First missense mutation in the SOST gene causing sclerosteosis by loss of sclerostin function

Sclerosteosis is a rare bone dysplasia characterized by greatly increased bone mass, especially of the long bones and the skull. Patients are tall, show facial asymmetry and often have syndactyly. Clinical complications are due to entrapment of cranial nerves. The disease is thought to be due to loss‐of‐function mutations in the SOST gene. The SOST gene product, sclerostin, is secreted by osteocytes and transported to the bone surface where it inhibits osteoblastic bone formation by antagonizing Wnt signaling. In a small Turkish family with sclerosteosis, we identified a missense mutation (c.499T>C; p.Cys167Arg) in exon 2 of the SOST gene. This type of mutation has not been previously reported and using different functional approaches, we show that it has a devastating effect on the biological function of sclerostin. The affected cysteine is the last cysteine residue of the cystine‐knot motif and loss of this residue leads to retention of the mutant protein in the ER, possibly as a consequence of impaired folding. Together with a significant reduced ability to bind to LRP5 and inhibit Wnt signaling, the p.Cys167Arg mutation leads to a complete loss of function of sclerostin and thus to the characteristic sclerosteosis phenotype. © 2010 Wiley‐Liss, Inc.     

伴偏斜对下颌前突患者颞下颌关节应力分布的影响

目的探究伴偏斜对下颌前突患者颞下颌关节(temporomandibular joint,TMJ)应力分布的影响。方法在Mimics中建立4名下颌前突伴偏斜患者和4名下颌前突不伴偏斜患者的三维颌面部模型,在ABAQUS中赋予模型偏侧咬合(单侧磨牙咀嚼)的肌肉力与边界条件,分析偏侧咬合工况下患者TMJ的最大和最小主应力。结果偏侧咬合工况下,伴偏斜患者髁突的平均最大应力显著大于不伴偏斜患者(P<0.05),伴偏斜会使髁突处应力增加2~3倍,关节窝应力增加5~7倍,且伴偏斜患者中颞下颌关节紊乱综合征(temporomandibular disorder,TMD)患者同侧TMJ处的应力高于无TMD患者。结论伴偏斜会增大患者髁突和关节窝的应力,TMD会引起伴偏斜患者同侧TMJ的高应力。建议根据偏斜与否考虑下颌前突的治疗。     

Novel SOST gene mutation in a sclerosteosis patient from Morocco: A case report

Sclerosteosis (OMIM 269500) is a rare autosomal recessive condition characterized by increased bone density associated with syndactyly. It is linked to a genetic defect in the SOST gene coding for sclerostin. So far, seven different loss-of-function mutations in SOST have been reported in patients with sclerosteosis. Recently, two mutations in LRP4 gene underlying sclerosteosis were identified, reflecting the genetic heterogeneity of this disease.We report here a 30-years-old Moroccan man presented with typical clinical and radiological features of sclerosteosis who carries a novel homozygous mutation in the SOST gene, characterized as a nonsense mutation (c.79C > T; p.Gln271) in exon 1 of the SOST gene. This is to our knowledge the first case of sclerosteosis reported from Morocco and North Africa.     

Neural symmetry and functional asymmetry of the mandible

Even in the absence of malformation or skull base asymmetry, the mandible may be physiologically asymmetric and this remains a major challenge in the orthodontic treatment. The mandible is a bone formed by a primary subunit, i.e., the neural part, with different functional secondary subunits, so we suggest that in a normal mandible the asymmetry was caused by the secondary functional subunit and the neural part is nearly symmetric. Eighty-three dry human mandible samples were studied. The measurements of the size of the mandible (corpus, ramus, mandible notch, condylar process, the angle of the mandible) and the neural subunit (the mandibular canal and the position of the mental and mandibular foramina) were measured bilaterally. The left and right sides were compared according to the dental status: 60 dentate and 23 edentulous mandibles. The calculation of the symmetry was based on the paired Student t test, the absolute difference |R−L| and the relative absolute difference |R−L|/|R+L|×100. The mandibular canal and the position of the foramina were symmetric, except for the position of the mandibular foramen in relation to the mandible notch. The symmetry was not modified by the dental status. The total length of the mandible and the length of the ramus were greater on the left side independently from the dental status. The length of the corpus and the mandible angle were symmetric in each group. The mandible notch was always asymmetric and its height was greater in the dentate group. The condylar process was the most asymmetric structure in each group. The primary subunit of the mandible, surrounding the mandibular canal, is a symmetric component of the mandible and is not modified by the dental status. The angle of the mandible between the corpus and ramus is another symmetric parameter that is important for the facial architecture. The ramus and especially the mandibular notch as well as the condylar process are the most asymmetric subunits influenced by the functional matrices.     

