A novel mutation in EFNB1, probably with a dominant negative effect, underlying craniofrontonasal syndrome

Aberrant cell segregation in the craniofacial primordium and the emergence of facial dysmorphology in craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS) is a rare X-linked disorder characterized by craniofacial, skeletal, and neurological anomalies and is caused by mutations in EFNB1. Heterozygous females are more severely affected by CFNS than hemizygous males, a phenomenon called cellular interference that results from EPHRIN-B1 mosaicism. In Efnb1 heterozygous mice, mosaicism for EPHRIN-B1 results in cell sorting and more severe phenotypes than Efnb1 hemizygous males, but how craniofacial dysmorphology arises from cell segregation is unknown and CFNS etiology therefore remains poorly understood. Here, we couple geometric morphometric techniques with temporal and spatial interrogation of embryonic cell segregation in mouse mutant models to elucidate mechanisms underlying CFNS pathogenesis. By generating EPHRIN-B1 mosaicism at different developmental timepoints and in specific cell populations, we find that EPHRIN-B1 regulates cell segregation independently in early neural development and later in craniofacial development, correlating with the emergence of quantitative differences in face shape. Whereas specific craniofacial shape changes are qualitatively similar in Efnb1 heterozygous and hemizygous mutant embryos, heterozygous embryos are quantitatively more severely affected, indicating that Efnb1 mosaicism exacerbates loss of function phenotypes rather than having a neomorphic effect. Notably, neural tissue-specific disruption of Efnb1 does not appear to contribute to CFNS craniofacial dysmorphology, but its disruption within neural crest cell-derived mesenchyme results in phenotypes very similar to widespread loss. EPHRIN-B1 can bind and signal with EPHB1, EPHB2, and EPHB3 receptor tyrosine kinases, but the signaling partner(s) relevant to CFNS are unknown. Geometric morphometric analysis of an allelic series of Ephb1; Ephb2; Ephb3 mutant embryos indicates that EPHB2 and EPHB3 are key receptors mediating Efnb1 hemizygous-like phenotypes, but the complete loss of EPHB1-3 does not fully recapitulate the severity of CFNS-like Efnb1 heterozygosity. Finally, by generating Efnb1+/Δ; Ephb1; Ephb2; Ephb3 quadruple knockout mice, we determine how modulating cumulative receptor activity influences cell segregation in craniofacial development and find that while EPHB2 and EPHB3 play an important role in craniofacial cell segregation, EPHB1 is more important for cell segregation in the brain; surprisingly, complete loss of EPHB1-EPHB3 does not completely abrogate cell segregation. Together, these data advance our understanding of the etiology and signaling interactions underlying CFNS dysmorphology.

Trio-Based Whole-Exome Sequencing Identifies a De novo EFNB1 Mutation as a Genetic Cause in Female Infant With Brain Anomaly and Developmental Delay

Background: Craniofrontonasal syndrome is a rare, X-linked disorder in which heterozygous females ironically reported the majority of patients and is caused by in the EFNB1 gene located at chromosome Xq13.1. Unlike previous reports, we present a female infant with a de novo EFNB1 missense mutation that was demonstrated in clinical diagnosis as global developmental delay (GDD) and brain anomaly without frontonasal dysplasia or other malformation. Case Presentation: This study reports the genetic analysis of a 4-month-old female infant presenting brain anomaly and GDD. She was the only child of unrelated parents. Early developmental was characterized by delays in fine motor, achieving gross motor, language, and social-cognitive milestones. She could not control her head or hold objects until 4 months of age. Brain magnetic resonance imaging revealed schizencephaly and dysgenesis of corpus callosum. Trio-based whole-exome sequencing revealed a heterozygous c.943C>T (p.Pro315Ser) in the EFNB1. Sanger sequencing confirmed this heterozygous alteration occurring in a dominant de novo manner, as a consequence of phenotypic and genotypic wild type in both parents. Conclusion: EFNB1 mutation is considered for a child with schizencephaly, and further study focusing on phenotyping is required to understand the possible contribution of environmental impact and genetic modifier in the expression of EFNB1.

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.

