Showing papers in "Journal of Craniofacial Genetics and Developmental Biology in 1999"

Cranial suture obliteration is induced by removal of transforming growth factor (TGF)-beta 3 activity and prevented by removal of TGF-beta 2 activity from fetal rat calvaria in vitro.

Abstract: Cranial suture morphogenesis requires soluble, heparin-binding factors secreted by the dura mater to resist premature osseous obliteration. Elevated levels of transforming growth factor (TGF)-beta 1, TGF-beta 2, and TGF-beta 3 have previously been noted in cranial sutures undergoing normal and premature sutural obliteration. To examine the role of TGF-beta s in regulating cranial suture morphogenesis, an established in vitro, serum-free, calvarial culture system was used. In this system, fetal rat coronal sutures undergo apparently normal suture morphogenesis in the presence of dura mater, but undergo osseous obliteration in the absence of dura mater. Neutralizing polyclonal antibodies to TGF-beta 1, TGF-beta 2, or TGF-beta 3 were added to cultures of fetal day 19 rat calvaria, which were harvested at 3, 4, or 5 days, processed for histology, sectioned, and examined. Coronal sutures from calvaria cultured in the presence of dura mater resisted obliteration, either alone or in the presence of TGF-beta 1 or TGF-beta 2 neutralizing antibodies. However, sutures from calvaria cultured in the presence of TGF-beta 3 neutralizing antibodies became obliterated. Conversely, sutures from calvaria cultured in the absence of dura mater became obliterated by bone, either alone or in the presence of neutralizing antibodies to TGF-beta 1 or TGF-beta 3. However, those sutures cultured in the presence of neutralizing antibodies to TGF-beta 2 were rescued from osseous obliteration.

Morphometry of the normal human ear: a cross-sectional study from adolescence to mid-adulthood.

Abstract: The objective of this study was to supply information about: (1) normal gender-based dimensions of ears (linear distances and ratios, area); (2) left right symmetry; and (3) growth changes between adolescence and mid-adulthood. The three-dimensional co-ordinates of several soft-tissue landmarks on the ears and face were obtained by an electromagnetic digitizer in 40 male and 33 female adolescents aged 12-15 years. 73 young female and 89 young male adults aged 19-30 years, and 41 male and 38 female adults aged 31-56 years. From the landmarks, paired car width and length were calculated and averaged for age and gender, as well as the relevant ratios, ear areas and angles relative to the facial midline, and indices of left right symmetry. Comparisons were performed by factorial analysis of variance. All ear dimensions were significantly larger in men than in women (P < 0.005). A significant effect of age was found (P < 0.005), with larger values in older individuals. On average, the three-dimensional position of ears was symmetric, with symmetry coefficients ranging between 94 and 96%. Data collected in the present investigation could serve as a database for the quantitative description of human ear morphology during normal adolescent and adult growth.

Cephalometric study of the Apert syndrome in adolescence and adulthood.

Abstract: This paper reports a cephalometric analysis of the craniofacial morphology in adolescents and adults with Apert syndrome. The sample comprised 26 patients with Apert syndrome (15 males and 11 females). The control group consisted of 153 adults (102 males and 51 females). Both lateral and frontal cephalograms were studied. The data were presented as mean plots of the craniofacial region together with data on some of the most significant findings. Marked differences were found in nearly all craniofacial regions except the mandible. The calvaria was increased in height and width but length was decreased. The cranial base showed marked protrusion of the greater wing of the sphenoid, which contributed to severe reduction of orbital volume and protrusion of the eyeglobe. Orbital volume was further reduced by maxillary hypoplasia in all three planes of space together with retrognathia. Maxillary height was extremely short and so was the nose. The width of the nasal cavity, height and depth of the bony nasopharynx, and the nasopharyngeal airway were all markedly reduced in size. The mandible was of fairly normal size and shape but was posteriorly inclined. Head posture was extended in relation to the cervical column. Total facial height was increased, whereas upper facial height was markedly reduced. Incisor occlusion showed mandibular overjet and open bite. Apert syndrome patients were then compared to a group of Crouzon syndrome patients. Marked and significant differences were found between the two syndromes in nearly all craniofacial regions, and craniofacial dysmorphology was generally more severe in Apert syndrome patients.

