GATA3 is essential for separating patterning domains during facial morphogenesis

Neural crest cells (NCCs) within the mandibular and maxillary prominences of the first pharyngeal arch are initially competent to respond to signals from either region. However, mechanisms that are only partially understood establish developmental tissue boundaries to ensure spatially correct patterning. In the 'hinge and caps' model of facial development, signals from both ventral prominences (the caps) pattern the adjacent tissues whereas the intervening region, referred to as the maxillomandibular junction (the hinge), maintains separation of the mandibular and maxillary domains. One cap signal is GATA3, a member of the GATA family of zinc-finger transcription factors with a distinct expression pattern in the ventral-most part of the mandibular and maxillary portions of the first arch. Here, we show that disruption of Gata3 in mouse embryos leads to craniofacial microsomia and syngnathia (bony fusion of the upper and lower jaws) that results from changes in BMP4 and FGF8 gene regulatory networks within NCCs near the maxillomandibular junction. GATA3 is thus a crucial component in establishing the network of factors that functionally separate the upper and lower jaws during development.

Assessment of the maxilla-mandible-nasion angle in normal and aneuploid foetuses in the first trimester of pregnancy

PURPOSE

This retrospective study aims to determine whether the maxilla-mandible-nasion (MMN) angle can be reliably measured in the first trimester, to describe normal ranges, and to determine if significant changes occur in foetuses with aneuploidies.

METHODS

The MMN angle was measured in stored 2D-ultrasound images of 200 normal fetal profiles between 11⁺⁰ and 13⁺⁶ weeks of gestation. Each image was analyzed by two observers at two independent time points. Bland-Altmann analysis was performed to evaluate the reliability of the measurements. Additionally, the MMN angle was measured on sonograms from 140 aneuploid foetuses.

RESULTS

The mean MMN angle in normal foetuses from 11 to 14 weeks of gestation was 15.4°. Reliability of the measurement was high when repeatedly measured by the same observer (ICC = 0.92 and 0.82) and between two observers (ICC = 0.77 and 0.63). Average MMN values in foetuses with trisomy 21, 13, and Turner syndrome were significantly higher than those measured in normal foetuses. The highest differences were observed in foetuses with trisomy 13. Among those, 62% had an MMN angle above the 95th percentile and 92% above the normal mean.

CONCLUSION

The MMN angle can be reliably measured in early pregnancy and is abnormal in about 60% of foetuses with trisomy 13.

Absent 'superimposed-line' sign: novel marker in early diagnosis of cleft of fetal secondary palate

OBJECTIVES

To describe a novel sign, the 'superimposed-line' sign, for early diagnosis of cleft of the fetal secondary palate on two-dimensional imaging of the vomeromaxillary junction in the midsagittal view.

METHODS

This was a prospective evaluation of the superimposed-line sign using two-dimensional sonography (midsagittal view) in 9576 singleton fetuses referred for routine screening between 12 and 20 weeks of gestation. In this view, the vomer bone appears as a line superimposed on the distal two-thirds of the maxillary line, as the vomer fuses with the secondary palate in the midline. If there is a midline cleft of the secondary palate, the line formed by the palate is absent and hence only the vomer bone is visualized, creating a single line instead of the normal superimposed double line. Multiplanar three-dimensional (3D) views were assessed in cases in which the superimposed-line sign was absent.

RESULTS

The superimposed line was absent in 17 fetuses with a cleft of the secondary palate that was confirmed by 3D evaluation. Of these, 13 had defects involving the premaxilla and four had an isolated cleft of the secondary palate. Postnatal confirmation was available in all cases. The sign was useful in ruling out cleft of the fetal secondary palate in 32 high-risk cases with a family history of cleft palate. The superimposed-line sign had a sensitivity of 89.5% in detecting cleft of the secondary palate.

CONCLUSIONS

The superimposed-line sign is a new sonographic marker for evaluation of cleft of the fetal secondary palate; documentation of this sign proves the presence of both the palate and vomer in the midline. This marker can be demonstrated clearly in the late first trimester, allowing early diagnosis of secondary palatine cleft. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

[Diagnostic and therapeutic interest of studying the nose in maxillo-dento-facial orthopedics]

INTRODUCTION

Orthodontists have long tried to predict future growth. It is one of the most difficult goals to achieve precisely despite the different methods of growth forecasting. A simple technique based on clinical and radiological analyses of the nose and premaxilla makes it possible, using no measurements, to accurately predict future maxillary growth and to deduce the therapeutic indications. A morphologic study of the nose is also an important item in the diagnosis of cranio-facial syndromes.

MATERIALS AND METHODS

Combining detailed semiologic and radiologic studies of the nasal and premaxillary structures, this article proposes a method for evaluating and predicting facial growth.

RESULTS

Experience based on many observations and current embryological knowledg can detect growth abnormalities of the ethmoïdo-nasal-premaxillary unit and provide valuable therapeutic information.

DISCUSSION

Combining clinical and radiologic analyses of nasal and premaxillary morphology is a good method to predict growth of the upper face. It is also an important feature in the diagnosis of cranio-facial syndromes.

CONCLUSION

This technique should be included in the diagnosis of maxillo-dento-facial orthopedic cases.