Craniofrontonasal Syndrome Caused by Introduction of a Novel uATG in the 5'UTR of EFNB1

Craniofrontonasal syndrome (CFNS) is an X-linked disorder caused by EFNB1 mutations in which females are more severely affected than males. Severe male phenotypes are associated with mosaicism, supporting cellular interference for sex bias in this disease. Although many variants have been found in the coding region of EFNB1, only 2 pathogenic variants have been identified in the same nucleotide in 5'UTR, disrupting the stop codon of an upstream open reading frame (uORF). uORFs are known to be part of a wide range of post-transcriptional regulation processes, and just recently, their association with human diseases has come to light. In the present study, we analyzed EFNB1 in a female patient with typical features of CFNS. We identified a variant, located at c.-411, creating a new upstream ATG (uATG) in the 5'UTR of EFNB1, which is predicted to alter an existing uORF. Dual-luciferase reporter assays showed significant reduction in protein translation, but no difference in the mRNA levels. Our study demonstrates, for the first time, the regulatory impact of uATG formation on EFNB1 levels and suggests that this should be the target region in molecular diagnosis of CFNS cases without pathogenic variants in the coding and splice sites regions of EFNB1.

Value of Osteoblast-Derived Exosomes in Bone Diseases

PURPOSE

The authors' purpose is to reveal the value of osteoblast-derived exosomes in bone diseases.

METHODS

Microvesicles from supernatants of mouse Mc3t3 were isolated by ultracentrifugation and then the authors presented the protein profile by proteomics analysis.

RESULTS

The authors detected a total number of 1536 proteins by mass spectrometry and found 172 proteins overlap with bone database. The Ingenuity Pathway Analysis shows network of "Skeletal and Muscular System Development and Function, Developmental Disorder, Hereditary Disorder" and pathway about osteogenesis. EFNB1 and transforming growth factor beta receptor 3 in the network, LRP6, bone morphogenetic protein receptor type-1, and SMURF1 in the pathway seemed to be valuable in the exosome research of related bone disease.

CONCLUSIONS

The authors' study unveiled the content of osteoblast-derived exosome and discussed valuable protein in it which might provide novel prospective in bone diseases research.

A Family with Craniofrontonasal Syndrome: The First Report of Familial Cases of Craniofrontonasal Syndrome with Bilateral Cleft Lip and Palate

Craniofrontonasal syndrome (CFNS) is a very rare genetic disorder, the common physical malformations of which include coronal synostosis, widely spaced eyes, clefting of the nasal tip, and various skeletal anomalies. Mutations of EFNB1, which encodes a member of the ephrin family of transmembrane ligands for Eph receptor tyrosine kinases, is the cause of CFNS. Although familial CFNS cases have been reported, no studies in the literature describe familial cases of CFNS expressing bilateral cleft lip and palate. Here, we describe a Japanese family with three cases of CFNS expressing bilateral cleft lip and palate.

Genome-Wide Association Studies for Comb Traits in Chickens

The comb, as a secondary sexual character, is an important trait in chicken. Indicators of comb length (CL), comb height (CH), and comb weight (CW) are often selected in production. DNA-based marker-assisted selection could help chicken breeders to accelerate genetic improvement for comb or related economic characters by early selection. Although a number of quantitative trait loci (QTL) and candidate genes have been identified with advances in molecular genetics, candidate genes underlying comb traits are limited. The aim of the study was to use genome-wide association (GWA) studies by 600 K Affymetrix chicken SNP arrays to detect genes that are related to comb, using an F2 resource population. For all comb characters, comb exhibited high SNP-based heritability estimates (0.61-0.69). Chromosome 1 explained 20.80% genetic variance, while chromosome 4 explained 6.89%. Independent univariate genome-wide screens for each character identified 127, 197, and 268 novel significant SNPs with CL, CH, and CW, respectively. Three candidate genes, VPS36, AR, and WNT11B, were determined to have a plausible function in all comb characters. These genes are important to the initiation of follicle development, gonadal growth, and dermal development, respectively. The current study provides the first GWA analysis for comb traits. Identification of the genetic basis as well as promising candidate genes will help us understand the underlying genetic architecture of comb development and has practical significance in breeding programs for the selection of comb as an index for sexual maturity or reproduction.