Anomalies of craniofacial skeleton and teeth in cleidocranial dysplasia.

Abstract: Mutations involving the transcription factor CBFA1 cause cleidocranial dysplasia (CCD) in man. Recently, a mouse model of CCD has been generated (Cbfal +/-) [Komori et al., 1997], and disturbances of osteoclast differentiation have been documented. It has been shown that these animals exhibit hypoplastic clavicles and nasal bones, and retarded ossification of parietal, interparietal, and supraoccipital bones. Humans with CCD show all these features, including severely retarded ossification of the cranial base, strongly suggesting that both intramembranous ossification and endochondral ossification are affected. In addition, CCD patients have multiple supernumerary teeth and delayed tooth eruption. The present report presents 3D reconstructions of computerised tomography (CT) scans of the craniofacial region of a CCD boy examined at both 1 and 7 years of age. The anomalies in craniofacial skeleton and teeth are analysed and compared to the findings of our previous clinical studies and to the findings in the animal model. Based on the available information, we suggest that osteoblast, osteoclast, and dentinoclast differentiation may be disturbed in CCD.

A comparison of the craniofacial morphology in 2-month-old unoperated infants with unilateral complete cleft lip and palate, and unilateral incomplete cleft lip.

Abstract: This paper reports a cephalometric analysis of the craniofacial morphology in infants with unoperated unilateral complete cleft lip and palate (UCCLP) and unoperated unilateral incomplete cleft lip (UICL). The purpose of the study was to determine the nature and extent of the craniofacial deviations in UCCLP as compared to the morphology in UICL, which has previously been shown to be close to normal. The samples comprised 82 infants with UCCLP (58 males and 24 females) and 75 with UICL (48 males and 27 females). The mean age was about 2 months in both groups. The cephalometric analysis of craniofacial morphology included the lateral, frontal, and axial projections. The data were presented as mean plots of the craniofacial region including the calvaria, cranial base, orbits, nasal bone, maxilla, mandible, cervical column, pharynx, and soft-tissue profile. The most pronounced deviations in the UCCLP group were observed in the maxillary complex and the mandible. The most striking findings were: markedly increased width of the maxilla, a short mandible, and bimaxillary retrognathia except for the premaxillary area, which was relatively protruding and asymmetric. The study did not support the hypothesis previously suggested in the literature that cleft lip and palate is a craniofacial anomaly as size and shape of the calvaria and cranial base were found to be normal. The etiology of cleft lip and palate is still incompletely understood. Based on the present study, we suggest that facial type may be a liability factor that could represent a developmental threshold increasing the probability of cleft lip and palate.

Tracing craniosynostosis to its developmental stage through bone center displacement.

Abstract: In metopic and coronal suture synostosis, the involved bone centers are abnormally situated just next to the affected suture. Bone centers are the starting point of ossification during embryogenesis from which bone growth spreads radially. In this paper, we describe a similar observation for sagittal suture synostosis, with both parietal bone centers located almost completely cranially. The (reduced) distance between the bone centers of a synostotic suture reflects the time during embryogenesis at which fusion took place. We suggest that in craniosynostosis the bone centers arise in their normal position, and initial outgrowth is undisturbed until the bone fronts meet. It is during this developmental stage that fusion occurs instead of suture formation. Due to the fusion, growth can only occur at the free bony rims from then on. The bone centers remain located at a fixed distance from one another in the middle of the fused bones, becoming relatively more displaced with time. This implies that the distance between the involved bone centers directly indicates the developmental period during which sutural growth was arrested. The same phenomenon of bone center displacement is found in types of craniosynostosis with and without fibroblast growth factor receptor (FGFR) or TWIST gene mutations.

Craniofacial features associated with amelogenesis imperfecta.