Essential Role of Nr2f Nuclear Receptors in Patterning the Vertebrate Upper Jaw

The jaw is central to the extensive variety of feeding and predatory behaviors across vertebrates. The bones of the lower but not upper jaw form around an early-developing cartilage template. Whereas Endothelin1 patterns the lower jaw, the factors that specify upper-jaw morphology remain elusive. Here, we identify Nuclear Receptor 2f genes (Nr2fs) as enriched in and required for upper-jaw formation in zebrafish. Combinatorial loss of Nr2fs transforms maxillary components of the upper jaw into lower-jaw-like structures. Conversely, nr2f5 misexpression disrupts lower-jaw development. Genome-wide analyses reveal that Nr2fs repress mandibular gene expression and early chondrogenesis in maxillary precursors. Rescue of lower-jaw defects in endothelin1 mutants by reducing Nr2f dosage further demonstrates that Nr2f expression must be suppressed for normal lower-jaw development. We propose that Nr2fs shape the upper jaw by protecting maxillary progenitors from early chondrogenesis, thus preserving cells for later osteogenesis.

Phenotypic Changes in Dentition of Runx2 Homozygote-null Mutant Mice

Genetic and molecular studies in humans and mice indicate that Runx2 (Cbfa1) is a critical transcriptional regulator of bone and tooth formation. Heterozygous mutations in Runx2 cause cleidocranial dysplasia (CCD), an inherited disorder in humans and mice characterized by skeletal defects, supernumerary teeth, and delayed eruption. Mice lacking the Runx2 gene die at birth and lack bone and tooth development. Our extended phenotypic studies of Runx2 mutants showed that developing teeth fail to advance beyond the bud stage and that mandibular molar organs were more severely affected than maxillary molar organs. Runx2 (−/−) tooth organs, when transplanted beneath the kidney capsules of nude mice, failed to progress in development. Tooth epithelial-mesenchymal recombinations using Runx2 (+/+) and (−/−) tissues indicate that the defect in mesenchyme cannot be rescued by normal dental epithelium. Finally, our molecular analyses showed differential effects of the absence of Runx2 on tooth extracellular matrix (ECM) gene expression. These data support the hypothesis that Runx2 is one of the key mesenchymal factors that influences tooth morphogenesis and the subsequent differentiation of ameloblasts and odontoblasts.

Maxillary gap at 11-13 weeks' gestation: marker of cleft lip and palate

OBJECTIVE

To describe a new sign of cleft lip and palate (CLP), the maxillary gap, which is visible in the mid-sagittal plane of the fetal face used routinely for measurement of nuchal translucency thickness.

METHODS

This was a retrospective study of stored images of the mid-sagittal view of the fetal face at 11-13 weeks' gestation in 86 cases of CLP and 86 normal controls. The images were examined to determine if a maxillary gap was present, in which case its size was measured.

RESULTS

In 37 (43.0%) cases of CLP the defect was isolated and in 49 (57.0%) there were additional fetal defects. In the isolated CLP group, the diagnosis of facial cleft was made in the first trimester in nine (24.3%) cases and in the second trimester in 28 (75.7%). In the group with additional defects, the diagnosis of facial cleft was made in the first trimester in 46 (93.9%) cases and in the second trimester in three (6.1%). A maxillary gap was observed in 96% of cases of CLP with additional defects, in 65% of those with isolated CLP and in 7% of normal fetuses. There was a large gap (>1.5 mm) or complete absence of signals from the maxilla in the midline in 69% of cases of CLP with additional defects, in 35% of those with isolated CLP and in none of the normal controls.

CONCLUSIONS

The maxillary gap is a new simple marker of possible CLP, which could increase the detection rate of CLP, especially in isolated cases.

The Hox gene Dfd controls organogenesis by shaping territorial border through regulation of basal DE-Cadherin distribution

Hox genes are highly conserved selector genes controlling tissue identity and organogenesis. Recent work indicates that Hox genes also controls cell segregation and segmental boundary in various species, however the underlying cellular mechanisms involved in this function are poorly understood. In Drosophila melanogaster, the Hox gene Deformed (Dfd) is required for specification and organogenesis of the adult Maxillary (Mx) palp. Here, we demonstrate that differential Dfd expression control Mx morphogenesis through the formation of a physical boundary separating the Mx field and the Peripodial Epithelium (PE). We show that this boundary relies on DE-cadherin (DE-cad) basal accumulation in Mx cells controlled by differential Dfd expression. Indeed, Dfd controls boundary formation through cell autonomous basal redistribution of DE-cad which leads to subsequent fold at the Dfd expression border. Finally, the loss of Mx DE-cad basal accumulation and hence of Mx-PE folding is sufficient to prevent Mx organogenesis thus revealing the crucial role of boundaries in organ differentiation. Altogether, these results reveal that Hox coordination of tissue morphogenesis relies on boundary fold formation through the modulation of DE-cad positioning.

Measurement of fetal maxillary and mandibular angles for first-trimester prenatal screening among Taiwanese women

BACKGROUND

Early fetal structure evaluation is crucial. Fetal abnormalities might indicate chromosomal anomalies or abnormal fetal growth. The aim of this study was to establish the appropriate reference range of maxillary and mandibular angles among the Taiwanese population at 11(+0)-13(+6) weeks of gestation in normal singleton pregnancy as reference values for prenatal ultrasonographic examinations.

