FGFR1, the IgIIIa/c and IgIIIa/b isoforms of FGFR2, and FGFR3 is investigated in Apert syndrome (P253R mutation)- and Pfeiffer syndrome (C278F mutation)-affected fetal cranial tissue and is contrasted with healthy human control tissues. Both FGFR1 and FGFR3 are normally expressed in the differentiated osteoblasts of the periosteum and osteoid, in domains overlapped by that of FGFR2, which widely include preosseous cranial mesenchyme. Expression of FGFR2, however, is restricted to domains of advanced osseous differentiation in both Apert syndrome- and Pfeiffer syndrome-affected cranial skeletogenesis in the presence of fibroblast growth factor (FGF)2, but not in the presence of FGF4 or FGF7. Whereas expression of the FGFR2-IgIIIa/b (KGFR) isoform is restricted in normal human cranial osteogenesis, there is preliminary evidence that KGFR is ectopically expressed in Pfeiffer syndrome-affected cranial osteogenesis. Contraction of the FGFR2-IgIIIa/c (BEK) expression domain in cases of Apert syndrome- and Pfeiffer syndrome-affected fetal cranial ossification suggests that the mutant activation of this receptor, by ligand-dependent or ligand-independent means, results in negative autoregulation. This phenomenon, resulting from different mechanisms in the two syndromes, offers a model by which to explain differences in their cranial phenotypes.

Sequence analyses and comparative modeling of fly and worm fibroblast growth factor receptors indicate that the determinants for FGF and heparin binding are retained in evolution

The presence of a large number of fibroblast growth factors (FGFs) and multiple splice forms of their receptors (FGFRs) in higher vertebrates makes the three-dimensional (3D) analysis of FGF interactions with their receptors a formidable task. The situation differs in Caenorhabditis elegans (worm) and Drosophila melanogaster (fruit fly), where only one or two FGF and FGFR sequences have been identified. Structural studies of the FGF–FGFR complexes in such primitive organisms should reveal the basic features of the ligand–receptor interactions as they first emerged through evolution. We have analysed the sequences of worm and fly FGFs and FGFRs and used the recently determined crystal structure of the human FGF1–FGFR2–heparin ternary complex [Pellegrini, L., Burke, D.F., von Delft, F., Mulloy, B. and Blundell, T.L. (2000) Nature 407, 1029–34] to construct 3D models of the homologous complexes. In spite of a low sequence similarity with their human counterparts, key structural features required for ligand–receptor and protein–heparin binding in humans are conserved in the fly and worm FGF–FGFR–heparin complexes. Analyses of the models show that tertiary interactions that are not conserved in sequence are maintained through novel interactions or complementary mutations in the fly and worm sequences. The overall charge distributions observed in the human FGF–FGFR–heparin complex are retained in the fly and worm models. The arginine residue at position 253 in the linker region between the Ig-like domains D2 and D3 in the wild type fly and worm sequences is particularly striking, as the Pro253Arg mutation in humans is responsible for Apert syndrome. This change may enhance the affinity of receptors for their FGF molecules as observed in Apert mutants.

New Zealand Maori family with the pro250arg fibroblast growth factor receptor 3 mutation associated with craniosynostosis

Background: A large New Zealand Maori family has non-syndromic coronal craniosynostosis, which is inherited as an autosomal dominant mutation with variable expression. The aim of the study is to determine whether the family has the pro250 arg mutation in the gene for fibroblast growth factor receptor 3 (FGFR3), a mutation found in patients with various types of craniosynostosis. Patients: Fourteen members of a New Zealand Maori family were evaluated, of whom five have coronal synostosis. A family pedigree tracing six generations was recorded. Methods: Blood samples were drawn for genomic DNA analysis from 14 family members. Polymerase chain reaction, restriction-enzyme digestion and DNA sequencing was performed to identify the pro250arg mutation in FGFR3. Results: Seven family members were heterozygous for the pro250arg mutation in FGFR3. The mutation showed autosomal dominance with reduced penetrance and variable expressivity. Conclusion: Our data and those of other investigators suggest that we should begin integrating molecular diagnosis with phenotypic diagnosis of craniosynostoses.