Abstract: Craniofacial alterations occur with increased frequency in patients with amelogenesis imperfecta (AI). The purpose of this study was to characterize the craniofacial features associated with AI in families from the US. Twenty-seven people with AI and 14 unaffected family members from nine separate kindreds were evaluated. The diagnosis was established by history, clinical, and radiographic examination, and histological and or biochemical analysis of enamel. The kindreds were generally classified as hypoplastic AI (HPAI), hypocalcified AI (HCAI), or hypomaturation AI (HMAI) and then further subclassified based on phenotype and mode of inheritance. Linear and angular cephalometric measures were converted to z-scores using gender/age matched values from the Bolton and Behrent's standards. Statistical analyses included t-tests and ANOVA accepting P < or = 0.05 as significant. The vertical dimension of the lower face was significantly increased (ANSMe; P = 0.001), especially in affected individuals compared with unaffected relatives, in all kindreds with HCAI and HMAI but in only one kindred with autosomal recessive rough AI. Clinically, an anterior open bite (overbite < 0 mm) was observed in 26% of all dentate individuals with AI and none of their unaffected relatives. Skeletal morphology was highly variable depending on the AI type and kindred. While this study shows an association of altered craniofacial morphology with certain AI kindreds, the relationship of the AI genotype to the observed malocclusions remains to be defined.

Occurrence and temporal variation in matrix metalloproteinases and their inhibitors during murine secondary palatal morphogenesis.

Abstract: Extracellular matrix (ECM) molecules are known to play a pivotal role in morphogenesis of the secondary palate, and changes in their composition and distribution, not attributable to changes in synthesis, are known to occur during palatogenesis. The present study was undertaken to determine if the enzymes responsible for mediating their degradation, the matrix metalloproteinases (MMP), and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMP), are temporospatially regulated during murine palatal shelf morphogenesis. Palatal shelves were harvested at gestational days (gd) 12, 13 and 14. MMPs were identified by gelatin zymography, with and without inhibitors, and the identity of specific bands confirmed by Western blot analysis. TIMPs were identified by reverse zymography. MMP and TIMP messages were detected using RT-PCR with specific primers to MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2. Zymography revealed bands of molecular weights corresponding to MMPs 2, 7, 9 and 13 at all ages examined; the intensity of these bands increased with developmental age. Western blot analysis established the presence of MMP-3 and its developmental variation in expression. RT-PCR demonstrated the presence of mRNA for all MMPs and TIMP at all sampling times and all but MMP-2 showed developmental variation. Whereas increases in mRNA were detected for MMPs 3, 9, and 13, MMP-7 mRNA decreased between gd 12 and 14. The results of this study demonstrate that MMPs 2, 3, 7, 9 and 13 and TIMPs 1 and 2 and their messages are present during the course of palatal shelf remodelling and that their expression is temporally regulated.

Craniofacial growth in subjects with unilateral complete cleft lip and palate, and unilateral incomplete cleft lip, from 2 to 22 months of age.

Abstract: This paper reports a longitudinal quantitative cephalometric analysis of the craniofacial growth in subjects with unilateral complete cleft lip and palate (UCCLP), and unilateral incomplete cleft lip (UICL), from 2 to 22 months of age. The purpose of the study was to determine the amount and direction of growth in UCCLP compared to UICL (control group) from 2 months of age (just prior to lip repair) to 22 months of age, 20 months later. The sample comprised of 49 subjects with UCCLP (37 males and 11 females) and 45 with UICL (29 males and 16 females). The cephalometric analysis of the craniofacial morphology included lateral, frontal, and axial projections. The data were presented as mean plots of the craniofacial region including the calvaria, cranial base, orbits, nasal bone, maxilla, mandible, cervical column, pharynx, and soft-tissue profile. A valid common coordinate system (registration according to the n-s line in the lateral projection, latero-orbitale line in the frontal projection, and meatus acusticus externus line in the axial projection for the landmark positions at examination 1 and 2) was ascertained. The growth at a specific anatomical location in a patient was defined as the displacement vector from the coordinate of the corresponding landmark in the X-ray at examination 1 to its coordinate at examination 2, corrected for X-ray magnification. The growth of an anatomical region in a patient was assessed by investigating the growth pattern formed by a collection of individual growth vectors in that region. The amount of growth in the UCCLP and UICL group was very similar. The general craniofacial growth pattern, in terms of the direction of growth, was also fairly similar in the UCCLP group and the control group. However, the maxilla and mandible showed a more vertical growth pattern than that observed in the control group. This study confirms that UCCLP is a localized deviation, and not a craniofacial anomaly, due to the fact that a normal growth potential has been observed in all craniofacial regions, except where the growth had been directly influenced by surgical intervention. Furthermore, the vertical growth pattern of the maxilla and mandible supports the hypothesis of a special facial type in cleft lip and palate individuals, and the facial type as a liability factor increasing the probability of cleft lip and palate.