METHODS

Fetal ultrasonographic data on maxillary angles and mandibular angles at a gestational age ranging from 11(+0) weeks to 13(+6) weeks were recorded in this study. Maternal background and pregnancy outcome were obtained from hospital records.

RESULTS

A total of 87 patients were included in this study. Maxillary and mandibular angles were successfully recorded in 87 (100%) and 84 (96.6%) patients, respectively. The mean maternal age was 31 (range, 19-41) years, with a corresponding gestational age of 12(+4) (range, 11(+0)-13(+6)) weeks. The maxillary and mandibular angles were 79.9° ± 15.6° and 71.0° ± 12.8°, respectively. First-degree correlation was not found to exist between gestational age and maxillary and mandibular angles.

CONCLUSION

Normative data for ultrasonographic measurements of maxillary and mandibular angles among the Taiwanese population are presented. Our results may serve as reference values in congenital anomaly screening during prenatal examination.

Jagged1 is essential for osteoblast development during maxillary ossification

Maxillary hypoplasia occurs due to insufficient maxillary intramembranous ossification, leading to poor dental occlusion, respiratory obstruction and cosmetic deformities. Conditional deletion of Jagged1 (Jag1) in cranial neural crest (CNC) cells using Wnt1-cre; Jagged1(f/f) (Jag1CKO) led to maxillary hypoplasia characterized by intrinsic differences in bone morphology and density using μCT evaluation. Jag1CKO maxillas revealed altered collagen deposition, delayed ossification, and reduced expression of early and late determinants of osteoblast development during maxillary ossification. In vitro bone cultures on Jag1CKO mouse embryonic maxillary mesenchymal (MEMM) cells demonstrated decreased mineralization that was also associated with diminished induction of osteoblast determinants. BMP receptor expression was dysregulated in the Jag1CKO MEMM cells suggesting that these cells were unable to respond to BMP-induced differentiation. JAG1-Fc rescued in vitro mineralization and osteoblast gene expression changes. These data suggest that JAG1 signaling in CNC-derived MEMM cells is required for osteoblast development and differentiation during maxillary ossification.

Cephalometric investigation of craniomaxillofacial structures during the prenatal period: a cadaver study

INTRODUCTION

We aimed to investigate the morphometric development of the cranial base and its related structures, and their growth rate changes from the ninth gestational week to full term in a large group of human fetuses.

METHODS

We selected 203 (109 male, 94 female) fetuses between 9 and 40 weeks of gestation and without any external anomalies. From each fetus, standard lateral and posteroanterior cephalometric images were taken using a dental digital panoramic and cephalometric x-ray machine. Fourteen linear and 9 angular parameters were measured.

RESULTS

The cranial base angle showed a statistically significant increase between the groups from only the second to the third trimester periods. The sagittal translation of the maxilla increased during the prenatal period, whereas the mandibular sagittal relation grew at a steady rate. The vertical plane angles of the maxilla and the mandible did not show any significant changes. The maxillary length to mandibular length ratio remained stable.

CONCLUSIONS

The cranial base angle increased, especially in the second through the third trimesters. The maxilla and the mandible demonstrated different growth patterns in the sagittal direction. The findings of this study could be a guide for interpreting the relationships among the craniofacial structures.

Id2 controls chondrogenesis acting downstream of BMP signaling during maxillary morphogenesis

Maxillofacial dysmorphogenesis is found in 5% of the population. To begin to understand the mechanisms required for maxillofacial morphogenesis, we employed the inhibitors of the differentiation 2 (Id2) knock-out mouse model, in which Id proteins, members of the regulator of basic helix-loop-helix (bHLH) transcription factors, modulate cell proliferation, apoptosis, and differentiation. We now report that spatially-restricted growth defects are localized at the skull base of Id2 KO mice. Curiously, at birth, neither the mutant Id2 KO nor wild-type (WT) mice differed, based upon cephalometric and histological analyses of cranial base synchondroses. In postnatal week 2, a narrower hypertrophic zone and an inhibited proliferative zone in presphenoid synchondrosis (PSS) and spheno-occipital synchondrosis (SOS) with maxillary hypoplasia were identified in the Id2 mutant mice. Complementary studies revealed that exogenous bone morphogenetic proteins (BMPs) enhanced cartilage growth, matrix deposition, and chondrocyte proliferation in the WT but not in the mutant model. Id2-deficient chondrocytes expressed more Smad7 transcripts. Based on our results, we assert that Id2 plays an essential role, acting downstream of BMP signaling, to regulate cartilage formation at the postnatal stage by enhancing BMP signals through inhibiting Smad7 expression. As a consequence, abnormal endochondral ossification was observed in cranial base synchondroses during the postnatal growth period, resulting in the clinical phenotype of maxillofacial dysmorphogenesis.