Use of targeted next-generation sequencing for molecular diagnosis of craniosynostosis: Identification of a novel de novo mutation of EFNB1

Craniofrontonasal syndrome (CFNS; MIM#304110) is characterized by asymmetric facial features with hypertelorism and a broad bifid nose due to synostosis of the coronal suture. CFNS shows a unique X-linked inheritance pattern (most affected patients are female and obligate male carriers exhibit a mild manifestation or no typical features at all) associated with the ephrin-B1 gene (EFNB1) located in the Xq13.1 region. In this study, we performed targeted, massively parallel sequencing using a next-generation sequencer, and identified a novel EFNB1 mutation, c.270_271delCA, in a Japanese female patient with craniosynostosis. Because subsequent Sanger sequencing identified no mutation in either parent, this mutation was determined to be de novo in origin. After obtaining molecular diagnosis, a retrospective clinical evaluation confirmed the clinical diagnosis of CFNS in this patient. Comprehensive molecular diagnosis using a next-generation sequencer would be beneficial for early diagnosis of the patients with undiagnosed craniosynostosis.

Report of a family with craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS, OMIM 304110) paradoxically presents a severe phenotype in heterozygous females and a mild or a normal phenotype in hemizygous males. Hypertelorism is seen in almost all of the female CFNS patients; craniosynostosis, facial asymmetry, and bifid nose are the other major clinical features. Most of the males are mildly affected, frequently only with hypertelorism. Here, we report a family with a G151S mutation in the EFNB1 gene. The mutation was identified in two severely affected sisters and paradoxically in their clinically unaffected father. The father on whom we report is the first male patient genetically proved to carry a CFNS-causing mutation and not presenting any signs nor symptoms of CFNS.

Isolated Sagittal Synostosis in a Boy with Craniofrontonasal Dysplasia and a Novel EFNB1 Mutation

Craniofrontonasal syndrome (CFNS) is a rare X-linked disorder that shows greater severity in females and is largely attributed to mutations in EFNB1. A 7-year-old boy presented with hypertelorism, broad nasal root, midfacial hypoplasia, mandibular prognathia, ptosis, and scaphocephaly was clinically diagnosed with CFNS. Three-dimensional computed tomographic scans confirmed the isolated sagittal synostosis. His mother also showed clinical features of CFNS, but less severe. Genetic tests uncovered a novel C to T mutation at nucleotide 466 (c.466C>T) in exon 1 of EFNB1 for both. To the best of our knowledge, this is the only reported incident of CFNS in a male child exhibiting isolated sagittal synostosis.

Phenotypes of craniofrontonasal syndrome in patients with a pathogenic mutation in EFNB1

Craniofrontonasal syndrome (CFNS) is an X-linked developmental malformation, caused by mutations in the EFNB1 gene, which have only been described since 2004. A genotype-phenotype correlation seems not to be present. As it is of major importance to adequately counsel patients with EFNB1 mutations and their parents, and to improve diagnosis of new patients, more information about the phenotypic features is needed. This study included 23 patients (2 male, 21 female) with confirmed EFNB1 mutations. All patients underwent a thorough physical examination and photographs were taken. If available, radiological images were also consulted. Hypertelorism, longitudinal ridging and/or splitting of nails, a (mild) webbed neck and a clinodactyly of one or more toes were the only consistent features observed in all patients. Frequently observed phenotypic features were bifid tip of the nose (91%), columellar indentation (91%) and low implantation of breasts (90%). In comparison with anthropometric data of facial proportions, patients with CFNS had a significantly different face in multiple respects. An overview of all phenotypic features is shown. Patients with EFNB1 mutations have a clear phenotype. This study will facilitate genetic counseling of parents and patients, and contribute to the diagnostic and screening process of patients with suspected CFNS.

The impact of CFNS-causing EFNB1 mutations on ephrin-B1 function

Background

Mutations of EFNB1 cause the X-linked malformation syndrome craniofrontonasal syndrome (CFNS). CFNS is characterized by an unusual phenotypic pattern of inheritance, because it affects heterozygous females more severely than hemizygous males. This sex-dependent inheritance has been explained by random X-inactivation in heterozygous females and the consequences of cellular interference of wild type and mutant EFNB1-expressing cell populations. EFNB1 encodes the transmembrane protein ephrin-B1, that forms bi-directional signalling complexes with Eph receptor tyrosine kinases expressed on complementary cells. Here, we studied the effects of patient-derived EFNB1 mutations predicted to give rise to truncated ephrin-B1 protein or to disturb Eph/ephrin-B1 reverse ephrin-B1 signalling. Five mutations are investigated in this work: nonsense mutation c.196C > T/p.R66X, frameshift mutation c.614_615delCT, splice-site mutation c.406 + 2T > C and two missense mutations p.P54L and p.T111I. Both missense mutations are located in the extracellular ephrin domain involved in Eph-ephrin-B1 recognition and higher order complex formation.