Pfeiffer syndrome caused by haploinsufficient mutation of FGFR2.

Abstract: Mutations of the fibroblast growth factor receptors (FGFRs) cause several dominantly inherited congenital skeletal disorders and syndromes. Recently, these mutations have been suggested to cause either ligand-independent activation of the receptor or a dominant negative inactivation. The analysis of two Japanese patients with Pfeiffer syndrome and postaxial polydactyly of the hand now shows that both carried the same 1119-2A-to-G transition of the FGFR2 gene and this nonsense mutation caused skipping of exon 9(B) and haploinsufficiency of FGFR2.

Cytochemical identification of HSP110 during early mouse facial development.

Abstract: Apoptotic cell death constitutes a common phenomenon observed during development. This process plays an important role in the regulation of cell populations and in early differentiation of embryonic organs. Several teratologic situations are considered as resulting in a dramatic increase of the apoptotic process. In mammalian cells, heat shock proteins (HSPs), expressed or increased in response to various stresses, act as molecular chaperones in physiological conditions. In order to determine specific histochemical markers of apoptotic cells in normal craniofacial development, we observed the expression of stress proteins (HSPs) 70, 86, and 110. The apoptotic pattern of mesectodermal cell death areas was confirmed using both nuclear staining (Feulgen) and specific labeling of DNA fragmentation (TUNEL). These areas are localized in the proximal parts of the first and second visceral arches. They are located in mesectodermal and ganglionic cells. Apoptotic mesectodermal populations strongly express HSP110, as shown by the cytochemical identification of HSP110 and by double staining HSP110-TUNEL, suggesting that this protein could be considered as a new marker for apoptotic embryonic cells, and could be used in further teratologic studies to better quantify induced cell death.

Positional changes of the frontoparietal ossification centers in perinatal craniosynostotic rabbits.

Abstract: It has been suggested that craniosynostosis is caused by abnormally located ossification centers (i.e., bony tubers) in the developing skull prior to suture formation [Mathijssen et al., 1996, 1997]. The present study was designed to test this hypothesis in a rabbit model of human familial, nonsyndromic coronal suture (CS) synostosis. Calvariae were taken from 99 New Zealand White rabbit perinates (55 normal controls, 15 with delayed-onset CS synostosis, and 29 with bilateral or unilateral CS synostosis), ranging in age from 23 to 34 days postconception (synostosis occurs at approximately 23 days in this model). Frontoparietal, interfrontal, and interparietal ossification center distances were obtained using a Wild microscope with camera lucida attachment and a 2-D computer digitization technique. Linear regression analysis was used to compare age-related changes in the perinatal ossification centers among groups. Results revealed that frontoparietal ossification center regression line slopes had similar start points (24-day intercepts) with significantly (P 0.05) differences were noted in regression line slopes among groups for interparietal or interfrontal ossification center distances. Results demonstrated that, in synostosed perinates, frontoparietal ossification center location was similar to normals around the time of synostosis and became displaced later. These findings suggest that ossification center (i.e., bony tuber) displacement seen in infants with craniosynostosis is probably a secondary and compensatory, postsynostotic change and not a primary causal factor of synostosis in this rabbit model.

Nasal fossa malformations and paramedian facial cleft: new perspectives.

Abstract: Choanal atresia may be associated with other cranio-facial malformations, including various degrees of nasal fossa malformation, and may be a part of paramedian facial clefts (as described by Tessier et al. [1977]). We identified five such cases with combined clinical elements corresponding to Tessier's paramedian facial cleft, including eyelid coloboma, mild to severe choanal and nasal fossa anomalies, ethmoidal hypoplasia and anterior skull base malformation, sometimes with proboscis lateralis and half-nose hypoplasia. These observations incited us, first, to elaborate a conception which accounts for the likely embryological mechanisms involved; second, to propose a new classification based on anatomical and pathogenic embryological considerations; and last, to propose the use of transpalatal approach to restore choanal permeability, since endonasal laser therapy is particularly dangerous in such cases.

GAPO syndrome: a new case of this rare syndrome and a review of the relative importance of different phenotypic features in diagnosis.