Developmental patterns of Ki-67, bcl-2 and caspase-3 proteins expression in the human upper jaw

The distribution of the Ki-67, bcl-2 and caspase-3 proteins was immunohistochemically analyzed in the developing human upper jaw (5th-10th gestational weeks). During this period, proliferative activity gradually decreased from higher levels at the earliest stages (50-52%) to lower levels, both in the jaw ectomesenchyme and in the epithelium. The highest expression of bcl-2 protein was found in the epithelium and ectomesenchyme of areas displaying lower rates of cell proliferation. High levels of caspase-3 protein were detected during the earliest stages of jaw development, indicating an important role for apoptosis in morphogenesis of early derivatives of the maxillary prominences. The number of Ki-67, bcl-2 and caspase-3 positive cells changed in a temporally and spatially restricted manner, coincidently with upper jaw differentiation. While apoptosis might control cell number, bcl-2 could act in suppression of apoptosis and enhancement of cell differentiation. A fine balance between cell proliferation (Ki-67), death (caspase-3) and cell survival (bcl-2) characterized early human upper jaw development. A rise in the number of apoptotic cells always temporally coincided with the decrease in number of surviving bcl-2 positive cells within the palatal region. Therefore, the upper jaw development seems to be controlled by the precisely defined expression of genes for proliferation, apoptosis and cell survival.

Maxilla-nasion-mandible angle: a new method to assess profile anomalies in pregnancy

OBJECTIVES

To collect normative data and test the feasibility and reproducibility of measurement of the maxilla-nasion-mandible (MNM) angle between 16 and 36 weeks' gestation and its diagnostic ability in a group of pathological cases.

METHODS

The MNM angle is defined as the angle between the intersection of the maxilla-nasion and mandible-nasion lines in the exact mid-sagittal plane. After assessing reproducibility, the MNM angle was measured in 3D volumes in 241 fetuses cross-sectionally and in 11 fetuses longitudinally. The MNM angle was then tested in 18 pathological cases with facial malformations or syndromes with specific facial features.

RESULTS

The MNM angle could be measured in 92.3% of normal fetuses. Intra- and interobserver intraclass correlation coefficient (ICC) variability was 0.92 and 0.81, respectively. The difference between paired measurements performed by one or two observers was less than 2.5° and 3.6°, respectively in 95% of the cases. The mean MNM angle was 13.5° and did not change significantly during pregnancy (r = - 0.08, P = 0.25). The MNM angle was above the 95(th) centile in all cases of retrognathia and maxillary alveolar ridge interruption. The MNM angle was below the 5(th) centile in Apert syndrome, thanatophoric dysplasia and in two of the three Down syndrome cases.

CONCLUSIONS

The feasibility and reproducibility of measurement of the MNM angle is good. The MNM angle can be used to evaluate the convexity of the fetal profile by enabling an objective assessment of the anteroposterior relationship of the jaws and it may therefore be of help in the diagnosis of retrognathia, maxillary alveolar ridge interruption and flat profile.

Frontomaxillary facial angle in fetuses with spina bifida at 11-13 weeks' gestation

OBJECTIVE

To determine whether in fetuses with open spina bifida at 11-13 weeks' gestation the frontomaxillary facial angle is decreased.

METHODS

The frontomaxillary facial angle was measured in 20 fetuses with open spina bifida and in 100 normal controls matched for crown-rump length (CRL) at 11 + 0 to 13 + 6 weeks and the values in the two groups were compared.

RESULTS

In the control group the frontomaxillary facial angle decreased significantly with CRL from a mean of 84.0 degrees at a CRL of 45 mm to 76.5 degrees at a CRL of 84 mm (SD, 3.26 degrees). In the spina bifida group the mean frontomaxillary facial angle, corrected for CRL, was 9.9 degrees lower than in the controls and it was below the 5(th) centile in 18 (90%) of the cases (P < 0.0001).

CONCLUSIONS

In fetuses with open spina bifida at 11-13 weeks' gestation the frontomaxillary facial angle is decreased and this measurement may be useful in early screening for this abnormality.

Learning curve in measurement of fetal frontomaxillary facial angle at 11-13 weeks of gestation

OBJECTIVE

To determine the number of ultrasound examinations required to train sonographers to accurately measure the fetal frontomaxillary facial (FMF) angle at 11-13 weeks of gestation.

METHODS

Eight sonographers accredited for nuchal translucency thickness (NT) measurement (and with different levels of experience) were trained to measure the fetal FMF angle using specially acquired three-dimensional (3D) volumes. Training was provided in cycles, and each cycle consisted of a training period on 20 randomly selected cases followed by an examination using 10 randomly selected cases. During training, the sonographer was informed of the true FMF angle value after each FMF angle measurement on a case-by-case basis. During examination, the difference between the measured and the true values of the FMF angle (i.e. the delta angle) was calculated. A measurement was considered accurate if the delta angle was less than 5 degrees . The sonographer was considered to be competent and the training finished if all 10 examination cases satisfied this criterion. Otherwise, the sonographer would undergo further cycles of training-examination, until he/she became competent.

RESULTS

The number of training cases required for a sonographer to become competent was 40 for two sonographers, 60 for one, 80 for one, 100 for two, 120 for one and 140 for one, with a median of 90. The median number of failed cases reduced from 2.5 (out of 10) at the first cycle to 0 by the 7(th) cycle. As training cycles increased, the mean angle deviation and measurement time required both reduced significantly. The average delta angle of the passing examination cycle was 2.06 +/- 1.40 degrees . The number of training cases required to become competent in FMF angle measurement was 40 for the two most experienced trainees and 80, 120 and 140 for the three least experienced ones.

CONCLUSIONS

We have demonstrated that competence in FMF angle measurement was achieved after a median number of 90 cases, with a range of up to 140. The number required was substantially lower, at 40 cases, among those with extensive experience of NT measurement.