Oral manifestations in patients and dogs with mucopolysaccharidosis Type VII

Mucopolysaccharidosis Type VII (MPS7, also called β‐glucuronidase deficiency or Sly syndrome; MIM 253220) is an extremely rare autosomal recessive lysosomal storage disease, caused by mutations in the GUSB gene. β‐glucuronidase (GUSB) is a lysosomal hydrolase involved in the stepwise degradation of glucuronic acid‐containing glycosaminoglycans (GAGs). Patients affected with MPS VII are not able to completely degrade glucuronic acid‐containing GAGs, including chondroitin 4‐sulfate, chondroitin 6‐sulfate, dermatan sulfate, and heparan sulfate. The accumulation of these GAGs in lysosomes of various tissues leads to cellular and organ dysfunctions. Characteristic features of MPS VII include short stature, macrocephaly, hirsutism, coarse facies, hearing loss, cloudy cornea, short neck, valvular cardiac defects, hepatosplenomegaly, and dysostosis multiplex. Oral manifestations in patients affected with MPS VII have never been reported. Oral manifestations observed in three patients consist of wide root canal spaces, taurodontism, hyperplastic dental follicles, malposition of unerupted permanent molars, and failure of tooth eruption with malformed roots. The unusual skeletal features of the patients include maxillary hypoplasia, hypoplastic midface, long mandibular length, mandibular prognathism, hypoplastic and aplastic mandibular condyles, absence of the dens of the second cervical vertebra, and erosion of the cortex of the lower border of mandibles. Dogs affected with MPS VII had anterior and posterior open bite, maxillary hypoplasia, premolar crowding, and mandibular prognathism. Unlike patients with MPS VII, the dogs had unremarkable mandibular condyles. This is the first report of oral manifestations in patients affected with MPS VII.     

ADAMTSL1 and mandibular prognathism

Mandibular prognathism is characterized by a prognathic or prominent mandible. The objective of this study was to find the gene responsible for mandibular prognathism. Whole exome sequencing analysis of a Thai family (family 1) identified the ADAMTSL1 c.176C>A variant as the potential defect. We cross-checked our exome data of 215 people for rare variants in ADAMTSL1 and found that the c.670C>G variant was associated with mandibular prognathism in families 2 and 4. Mutation analysis of ADAMTSL1 in 79 unrelated patients revealed the c.670C>G variant was also found in family 3. We hypothesize that mutations in ADAMTSL1 cause failure to cleave aggrecan in the condylar cartilage, and that leads to overgrowth of the mandible. Adamtsl1 is strongly expressed in the condensed mesenchymal cells of the mouse condyle, but not at the cartilage of the long bones. This explains why the patients with ADAMTSL1 mutations had abnormal mandibles but normal long bones. This is the first report that mutations in ADAMTSL1 are responsible for the pathogenesis of mandibular prognathism.     

Bilateral cleft lip and palate: A morphometric analysis of facial skeletal form using cone beam computed tomography

Bilateral cleft lip and palate (BCLP) is caused by a lack of merging of maxillary and nasal facial prominences during development and morphogenesis. BCLP is associated with congenital defects of the oronasal facial region that can impair ingestion, mastication, speech, and dentofacial development. Using cone beam computed tomography (CBCT) images, 7‐ to 18‐year old individuals born with BCLP (n = 15) and age‐ and sex‐matched controls (n = 15) were retrospectively assessed. Coordinate values of three‐dimensional facial skeletal anatomical landmarks (n = 32) were measured from each CBCT image. Data were evaluated using principal coordinates analysis (PCOORD) and Euclidean Distance Matrix Analysis (EDMA). PCOORD axes 1–3 explain approximately 45% of the morphological variation between samples, and specific patterns of morphological differences were associated with each axis. Approximately, 30% of facial skeletal measures significantly differ by confidence interval testing (α = 0.10) between samples. While significant form differences occur across the facial skeleton, strong patterns of differences are localized to the lateral and superioinferior aspects of the nasal aperture. In conclusion, the BCLP deformity significantly alters facial skeletal morphology of the midface and oronasal regions of the face, but morphological differences were also found in the upper facial skeleton and to a lesser extent, the lower facial skeleton. This pattern of strong differences in the oronasal region of the facial skeleton combined with differences across the rest of the facial complex underscores the idea that bones of the craniofacial skeleton are integrated. Clin. Anat. 28:584–592, 2015. © 2015 Wiley Periodicals, Inc.     