Abstract: The case of GAPO syndrome reported here is the 24th recorded case, 23 cases having been published previously. The 29-year-old male under discussion presents all the typical features of the syndrome, having short stature, dysmorphic craniofacial features, total alopecia and pseudoanodontia. Orally, the erupted primary dentition was extremely worn and on radiographic examination, the second mandibular molars were found to be unerupted, together with the entire permanent dentition. Cephalometry revealed the absence of facial pneumatisation, a deficient cranial base with diminished upper face height and maxillary and mandibular hypoplasia with a prognathic skeletal pattern. Histological examination of an extracted primary incisor and its surrounding root bone revealed extensive ankylosis. This paper describes in detail the clinical findings and reviews, and discusses previously published cases in relation to the present one. As with prior cases, parental consanguinity was present in the pedigree.

Soft tissue thin-plate spline analysis of pre-pubertal Korean and European-Americans with untreated Angle's Class III malocclusions.

Abstract: The purpose of this study was to assess soft tissue facial matrices in subjects of diverse ethnic origins with underlying dentoskeletal malocclusions. Pre-treatment lateral cephalographs of 71 Korean and 70 European-American children aged between 5 and 11 years with Angle's Class III malocclusions were traced, and 12 homologous, soft tissue landmarks digitized. Comparing mean Korean and European-American Class III soft tissue profiles, Procrustes analysis established statistical difference (P < 0.001) between the configurations, and this difference was also true at all seven age groups tested (P < 0.001). Comparing the overall European-American and Korean transformation, thin-plate spline analysis indicated that both affine and non-affine transformations contribute towards the total spline (deformation) of the averaged Class III soft tissue configurations. For non-affine transformations, partial warp (PW) 8 had the highest magnitude, indicating large-scale deformations visualized as labio-mental protrusion, predominantly. In addition, PW9, PW4, and PW5 also had high magnitudes, demonstrating labio-mental vertical compression and antero-posterior compression of the lower labio-mental soft tissues. Thus, Korean children with Class III malocclusions demonstrate antero-posterior and vertical deformations of the labio-mental soft tissue complex with respect to their European-American counterparts. Morphological heterogeneity of the soft tissue integument in subjects of diverse ethnic origin may obscure the underlying skeletal morphology, but the soft tissue integument appears to have minimal ontogenetic association with Class III malocclusions.

The effect of growth hormone therapy on craniofacial growth and dental maturity in children with Down syndrome.

Abstract: Craniofacial growth was evaluated 3 years after termination of growth hormone (GH) therapy in ten Down syndrome (DS) children. The control group consisted of 16 age-matched children with DS. The treatment started at 6-9 months of age, and the duration was 36 months. There were no statistically significant differences in craniofacial development between DS children treated with GH or DS children not treated. In conclusion, the results of this study indicate that GH therapy for 36 months in children with DS did not change the craniofacial morphology compared to a group of DS children not given GH.

Confirmation of linkage of Van der Woude syndrome to chromosome 1q32: Evidence of association with STR alleles suggests possible unique origin of the disease mutation

Abstract: Van der Woude syndrome (VWS) is an autosomal dominant craniofacial disorder with high penetrance and variable expression. Its clinical features are variably expressed, but include cleft lip and/or cleft palate, lip pits and hypodontia. All VWS families studied to date map the disease gene to a < 2 cM region of chromosome 1q32, with no evidence of locus heterogeneity. The aim of this study is to refine the localization of the VWS gene and to further assess possible heterogeneity. We analyzed four multiplex VWS families. All available members were clinically assessed and genotyped for 19 short tandem repeat markers on chromosome 1 in the VWS candidate gene region. We performed two-point and multipoint limit of detection (LOD) score analyses using a high penetrance autosomal dominant model. All families showed positive LOD scores without any recombination in the candidate region. The largest two-point LOD score was 5.87. Our assay method for short tandem repeat (STR) markers provided highly accurate size estimation of marker allele fragment sizes, and therefore enabled us to determine the specific alleles segregating with the VWS gene in each of our four families. We observed a striking pattern of STR allele sharing at several closely linked loci among our four Caucasian VWS families recruited at three different locations in the US. These results suggest the possibility of a unique origin for a mutation responsible for many or most cases of VWS.