Methods

Nonsense mutation c.196C > T/p.R66X, frameshift mutation c.614_615delCT and splice-site mutation c.406+2T > C were detected in the primary patient fibroblasts by direct sequencing of the DNA and were further analysed by RT-PCR and Western blot analyses.

The impact of missense mutations p.P54L and p.T111I on cell behaviour and reverse ephrin-B1 cell signalling was analysed in a cell culture model using NIH 3T3 fibroblasts. These cells were transfected with the constructs generated by in vitro site-directed mutagenesis. Investigation of missense mutations was performed using the Western blot analysis and time-lapse microscopy.

Results and Discussion

Nonsense mutation c.196C > T/p.R66X and frameshift mutation c.614_615delCT escape nonsense-mediated RNA decay (NMD), splice-site mutation c.406+2T > C results in either retention of intron 2 or activation of a cryptic splice site in exon 2. However, c.614_615delCT and c.406+2T > C mutations were found to be not compatible with production of a soluble ephrin-B1 protein. Protein expression of the p.R66X mutation was predicted unlikely but has not been investigated.

Ectopic expression of p.P54L ephrin-B1 resists Eph-receptor mediated cell cluster formation in tissue culture and intracellular ephrin-B1 Tyr324 and Tyr329 phosphorylation. Cells expressing p.T111I protein show similar responses as wild type expressing cells, however, phosphorylation of Tyr324 and Tyr329 is reduced.

Conclusions

Pathogenic mechanisms in CFNS manifestation include impaired ephrin-B1 signalling combined with cellular interference.

Osteoclasts have multiple roles in bone in addition to bone resorption

Osteoclasts are the cells that degrade bone to initiate normal bone remodeling and mediate bone loss in pathologic conditions by increasing their resorptive activity. They are derived from precursors in the myeloid/ monocyte lineage that circulate in the blood after their formation in the bone marrow. These osteoclast precursors (OCPs) are attracted to sites on bone surfaces destined for resorption and fuse with one another to form the multinucleated cells that resorb calcified matrixes under the influence of osteoblastic cells in bone marrow. Recent studies have identified functions for OCPs and osteoclasts in and around bone other than bone resorption. For example, they regulate the differentiation of osteoblast precursors and the movement of hematopoietic stem cells from the bone marrow to the bloodstream; they participate in immune responses, and secrete cytokines that can affect their own functions and those of other cells in inflammatory and neoplastic processes affecting bone. Here, we review these findings, which define new roles for osteoclasts and OCPs in the growing field of osteoimmunology and in common pathologic conditions in which bone resorption is increased.

A subset of signal transduction pathways is required for hippocampal growth cone collapse induced by ephrin-A5

The Eph family tyrosine kinase receptors and their ligands, ephrins, play key roles in a wide variety of physiological and pathological processes including tissue patterning, angiogenesis, bone development, carcinogenesis, axon guidance, and neural plasticity. However, the signaling mechanisms underlying these diverse functions of Eph receptors have not been well understood. In this study, effects of Eph receptor activation on several important signal transduction pathways are examined. In addition, the roles of these pathways in ephrin-A5-induced growth cone collapse were assessed with a combination of biochemical analyses, pharmacological inhibition, and overexpression of dominant-negative and constitutively active mutants. These analyses showed that ephrin-A5 inhibits Erk activity but activates c-Jun N-terminal kinase. However, regulation of these two pathways is not required for ephrin-A5-induced growth cone collapse in hippocampal neurons. Artificial Erk activation by expression of constitutively active Mek1 and B-Raf failed to block ephrin-A5 effects on growth cones, and inhibitors of the Erk pathway also failed to inhibit collapse by ephrin-A5. Inhibition of JNK had no effects on ephrin-A5-induced growth cone collapse either. In addition, inhibitors to PKA and PI3-K showed no effects on ephrin-A5-induced growth cone collapse. However, pharmacological blockade of phosphotyrosine phosphatase activity, the Src family kinases, cGMP-dependent protein kinase, and myosin light chain kinase significantly inhibited ephrin-A5-induced growth cone collapse. These observations indicate that only a subset of signal transduction pathways is required for ephrin-A5-induced growth cone collapse.