Evaluation of growth hormone axis and responsiveness to growth stimulation of short children with osteogenesis imperfecta

We present four individuals with Gerodermia Osteodysplastica in a Jewish family from Morocco confirming the autosomal recessive inheritance of the disorder. Three previously unreported findings are described: (a) enlarged funnel-shaped mandibular lingula; (b) extension of the mandibular premolar and molar roots below the inferior dental canal, and of the second molars into the lower border of mandibular cortical bone; and (c) hypercementosis of the maxillary incisors and mandibular molars surrounded by a radiolucent halo in several teeth. The facial deformity resulting from maxillary hypoplasia and mandibular prognathism was corrected by orthognathic surgery: Le Fort I maxillary osteotomy and vertical mandibular osteotomy. © 1993 Wiley-Liss, Inc.     

A 52‐kb deletion in the SOST‐MEOX1 intergenic region on 17q12‐q21 is associated with van Buchem disease in the Dutch population

Van Buchem disease is an autosomal recessive sclerosing bone dysplasia characterized by skeletal hyperostosis, overgrowth of the mandible, and a liability to entrapment of the seventh and eighth cranial nerves. The genetic determinant maps to chromosome 17q12‐q21. We refined the critical interval to the < 1‐Mb region between D17S2250 and D17S2253 in 15 affected individuals, all of whom shared a common disease haplotype. Furthermore, we report here the identification of a 52‐kb deletion located within the interval and encompassing D17S1789 that is 100% concordant with the disorder. Although the deletion itself does not appear to disrupt the coding region of any known or novel gene(s), the closest flanking genes are MEOX1 on the proximal side, and SOST on the distal side of the deletion. MEOX1 is known to be important for the development of the axial skeleton, whereas the SOST gene is the determinant of sclerosteosis, a disorder that shares many features with van Buchem disease, thus raising the possibility that van Buchem disease results from dysregulation of the expression of one or both of these genes. © 2002 Wiley‐Liss, Inc.     

Extending the phenotypes associated with TRIO gene variants in a cohort of 25 patients and review of the literature

The TRIO gene encodes a rho guanine exchange factor, the function of which is to exchange GDP to GTP, and hence to activate Rho GTPases, and has been described to impact neurodevelopment. Specific genotype-to-phenotype correlations have been established previously describing striking differentiating features seen in variants located in specific domains of the TRIO gene that are associated with opposite effects on RAC1 activity. Currently, 32 cases with a TRIO gene alteration have been published in the medical literature. Here, we report an additional 25, previously unreported individuals who possess heterozygous TRIO variants and we review the literature. In addition, functional studies were performed on the c.4394A > G (N1465S) and c.6244-2A > G TRIO variants to provide evidence for their pathogenicity. Variants reported by the current study include missense variants, truncating nonsense variants, and an intragenic deletion. Clinical features were previously described and included developmental delay, learning difficulties, microcephaly, macrocephaly, seizures, behavioral issues (aggression, stereotypies), skeletal problems including short, tapering fingers and scoliosis, dental problems (overcrowding/delayed eruption), and variable facial features. Here, we report clinical features that have not been described previously, including specific structural brain malformations such as abnormalities of the corpus callosum and ventriculomegaly, additional psychological and dental issues along with a more recognizable facial gestalt linked to the specific domains of the TRIO gene and the effect of the variant upon the function of the encoded protein. This current study further strengthens the genotype-to-phenotype correlation that was previously established and extends the range of phenotypes to include structural brain abnormalities, additional skeletal, dental, and psychiatric issues.     

Nasal Septal Deviation and Facial Skeletal Asymmetries

During ontogeny, the nasal septum exerts a morphogenetic influence on the surrounding facial skeleton. While the influence of the septum is well established in long snouted animal models, its role in human facial growth is less clear. If the septum is a facial growth center in humans, we would predict that deviated septal growth would be associated with facial skeletal asymmetries. Using computed tomographic (CT) scans of n = 55 adult subjects, the purpose of this study was to test whether there is a correlation between septal deviation and facial asymmetries using three‐dimensional (3D) geometric morphometric techniques. We calculated deviation as a percentage of septal volume relative to the volume of a modeled non‐deviated septum. We then recorded skeletal landmarks representing the nasal, palatal, and lateral facial regions. Landmark data were superimposed using Procrustes analysis. First, we examined the correlation between nasal septal deviation and the overall magnitude of asymmetry. Next, we assessed whether there was a relationship between nasal septal deviation and more localized aspects of asymmetry using multivariate regression analysis. Our results indicate that while there was no correlation between septal deviation and the overall magnitude of asymmetry, septal deviation was associated with asymmetry primarily in the nasal floor and the palatal region. Septal deviation was unassociated with asymmetries in the lateral facial skeleton. Though we did not test the causal relationship between nasal septal deviation and facial asymmetry, our results suggest that the nasal septum may have an influence on patterns of adult facial form. Anat Rec, 299:295–306, 2016. © 2016 Wiley Periodicals, Inc.     