Remodeling of the sagittal suture in osteopetrotic (op/op) mice associated with cranial flat bone growth.

Abstract: It is well known that cranial flat bone experiences growth and development at the sutural interface, which is regarded as a neutral zone to control mechanical stimuli. In osteopetrotic (op/op) mice, meanwhile, cranial deformation is produced by the deficiency of osteoclasts and the subsequent defect of bone resorption. It would be a reasonable assumption that such disturbance in bone remodeling affects sutural modification and the relevant cranial flat bone development. The present study was thus conducted to examine histological features of the sagittal sutures in op/op mice, with special reference to the relevant bone remodeling. The sagittal sutures in 10-, 15-, 30-, and 60-day-old normal and op/op mice were observed microscopically. Furthermore, osteoclastic activity was evaluated on the sections stained with tartrate-resistant acid phosphatase (TRAP). The sutures of 15-day-old op/op mice showed stenosis and synostosis, and less-developed collagen fibers associated with an irregular arrangement of fibroblasts, whereas these changes were rarely found in normal mice. Osteoclasts were hardly detected in the parietal bones around the sutures of op/op mice, although the number was numerous in normal mice. These results emphasize that congenital deficiency in osteoclast produces unbalanced bone remodeling at the sutural interface and on the surfaces of the cranial bones, which is assumed to be closely related to cranial bone deformity in op/op mice.

High levels of GM1-ganglioside beta-galactosidase in the salivary glands and GM1-like-ganglioside storage in parotids of deficient mice.

Abstract: We have previously demonstrated high levels of GM1-ganglioside beta-galactosidase (beta-gal) in the salivary glands of Swiss-Webster mice (Nowroozi et al., J Craniofac Genet Dev Biol 18:51, 1998), and suggested that this activity reflects an important role for the lysosome in catabolism of salivary glycoconjugates. Here, we characterized and compared activities of lysosomal glycosidases among the salivary glands, spleen, and muscle of C57BL/6 mice, beta-gal hexosaminidase, and beta-glucuronidase activities are high in all three glands relative to muscle. Enzyme activities in the sublingual gland were substantially higher than in the submandibular and parotid glands. Spleen displays levels of activity that are comparable or higher (for beta-glucuronidase) than those in the salivary glands, whereas muscle displays substantially lower levels of these lysosomal glycosidases. In order to investigate the role of beta-gal in the salivary glands, we further characterized the salivary phenotype of knock-out mice deficient in this enzyme, mimicking human GM1-gangliosidosis. In contrast with the relative levels of beta-gal specific-activity among the salivary glands, only the parotid developed severe, generalized, degenerative histopathological changes in beta-gal-deficient knock-out mice. GM1-like-ganglioside, typically found at high levels only in the nerve tissue, where its exact function is still not clear, was demonstrated in storage vacuoles of the parotid glands of the deficient mice by binding of cholera toxin subunit B. Thus, beta-gal activity observed in the parotid gland most likely reflects its role in GM1-ganglioside catabolism, and this ganglioside, never previously reported in the salivary glands, may have a role in parotid exocrine secretory functions. beta-gal may also serve in secretory glycoprotein catabolism in other salivary glands, but this function may be non-essential for these glands.

Craniofacial growth in a whole rat head transplant: how does a non-functional head grow?

Abstract: To evaluate factors intrinsic to the regulation of craniofacial bone growth, we have developed a new experimental model in which the whole head of an infant rat is transplanted to the body of an isohistogenic rat by means of microvascular anastomosis. In our model, the transplanted head has neither scars nor any moving soft tissue that could modify growth around facial bones. Using this model, we evaluated the growth pattern of the craniofacial complex by means of serial roentgenographic cephalometrics. Ten transplantations were performed using 10-day-old rats as donors and 8-week-old rats as recipients. Cephalograms were taken from the lateral direction at 10, 20, 30, and 40 days after transplantation. Several reference points were selected to analyze the growth pattern. In the present study, we conclude that the size and form of the bony complex are mainly determined genetically. There is craniofacial skeletal growth in the absence of muscle function and brain growth. Further, both the nasal cartilage and the sutures appear to be autonomous growth centers having intrinsic growth potential. Genetic or epigenetic information plays an important role at the skeletal level, but it also affects the muscles through the medium of the muscular tonus responsible for posture and other related phenomena.