Retronasal triangle: a sonographic landmark for the screening of cleft palate in the first trimester

OBJECTIVES

To describe a new first-trimester sonographic landmark, the retronasal triangle, which may be useful in the early screening for cleft palate.

METHODS

The retronasal triangle, i.e. the three echogenic lines formed by the two frontal processes of the maxilla and the palate visualized in the coronal view of the fetal face posterior to the nose, was evaluated prospectively in 100 consecutive normal fetuses at the time of routine first-trimester sonographic screening at 11 + 0 to 13 + 6 weeks' gestation. In a separate study of five fetuses confirmed postnatally as having a cleft palate, ultrasound images, including multiplanar three-dimensional views, were analyzed retrospectively to review the retronasal triangle.

RESULTS

None of the fetuses evaluated prospectively was affected by cleft lip and palate. During their first-trimester scan, the retronasal triangle could not be identified in only two fetuses. Reasons for suboptimal visualization of this area included early gestational age at scanning (11 weeks) and persistent posterior position of the fetal face. Of the five cases with postnatal diagnosis of cleft palate, an abnormal configuration of the retronasal triangle was documented in all cases on analysis of digitally stored three-dimensional volumes.

CONCLUSIONS

This study demonstrates the feasibility of incorporating evaluation of the retronasal triangle into the routine evaluation of the fetal anatomy at 11 + 0 to 13 + 6 weeks' gestation. Because fetuses with cleft palate have an abnormal configuration of the retronasal triangle, focused examination of the midface, looking for this area at the time of the nuchal translucency scan, may facilitate the early detection of cleft palate in the first trimester.

Arsenate-induced apoptosis in murine embryonic maxillary mesenchymal cells via mitochondrial-mediated oxidative injury

BACKGROUND

Arsenic is a ubiquitous element that is a potential carcinogen and teratogen and can cause adverse developmental outcomes. Arsenic exerts its toxic effects through the generation of reactive oxygen species (ROS) that include hydrogen peroxide (H(2)O(2)), superoxide-derived hydroxyl ion, and peroxyl radicals. However, the molecular mechanisms by which arsenic induces cytotoxicity in murine embryonic maxillary mesenchymal (MEMM) cells are undefined.

METHODS

MEMM cells in culture were treated with different concentrations of pentavalent sodium arsenate [As (V)] for 24 or 48 hr and various end points measured.

RESULTS

Treatment of MEMM cells with the pentavalent form of inorganic arsenic resulted in caspase-mediated apoptosis, accompanied by generation of ROS and disruption of mitochondrial membrane potential. Treatment with caspase inhibitors markedly blocked apoptosis. In addition, the free radical scavenger N-acetylcysteine dramatically attenuated arsenic-mediated ROS production and apoptosis, and exposure to arsenate increased Bax and decreased Bcl protein levels in MEMM cells.

CONCLUSIONS

Taken together, these findings suggest that in MEMM cells arsenate-mediated oxidative injury acts as an early and upstream initiator of the cell death cascade, triggering cytotoxicity, mitochondrial dysfunction, altered Bcl/Bax protein ratios, and activation of caspase-9.

Bilateral cleft lip and palate without premaxillary protrusion is associated with lethal aneuploidies

OBJECTIVE

To investigate the clinical implications of two categories of fetal bilateral cleft lip and palate (BCLP): with premaxillary protrusion and with a flattened profile.

METHODS

This was a retrospective study of fetuses with a prenatal diagnosis of BCLP at the Department of Obstetrics and Gynecology of the University of Bologna in the period 1991-2005.

RESULTS

BCLP was diagnosed prenatally in 14 cases (mean gestational age at diagnosis, 21 (range, 12-36) weeks). In nine of these, there was a premaxillary pseudomass; in the remaining five, the profile was flat. Associated structural and/or chromosomal anomalies were found in two of the nine with a premaxillary pseudomass and in all five of those with a flat profile (P = 0.02). All fetuses with a flat profile had aneuploidies (three trisomy 18, one trisomy 13, one trisomy 8 mosaic), as did one of the nine with a premaxillary pseudomass. Eight of the pregnancies were terminated, including three of those with a premaxillary pseudomass and all five of those without. All continuing pregnancies resulted in live births, although one neonate affected by Krabbe's disease died shortly after birth.

CONCLUSIONS

Our findings suggest that a third of cases of BCLP diagnosed in utero have a flat profile and these are at high risk of lethal aneuploidies.

Effects of induced premaxillary suture fusion on the craniofacial morphology in growing rats

OBJECTIVE

Due to premaxillary rapid development and fusion with the maxilla at the fetus stage, the functions of the premaxillary suture still remain unclear. This study was designed to explore the effect of artificial induced premaxillary suture fusion on craniofacial morphology.

METHODS

Thirty Sprague Dawley rats were divided into control and experimental groups, with 3 week, 5 week and 8 week subgroups of five animals each. An incision was made in each rat along the premaxillary suture and cyanoacrylate was administered to immobilize the exposed premaxillary suture for experimental rats. No glue was applied to controls. Weights, dental impressions and radiographs were taken before and after surgery until sacrifice and used to determine the differences between groups using the one-way ANOVA test.