Microcephalia with mandibular and dental dysplasia in adult Zmpste24‐deficient mice

ZMPSTE24 (also called FACE‐1) is a zinc‐metalloprotease involved in the post‐translational processing of prelamin A to mature lamin A, a major component of the nuclear envelope. Mutations in the ZMPSTE24 gene or in that encoding its substrate prelamin A (LMNA) result in a series of human inherited diseases known collectively as laminopathies and showing regional or systemic manifestations (i.e. the Hutchinson–Gilford progeria syndrome). Typically, patients suffering some laminopathies show craniofacial or mandible anomalies, aberrant dentition or facial features characteristic of aged persons. To analyse whether Zmpste24^?/– mice reproduce the cranial phenotype observed in humans due to mutations in ZMPSTE24 or LMNA, we conducted a craniometric study based on micro‐computer tomography (µCT) images. Furthermore, using simple radiology, µCT, µCT‐densitometry and scanning electron microscopy, we analysed the mandible and the teeth from Zmpste24^?/– mice. Finally, the structure of the lower incisor was investigated using an H&E technique. The results demonstrate that Zmpste24^?/– mice are microcephalic and show mandibular and dental dysplasia affecting only the mandible teeth. In all cases, the lower incisor of mice lacking Zmpste24 was smaller than in control animals, showed cylindrical morphology and a transverse fissure at the incisal edge, and the pulpal cavity was severely reduced. Structurally, the dental layers were normally arranged but cellular layers were disorganized. The inferior molars showed a reduced cusp size. Taken together, these data strongly suggest that Zmpste24^?/– mice represent a good model to analyse the craniofacial and teeth malformations characteristic of lamin‐related pathologies, and might contribute to a better understanding of the molecular events underlying these diseases.     

Power and challenges of using zebrafish as a model for skeletal tissue imaging

Abstract

The zebrafish (Danio rerio) is now a widely used model organism in biomedical research. The species is also increasingly used for studying skeletal development and regeneration and for understanding human skeletal diseases. The small size of this model organism is an advantage and an extreme challenge for visualizing and diagnosing the animals’ skeleton. This applies especially to early stages of skeletal development. Similar challenges arise for the analysis of the skeleton of other small fish species, such as medaka (Oryzias latipes). High quality histological preparations and knowledge about the special quality of the zebrafish skeleton remain prerequisites for a correct analysis. In addition, new methods for fast and high-resolution 2D and 3D skeletal tissue screening are required for a maximal understanding of skeletal development. We, in this study, review advantages and limitations of adapting current visualization techniques for zebrafish skeletal research. We discuss the methods for in toto visualization, such as X-raying, micro-CT, Alizarin red staining and optical projection tomography. Techniques for in vivo imaging, such as second harmonic generation microscopy and two-photon excitation fluorescence, are also discussed. Finally, we explore the possibilities of light-sheet microscopy for the analysis of the zebrafish skeleton.     

Facial soft tissue changes after maxillary impaction and mandibular advancement in high angle class II cases

The aim of this study was to determine the vertical and anteroposterior alterations in the soft, the dental and the skeletal tissues associated with the facial profile after Le Fort I maxillary impaction in conjunction with sagittal split osteotomy for mandibular advancement performed in patients with a high angle Class II skeletal deformity.The study population consists of 21 patients (11 females and 10 males, mean age 24.5±1.6 years) who underwent Le Fort I maxillary impaction in conjunction with sagittal split osteotomy for mandibular advancement. Lateral cephalograms were obtained prior to the surgery and 1.3±0.2 years postoperatively. Wilcoxon test was performed to compare the pre- and postsurgical cephalometric measurements. Pearson correlation test was carried out to determine the relative changes in skeletal, dental and the facial soft tissues.The insignificant decrease in the nasolabial angle was correlated with the significant decrease in the vertical position of the nose due to the nasal protraction noticed after bimaxillary surgery. The retraction of both the upper lip and the upper incisors was correlated with the insignificant decrease in the columella-lobular angle. The insignificant decrease in both the vertical height of the mandibular B point and the lower incisors was correlated with the insignificant decrease in vertical height of the soft tissue pogonion, attributable to the resulting superior movement of the soft tissues of the chin and the counter clockwise rotation of the mandible after maxillary impaction and bilateral sagittal split osteotomy, respectively.Le Fort I maxillary impaction in conjunction with mandibular sagittal split osteotomy for mandibular advancement significantly affected the vertical and anteroposterior positions of the maxilla and the mandible, respectively. When performed in combination, these surgical techniques may efficiently alter the position of upper incisor and the nasal position in both vertical and anteroposterior directions. Bimaxillary orthognathic surgery seems to be an efficient method for obtaining satisfactory results in the appearance of the soft, the dental and the skeletal tissues associated with the facial profile in patients with high angle Class II skeletal deformity.     