Lack of the bone remodeling in osteopetrotic (op/op) mice associated with microdontia.

Abstract: Osteopetrosis is an inherited metabolic disease characterized by an excessive accumulation of bone. This is associated with an osteoclast deficiency. Osteopetrosis is always accompanied by the failure and/or delay of tooth eruption. The present study was conducted to examine in detail the morphological and histological changes of growth of the third molars in the osteopetrosis (op/op) mouse. At the age of 10 days, normal and op/op mice showed no detectable difference in the shape of the third molar follicles. However, the third molars in the op/op mouse became obscured by the proliferation of neighboring bone trabeculae. Moreover, no tartrate-resistant acid phosphatase-positive cells were detected on the bone surfaces of 10-day-old op/op mice. Ankylosis between the root dentin and proliferating bone trabeculae was a common feature in the 20- and 30-day-old op/op mice. The third molars erupted into the oral cavity before the age of 30 days in normal mice, and the crowns, roots, and periodontal ligaments appeared well developed. Throughout the experiment, it seemed that the primary cause of the microdontia and ankylosis of the developing root in the mutant mouse was a deficiency of osteoclasts, with attendant lack of bone remodeling.

Optic, olfactory, and vestibular dysmorphogenesis in the homozygous mouse insertional mutant Tg9257.

Abstract: The transgene insertional mutation 9257 on mouse chromosome 18 was originally identified by the circling behavior caused by vestibular abnormalities in heterozygous mutants. To characterize the homozygous phenotype, we generated F2 offspring from the cross (C57BL/6J-tg/+ x DBA/2J). Eye defects ranging in severity from microphthalmia to anophthalmia were observed in the tg/tg offspring. Dysmorphic development of the lens was evident as early as E10.5 in homozygous transgenic mice. Apparent agenesis of the lateral semicircular canal was evident at E14.5. Anomalies of nasomaxillary structures and olfactory neuroepithelium were present in heterozygous and homozygous transgenic mice. The 9257 mutation provides a model for analysis of the morphogenesis of these three neurosensory systems and their associated bony structures.

Morphological change of the nasopremaxillary suture in growing toothless osteopetrotic (op/op) mice

Abstract: Osteopetrotic (op/op) mice are known to commonly show a failure of tooth eruption. It is also well understood that masticatory function is highly associated with the craniofacial morphology of the growing mouse; however, the effects on sutural growth have not been studied. The present study was conducted to examine, in detail, the morphological and histological changes of the nasopremaxillary suture in these mutant mice and to assess a role of mechanical stress from mastication in the sutural growth. The width of the nasopremaxillary suture was measured on the section for the superior (P1), middle (P2), and inferior (P3) levels. The width of the nasopremaxillary suture for the P1 level in the normal mice fed a solid diet was significantly smaller in 30-day-old mice than in 15-day-old mice, whereas the width for the level P3 was significantly greater in the 30-day-old mice than in the 15-day-old mice. These changes in the sutural space were more prominent in the normal mice fed a solid diet than in the normal mice fed a granular diet. The sutural widths for all the levels became smaller in the 30-day-old op/op mice than in the 10-day-old op/op mice. The endocranial area of the nasopremaxillary suture showed synostosis in 30-day-old op/op mice. In both the normal and op/op mice, the number of tartrate-resistant acid phosphatase (TRAP)-positive cells was greatest at the age of 15 days. Moreover, the TRAP-positive cell number was smaller in the op/op mice than in the normal mice for all the experimental stages. Since, in general, mastication begins in mice after tooth eruption, i.e. from 15 to 30 days after birth, the present findings suggest that failure of tooth eruption and the reduced masticatory function restrict sutural modification.

Expression of CSF-1 receptor on TRAP-positive multinuclear cells around the erupting molars in rats.