Cranial suture biology and dental development: genetic and clinical perspectives

Premature fusion of the calvarial bones at the sutures, or craniosynostosis (CS), is a relatively common birth defect (1:2000-3000) frequently associated with limb deformity. Patients with CS may present oral defects, such as cleft soft palate, hypodontia, hyperdontia, and delayed tooth eruption, but also unusual associations of major dental anomalies such as taurodontism, microdontia, multiple dens invaginatus, and dentin dysplasia. The list of genes that are involved in CS includes those coding for the different fibroblast growth factor receptors and a ligand of ephrin receptors, but also genes encoding transcription factors, such as MSX2 and TWIST. Most of these genes are equally involved in odontogenesis, providing a pausible explanation for clinical associations of CS with dental agenesis or tooth malformations. On the basis of the present knowledge on genes and transcription factors that are involved in craniofacial morphogenesis, and from dental clinics of CS syndromes, the molecular mechanisms that control suture formation and suture closure are expected to play key roles in patterning events and development of teeth. The purpose of this article is to review and merge the recent advances in the field of suture research at the genetic and cellular levels with those of tooth development, and to apply them to the dental clinics of CS syndromes. These new perspectives and future challenges in the field of both dental clinics and molecular genetics, more in particular the identification of possible candidate genes involved in both CS and dental defects, are discussed.

Contiguous gene deletions involving EFNB1, OPHN1, PJA1 and EDA in patients with craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS [MIM 304110]) is an X-linked malformation syndrome characterized by craniofrontonasal dysplasia and extracranial manifestations in heterozygous females. In the majority of patients CFNS is caused by mutations in the EFNB1 gene (MIM 300035). We identified three girls with classical CFNS and mild developmental delay harboring de novo deletions of the EFNB1 gene. Applying haplotype analysis, Southern blot hybridization and array-comparative genomic hybridization, deletion of EFNB1 was found to be part of contiguous gene deletions in the patients. In one patient the deletion interval includes the genes for oligophrenin-1 (OPHN1 [MIM 300127]) and praja 1 (PJA1 [MIM 300420]). In the second patient the deletion includes OPHN1, PJA1 and the gene for ectodysplasin A (EDA [MIM 300451]). In the third patient EFNB1 gene deletion may include deletion of regulatory regions 5' of OPHN1. Previously, the OPHN1 gene has been shown to be responsible for recessive X-linked mental retardation. Although it is too early to predict the future cognitive performance of the two infant patients with contiguous gene deletions of OPHN1-EFNB1-PJA1, mild learning disabilities have been recognized in the older, third patient. It is important for genetic counseling to be aware that their male offspring may not only be carriers of CFNS but may also be affected by mental retardation and anhidrotic ectodermal dysplasia.

EFNB1 mutation at the ephrin ligand-receptor dimerization interface in a patient with craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS) is characterized by craniosynostosis, hypertelorism, a broad nasal tip and occasionally cleft lip and palate, and is caused by a mutation in the ephrin-B1 gene (EFNB1). The study of naturally occurring human EFNB1 mutations offers a unique opportunity to better define the critical portion within the ephrin domain that is essential for the function of EFNB1 protein in craniofacial development. Here, we report a CFNS patient with a novel EFNB1 missense mutation present at the interface between EFNB1 and its receptor proteins. The patient's facial features included hypertelorism, a broad nasal tip, brachycephaly, frontal bossing, facial asymmetry and esotropia. In addition, she had pectus carinatum, grooved nails on her thumb, an abnormal palmar crease pattern and a broad first toe. Her development was appropriate for her age. Direct sequencing of polymerase chain reaction products using an autosequencer revealed a heterozygous missense mutation, Ser118Ile. Ser118 is located in the G-H loop of the extracellular ephrin domain and is highly evolutionarily conserved among rodents, avians and fish. The mutation occurred de novo and was not present in 100 normal Japanese control subjects. Substitutions of the adjacent amino acid residue, Pro119, have been previously reported in three CFNS patients. Since the structure of EFNB1 is not yet available, the spatial locality of Ser118 was characterized using the protein structure of EFNB2. We deduced that Ser118 in EFNB1 resides at the major dimerization interface with Eph receptors and inferred that the Ser118Ile mutation may impede the protrusion of the G-H loop, thereby disturbing Eph-Ephrin signal transduction.