The facial skeleton of the chimpanzee-human last common ancestor

This review uses the current morphological evidence to evaluate the facial morphology of the hypothetical last common ancestor (LCA) of the chimpanzee/bonobo (panin) and human (hominin) lineages. Some of the problems involved in reconstructing ancestral morphologies so close to the formation of a lineage are discussed. These include the prevalence of homoplasy and poor phylogenetic resolution due to a lack of defining derived features. Consequently the list of hypothetical features expected in the face of the LCA is very limited beyond its hypothesized similarity to extant Pan. It is not possible to determine with any confidence whether the facial morphology of any of the current candidate LCA taxa (Ardipithecus kadabba, Ardipithecus ramidus, Orrorin tugenensis and Sahelanthropus tchadensis) is representative of the LCA, or a stem hominin, or a stem panin or, in some cases, a hominid predating the emergence of the hominin lineage. The major evolutionary trends in the hominin lineage subsequent to the LCA are discussed in relation to the dental arcade and dentition, subnasal morphology and the size, position and prognathism of the facial skeleton.     

On the genetics of mandibular prognathism: analysis of large European noble families.

Mandibular prognathism is assumed to be a polygenic trait in the vast majority of cases. In a few families, this phenotype and perhaps a syndrome with a broader spectrum of facial anomalies seems to be determined by a single dominant gene of very low frequency (McKusick No *176700). The phenotype is known to have occurred independently in several European noble families. We constructed a pedigree comprising 13 of these families with 409 members in 23 generations in which mandibular prognathism has been segregating. Obviously, the presumed dominant gene is not fully penetrant in the heterozygous state. Pedigree analysis using the Elston-Stewart algorithm yields a maximum likelihood estimate (MLE) of p = 0.955 (SE 0.038) of the penetrance parameter.     

YPEL1 overexpression in early avian craniofacial mesenchyme causes mandibular dysmorphogenesis by up‐regulating apoptosis

Background: The YPEL (Yippee‐like) gene family comprises five highly conserved members (YPEL1‐5), but their biological function remains largely unknown. Early studies of YPEL1 function suggested that it plays a role in the development of structures derived from the pharyngeal arches. Human YPEL1 localises to distal chromosome 22q11.2 and copy number changes at this locus lead to diverse phenotypes that include facial dysmorphism, facial asymmetry, and palatal anomalies comprising the distal 22q11.2 deletion/duplication syndromes (OMIM 611867). We therefore investigated the role of chick YPEL1 in craniofacial development using ex vivo and in vivo approaches in the avian model. Results: We found that retroviral‐mediated in vivo overexpression of YPEL1 causes abnormal mandibular morphogenesis associated with increased apoptosis and involvement of the BMP/MSX pathway. Conclusions: Our results suggest that YPEL1 expression is regulated by bone morphogenetic protein signaling and suggest a role for YPEL1 in the pathogenesis of the craniofacial abnormalities observed in humans with distal chromosome 22q11.2 deletions or duplications. Developmental Dynamics 244:1022–1030, 2015. © 2015 Wiley Periodicals, Inc.     

Major gene and multifactorial inheritance of mandibular prognathism

Mandibular prognathism typically shows familial aggregation. Various genetic models have been described and it is assumed to be a multifactorial and polygenic trait, with a threshold for expression. Our goal was to examine specific genetic models of the familial transmission of this trait. The study sample comprised of 2,562 individuals from 55 families. Complete family histories for each proband were ascertained and the affection status of relatives were confirmed by lateral cephalograms, photographs, and dental models. Pedigrees were drawn using PELICAN and complex segregation analysis was performed using POINTER. Parts of some pedigrees were excluded to create one founder pedigrees, so the total N was 2,050. Analysis showed more affected females than males (P = 0.030). The majority of the pedigrees suggest autosomal dominant inheritance. Incomplete penetrance was demonstrated by the ratio of affected/unaffected parents and siblings. The heritability of mandibular prognathism was estimated to be 0.316. We conclude that there is a major gene that influences the expression of mandibular prognathism with clear signs of Mendelian inheritance and a multifactorial component.