Syndrome of coronal craniosynostosis, Klippel-Feil anomaly, and sprengel shoulder with and without Pro250Arg mutation in the FGFR3 gene

A unique Pro250Arg point mutation in fibroblast growth factor receptor 3 (FGFR3) was initially reported by Bellus et al. [1996: Nat Genet 14:174-176] and the phenotype subsequently by Muenke et al. [1997: Am J Hum Genet 60:555-564], Reardon et al. [1997: J Med Genet 34:632-636], and Graham et al. [1998: Am J Med Genet 77:322-329]. These authors emphasized the pleiotropic nature of this form of coronal craniosynostosis, including brachydactyly with carpal and/or tarsal coalitions, with other anomalies at lower frequency. We report on a family with autosomal dominant coronal synostosis, segmentation and fusion anomalies of the vertebra and ribs, and Sprengel shoulder due to the Pro250Arg mutation. We also report a single case with an identical phenotype without the mutation.

A Pro250Arg substitution in mouse Fgfr1 causes increased expression of Cbfa1 and premature fusion of calvarial sutures.

Pfeiffer syndrome is a classic form of craniosynostosis that is caused by a proline-->arginine substitution at amino acid 252 (Pro252Arg) in fibroblast growth factor receptor 1 (FGFR1). Here we show that mice carrying a Pro250Arg mutation in Fgfr1, which is orthologous to the Pfeiffer syndrome mutation in humans, exhibit anterio-posteriorly shortened, laterally widened and vertically heightened neurocraniums. Analysis of the posterior and anterior frontal, sagittal and coronal sutures of early post-natal mutant mice revealed premature fusion. The sutures of mutant mice had accelerated osteoblast proliferation and increased expression of genes related to osteoblast differentiation, suggesting that bone formation at the sutures is locally increased in Pfeiffer syndrome. Of note, dramatically increased expression of core-binding transcription factor alpha subunit type 1 (Cbfa1) accompanied premature fusion, suggesting that Cbfa1 may be a downstream target of Fgf/Fgfr1 signals. This was confirmed in vitro, where we demonstrate that transfection with wild-type or mutant Fgfr1 induces Cbfa1 expression. The induced expression was also observed using Fgf ligands (Fgf2 and Fgf8). These studies provide direct genetic evidence that the Pro252Arg mutation in FGFR1 causes human Pfeiffer syndrome and uncovers a molecular mechanism in which Fgf/Fgfr1 signals regulate intramembraneous bone formation by modulating Cbfa1 expression.

A unique point mutation in the fibroblast growth factor receptor 3 gene (FGFR3) causes non‐syndromic craniosynostosis

A unique Pro250Arg mutation in fibroblast growth factor receptor 3 (FGFR3) was recently found in patients with non‐syndromic craniosynostosis. We studied 18 Taiwan Chinese patients with various types of craniosynostosis to evaluate if this mutation is also prevalent in the Chinese population. Genomic DNA was analysed by polymerase chain reaction based restriction analysis and direct sequencing to identify the Pro250Arg mutation in FGFR3. Five (28%) of 18 probands were heterozygous for the Pro250Arg mutation. Only those patients with coronal synostosis carried this mutation.Conclusion: Our findings suggest that all patients with coronal synostosis should be examined for this unique mutation.

A unique point mutation in the fibroblast growth factor receptor 3 gene (FGFR3) causes non-syndromic craniosynostosis.

A unique Pro250Arg mutation in fibroblast growth factor receptor 3 (FGFR3) was recently found in patients with non-syndromic craniosynostosis. We studied 18 Taiwan Chinese patients with various types of craniosynostosis to evaluate if this mutation is also prevalent in the Chinese population. Genomic DNA was analysed by polymerase chain reaction based restriction analysis and direct sequencing to identify the Pro250Arg mutation in FGFR3. Five (28%) of 18 probands were heterozygous for the Pro250Arg mutation. Only those patients with coronal synostosis carried this mutation. Our findings suggest that all patients with coronal synostosis should be examined for this unique mutation.