RESULTS

After immobilizing the premaxillary suture, significant changes in the craniofacial morphology were measured at the different time points. In the experimental groups, local changes occurred at the 3rd week. A global alteration in craniofacial morphology was apparent at the 8th week in the experimental group compared to the control. At each successive time point, craniofacial morphological alterations increased in rats with fused premaxillary sutures.

CONCLUSIONS

Induced premaxillary suture fusion can inhibit the growth of the premaxilla and cause extensive craniofacial morphological changes. These findings suggest that premaxillary suture fusion may be related to craniofacial malformation or malocclusion and to the formation of the flattened craniofacial profile in humans.

Frontomaxillary and mandibulomaxillary facial angles at 11 + 0 to 13 + 6 weeks in fetuses with trisomy 18

OBJECTIVE

To define the relative position of the maxilla and mandible in fetuses with trisomy 18 at 11 + 0 to 13 + 6 weeks of gestation.

METHODS

A three-dimensional (3D) volume of the fetal head was obtained before karyotyping at 11 + 0 to 13 + 6 weeks of gestation in 36 fetuses subsequently found to have trisomy 18, and 200 chromosomally normal fetuses. The frontomaxillary facial (FMF) angle and the mandibulomaxillary facial (MMF) angle were measured in a mid-sagittal view of the fetal face.

RESULTS

In the chromosomally normal group both the FMF and MMF angles decreased significantly with crown-rump length (CRL). In the trisomy 18 fetuses the FMF angle was significantly greater and the angle was above the 95(th) centile of the normal range in 21 (58.3%) cases. In contrast, in trisomy 18 fetuses the MMF angle was significantly smaller than that in normal fetuses and the angle was below the 5(th) centile of the normal range in 12 (33.3%) cases.

CONCLUSIONS

Trisomy 18 at 11 + 0 to 13 + 6 weeks of gestation is associated with both mid-facial hypoplasia and micrognathia or retrognathia that can be documented by measurement of the FMF angle and MMF angle, respectively.

Skeletal units of the human embryonic mandible

The development of the mandible was traced on serial sections of 20 human embryos aged 5-8 weeks (developmental stages 13-23). Special consideration was given to the differentiation of skeletal units proposed by Sperber. The first skeletal units, namely the mandibular body, the alveolar unit and the condylar unit, may be distinguished in the 7(th) week. The primordia of all units are identified by the end of the embryonic period (8 weeks).

Experimental induction of palate shelf elevation in glutamate decarboxylase 67-deficient mice with cleft palate due to vertically oriented palatal shelf

BACKGROUND

Gamma-aminobutyric acid is an inhibitory neurotransmitter, synthesized by two isoforms of glutamate decarboxylase (GAD), GAD65 and -67. Unexpectedly, inactivation of GAD67 induces cleft palate in mice. Reduction of spontaneous tongue movement resulting from decreased motor nerve activity has been related to the development of cleft palate in GAD67(-/-) fetuses. In the present study, development of cleft palate was examined histologically and manipulated with culture of the maxilla and partial resection of fetal tongue.

METHODS

GAD67(-/-) mice and their littermates were used. Histological examination and immunohistochemistry were performed conventionally. Organ culture of the maxilla was carried out as reported previously. Fetuses were maintained alive under anesthesia and tips of their tongues were resected.

RESULTS

Elevation of palatal shelves, the second step of palate formation, was not observed in GAD67(-/-) mice. In wild-type mice, GAD67 and gamma-aminobutyric acid were not expressed in the palatal shelves, except in the medial edge epithelium. During 2 days of culture of maxillae dissected from E13.5-E14.0 GAD67(-/-) fetuses, elevation and fusion of the palatal shelves were induced. When E13.5-15.5 mutant fetuses underwent partial tongue resection, the palatal shelves became elevated within 30 min.

CONCLUSIONS

These results suggest that the potential for palate formation is maintained in the palatal shelves of GAD67(-/-) fetuses, but it is obstructed by other, probably neural, factors, resulting in cleft palate.

Temporospatial localization of acetylcholinesterase activity in the dental epithelium during mouse tooth development

Acetylcholinesterase (AChE), a principal modulator of cholinergic neurotransmission, also has been demonstrated to be involved in the morphogenetic processes of neuronal and non-neuronal tissues. This study shows that AChE exhibits temporospatial activity in the dental epithelium of the developing mouse tooth. To identify the AChE activity in the mouse tooth during development, we performed enzyme histochemistry on the mouse embryos from embryonic day 13 (E13) to E18 and on the incisors and molars of the neonatal mouse at 10 days after birth (P10). In the developing molars of mouse embryos, AChE activity was not found in the dental epithelium at E13 (bud stage). AChE activity first appeared in the developing cervical loops of the enamel organ at E14 (cap stage), but was not found in the enamel knot. At E18 (bell stage), AChE activity was localized in the inner enamel epithelium except the cervical-loop area. In the incisors and molars of neonatal mice (P10), AChE activity was localized in the inner enamel epithelium of the cervical-loop and enamel-free area. Overall, AChE activity was localized in the differentiating dental epithelium while the activity of butyrylcholinesterse, another cholinesterase, was located primarily in the cells of the dental follicle. The results suggest that AChE may play a role in the histo- and cytodifferentiation of dental epithelium during tooth development.