Abstract: Bone resorption overlying a developing tooth is a necessary event in the creation of an eruption pathway. The formation and function of osteoclasts, which play a major role in bone resorption, are controlled by several factors. Although CSF-1 and its mRNA are expressed in dental follicle cells required for eruption, little is known about the contribution of CSF-1 to osteoclast formation on the bony crypt around the tooth germ. The receptor protein of the CSF-1 encoded proto-oncogene c-fms was identified on multinucleated cells adjacent to the dental follicle, in conjunction with TRAP staining as a marker enzyme for osteoclasts in rat. c-Fms was highly expressed in TRAP-positive multinuclear cells at 3 days postnatal and the number of c-Fms-expressing cells was reduced thereafter. Administration of IL-1alpha, which enhances formation and function of osteoclasts, caused an increase in the number of c-Fms and TRAP-positive cells in rat. On the contrary, injection of calcitonin, which depresses osteoclast formation, caused a decrease in the number. It is obvious that the receptor of CSF-1 is expressed on the surface of osteoclasts around the tooth germ, on the dental follicle. These findings suggested that CSF-1 directly enhances the influx of osteoclasts adjacent to the erupting tooth, resulting in the formation of an eruption pathway.

Ectodermal ablation of the third branchial arch in chick embryos and the morphogenesis of the parathyroid III gland.

Abstract: The parathyroid glands have been classically considered to be derivatives of the third and fourth pharyngeal pouches in most species, including humans. Furthermore, the presence of neural crest-derived cells in the parathyroid glands connective tissue has been apparently established. However, our previous studies have provided a new hypothesis on the origin of these glands in human and chick embryos. To determine the origin of the parathyroid III (P3) gland, ectoderm of the third branchial arch was cauterized in chick embryos at Hamburger and Hamilton's stage 19 (embryonic day 3). Cauterization of the ventral half of the ectoderm was followed by the non-formation, on the same side, of the P3 gland. When the dorsal half of the ectoderm was cauterized, both the right and left P3 glands formed. Our observations suggest that the ectoderm of the ventral half of the third branchial arch is necessary for the organization of the P3 gland.

A new perspective of human origin and dispersals derived from the microevolution of teeth.

Abstract: Recent genetic studies have heightened the expectation that the origin of modern humans will be defined, but one clear vision has yet to be developed. The study of teeth has historically been an informative means to help define human dispersals. Quantitative tooth data is presented encompassing worldwide human populations. A null hypothesis phylogeny developed from the multivariate analysis of the microevolution of the dental phenotype was interpreted to be broadly in accord with the dominant interpretation of genetic, archaeological, and other dental data by showing that the first division in the dispersion of extant humanity was within sub-Sahara Africans; i.e., San, and Western Africans and Bantu. This "out-of-Africa" interpretation of the graphical results suggests that the first modern human African emigrants not to go extinct were Southeast Asian Negritos. All Eurasians then emerged and expanded through a series of extinct antecedent populations branching from the short lineage extending from Negritos to Australian aborigines. Caucasoids were the first group to fission from this stock. Under this hypothesis, the next to have emerged were antecedent Southeast Asians, from which present Southeast Asians and then antecedent east Central Asians then diverged. Independently, people from the region of Mongolia and all Native Americans arose as daughter populations from antecedent east Central Asians. The broad outline of humanity studied here cannot disprove the equally explanatory protean multiregional hypotheses, but with the inclusion of hominids and further modern human populations either parts of the multiregional hypothesis or the outlined more linear evolutionary scenario likely can be refuted.

Facial skeletal growth in growing "toothless" osteopetrotic (op/op) mice: radiographic findings.

Abstract: The defective bone resorption in the osteopetrotic (op/op) mouse brings about failure of tooth eruption. Furthermore, the op/op mouse has been studied as a "toothless" mouse in recent morphological and physiological investigations of the relationship between mastication and masseter muscle development. The present study was conducted to examine in detail the nasal bone and the premaxillary bone in this mutant mouse and to assess the roles of incisor growth and the mechanical stress of mastication in nasal bone and premaxillary bone growth. The forms of the nasal bone and the premaxillary bone were observed using roentgenography in both toothless op/op and normal (control) mice. In the op/op mouse, the nasal bone and the premaxillary bone show remarkable deformity. In contrast, the normal mouse appears well developed. This suggests that growth of the incisor root is important to normal upper jaw growth in the mouse. Furthermore, it is proposed that the upper facial phenotype seen in the op/op mice results from not only decreased bone resorption, but also from absence of the mechanical stress provided by normal mastication.