Early development of the lower deciduous dentition and oral vestibule in human embryos

The aim of this work was to investigate the early development of the deciduous dentition and oral vestibule in the human embryonic lower jaw. Histological sections and three-dimensional reconstructions from prenatal weeks 6-9 were used. A continuous anlage for the oral vestibule did not exist in the mandible. In contrast to the upper jaw, where we previously observed that the dental and vestibular epithelia developed separately, two dento-vestibular bulges differentiated in the incisor region of the mandible. The lingual parts of each bulge were found to give rise to the respective central and lateral incisors, whereas the labial parts differentiated into the vestibular epithelium. In the canine and molar areas, the dental and vestibular epithelia originated separately. Later, the segments of the vestibular epithelium fused into the labial vestibular ridge, giving rise to the lower oral vestibule in the lip region. In the cheek region, the oral vestibule was found to originate in the mucosal inflection between the developing jaw and the cheek. A similar heterogeneous developmental base for the oral vestibule was also observed in the upper jaw. There is thus no general scheme for the early development of the dental and vestibular epithelia that applies to both the upper and lower jaws, and to both their anterior and posterior regions.

Studies of craniofacial development in rotating bioreactors

Several studies in our laboratory assessed the effect of 3-D culture in various rotating bioreactors on craniofacial development. Initially, mouse first branchial arches were cultured. Molar and incisor development occurred in both upper and lower jaws, but maxilla development was deficient because no brain was present. In a second study using excised whole heads, the oral epithelia fused and teeth did not develop. External structure of the face was obliterated, although internally, eye development was excellent. To preserve both internal spaces and external face structure, subsequent experiments used heads encapsulated in alginate. Teeth developed in these heads, though some interior components were necrotic. Additional experiments used older embryos, with already initiated structures, and less concentrated alginate. Orientation and unreserved identification of structures remain unresolved issues. Future studies will identify structures of interest using transcription factors unique to these structures at particular stages of fetal development.

Frontomaxillary facial angle at 11 + 0 to 13 + 6 weeks: effect of plane of acquisition

OBJECTIVE

To determine the range of positions of the fetal head in which a three-dimensional (3D) volume is acquired for subsequent successful assessment of the frontomaxillary facial (FMF) angle.

METHOD

We obtained 3D volumes of the fetal head at 11 + 0 to 13 + 6 weeks. The volumes were acquired with the head in different positions and reconstructed to obtain a mid-sagittal section and demonstrate the maxilla, palate and frontal bone, which constitute the landmarks for the assessment of the FMF angle.

RESULTS

In the reconstructed mid-sagittal sections, it was possible to demonstrate the landmarks that define the FMF angle in most of the cases when the 3D volume acquisition plane was: (a) mid-sagittal, with the angle between the face of the transducer and the direction of the fetal nose being about 0-99 degrees, 150-199 degrees and 330-359 degrees; (b) transverse at the level of the biparietal diameter when the angle between the transducer and the midline echo of the brain was 0-29 degrees; and (c) oblique around the crown-rump axis when the angle from the mid-sagittal plane was 0-49 degrees. However, the measurement of the FMF angle was artificially increased when in the mid-sagittal plane the angle was 40-99 degrees and 150-199 degrees.

CONCLUSION

Successful assessment of the FMF angle by 3D ultrasound is dependent on the plane and angle of the volume acquisition.

Functional analysis of CBP/p300 in embryonic orofacial mesenchymal cells

CREB binding protein (CBP) and the close structural homolog, p300, are nuclear coactivators of multiple signaling pathways that play important roles in embryonic development and cellular homeostasis. TGFbeta regulates the proliferation rate of many cell types and has been demonstrated to inhibit the growth rate of mouse embryonic maxillary mesenchymal (MEMM) cells. The role of CBP and p300 in TGFbeta-mediated control of proliferation of MEMM cells was thus investigated using an in vitro gene knockdown approach. TGFbeta reporter assays demonstrated that p300 mRNA knockdown via targeted siRNAs led to a reduction in the response to TGFbeta, whereas knockdown of CBP by the same approach had an insignificant effect. In MEMM cell proliferation assays, siRNA-mediated knockdown of CBP and/or p300 had little impact upon TGFbeta-mediated growth inhibition; however, the basal rate of proliferation was increased. Inhibition of p300 activity via overexpression of a dominant-negative mutant (p300deltaC/H3) led to significant inhibition of TGFbeta-mediated activation of p3TP-lux. As with the siRNA knockdown approach, p300deltaC/H3 also increased the basal rate of cell proliferation of MEMM cells. CBP/p300 siRNA knockdown had a significant but incomplete inhibition of TGFbeta-induction of matrix metalloproteinase-9 (gelatinase B) expression. These data demonstrate that p300 is involved in Smad-mediated transcription of p3TP-lux, however, its role (and that of CBP) in biological processes such as the control of cell proliferation and extracellular matrix metabolism is more complex and may be mediated via mechanisms beyond coactivator recruitment.

Frontomaxillary facial angle in fetuses with trisomy 21 at 11-13(6) weeks

OBJECTIVE

The objective of the study was to investigate the location of the front of the maxilla in relation to the forehead in fetuses with trisomy 21 at 11-13 weeks of gestation.

STUDY DESIGN

A three-dimensional volume of the fetal head was obtained before karyotyping in 100 fetuses with trisomy 21 and 300 euploid fetuses. The frontomaxillary facial (FMF) angle, defined as the angle between the upper surface of the upper palate and the frontal bone in a midsagittal view of the fetal face, was measured.

RESULTS

The FMF angle was significantly larger in the trisomy 21 than in the euploid fetuses (mean 88.7 degrees, range 75.4-104 degrees vs mean 78.1 degrees, range 66.6-89.5 degrees, P < .001). The FMF angle was more than 85 degrees in 69% of the trisomy 21 fetuses and in 5% of the euploid fetuses. There was no significant association between the FMF angle and nuchal translucency thickness.

CONCLUSION

Measurement of FMF angle is likely to be a useful adjunct in screening for trisomy 21.

Frontomaxillary facial angle at 11+0 to 13+6 weeks' gestation-reproducibility of measurements

OBJECTIVE

To assess the intra- and interobserver reproducibility in the measurement of the frontomaxillary facial (FMF) angle at 11+0 to 13+6 weeks' gestation and to investigate the effect of deviations from the exact mid-sagittal view on these measurements.

METHODS

Three-dimensional (3D) volumes of the fetal face were used by two operators to measure the FMF angle in 50 chromosomally normal and 50 trisomy 21 fetuses. The measurements were taken in the exact mid-sagittal view and repeated after lateral rotation of the head by 5 degrees, 10 degrees and 15 degrees away from the vertical position of the occipitofrontal diameter axis. Mean difference and 95% limits of agreement between paired measurements of FMF angle by the same and by two different sonographers were determined.

RESULTS

In the mid-sagittal plane the maxillary bone was rectangular shaped. Rotation away from this plane became easily recognizable because at a mean of 7 degrees (range, 4-10 degrees) the shape of the maxilla changed with the appearance of the zygomatic process of the maxilla and at a mean of 8 degrees (range, 4-12 degrees) the tip of the nose became invisible. In both the normal and trisomy 21 fetuses the FMF angle measured at 5-15 degrees was not significantly different from the one measured in the mid-sagittal plane. In 95% of the cases, the difference between paired measurements of the FMF angle by the same sonographer at the mid-sagittal plane was between -2.3 degrees and 3.0 degrees and at 15 degrees it was -1.0 degrees to 6.8 degrees. At the mid-sagittal plane, the difference in measurements between two sonographers was -3.1 to 3.0 degrees.

CONCLUSION

The landmarks that define the mid-sagittal plane of the fetal face are the tip of the nose and the rectangular shaped maxilla. Measurement of the FMF angle is highly reproducible.

Comparative analysis of Hox downstream genes in Drosophila

Functional diversification of body parts is dependent on the formation of specialized structures along the various body axes. In animals, region-specific morphogenesis along the anteroposterior axis is controlled by a group of conserved transcription factors encoded by the Hox genes. Although it has long been assumed that Hox proteins carry out their function by regulating distinct sets of downstream genes, only a small number of such genes have been found, with very few having direct roles in controlling cellular behavior. We have quantitatively identified hundreds of Hox downstream genes in Drosophila by microarray analysis, and validated many of them by in situ hybridizations on loss- and gain-of-function mutants. One important finding is that Hox proteins, despite their similar DNA-binding properties in vitro, have highly specific effects on the transcriptome in vivo, because expression of many downstream genes respond primarily to a single Hox protein. In addition, a large fraction of downstream genes encodes realizator functions, which directly affect morphogenetic processes, such as orientation and rate of cell divisions, cell-cell adhesion and communication, cell shape and migration, or cell death. Focusing on these realizators, we provide a framework for the morphogenesis of the maxillary segment. As the genomic organization of Hox genes and the interaction of Hox proteins with specific co-factors are conserved in vertebrates and invertebrates, and similar classes of downstream genes are regulated by Hox proteins across the metazoan phylogeny, our findings represent a first step toward a mechanistic understanding of morphological diversification within a species as well as between species.

The Prx1 homeobox gene is critical for molar tooth morphogenesis

The paired-related homeobox genes, Prx1 and Prx2, encode transcription factors critical for orofacial development. Prx1(-/-)/Prx2(-/-) neonates have mandibular hypoplasia and malformed mandibular incisors. Although the mandibular incisor phenotype has been briefly described (ten Berge et al., 1998, 2001; Lu et al., 1999), very little is known about the role of Prx proteins during tooth morphogenesis. Since the posterior mandibular region was relatively normal, we examined molar tooth development in Prx1(-/-)/Prx2(-/-) embryos to determine whether the tooth malformation is primary to the loss of Prx protein or secondary to defects in surrounding tissues. Three-dimensional (3D) morphological reconstructions demonstrated that Prx1(-/-)/Prx2(-/-) embryos had molar malformations, including cuspal changes and ectopic epithelial projections. Although we demonstrate that Prx1 protein is expressed only mesenchymally, 3D reconstructions showed important morphological defects in epithelial tissues at the cap and bell stages. Analysis of these data suggests that the Prx homeoproteins are critical for mesenchymal-epithelial signaling during tooth morphogenesis.

21st century neontology and the comparative development of the vertebrate skull

Classic neontology (comparative embryology and anatomy), through the application of the concept of homology, has demonstrated that the development of the gnathostome (jawed vertebrate) skull is characterized both by a fidelity to the gnathostome bauplan and the exquisite elaboration of final structural design. Just as homology is an old concept amended for modern purposes, so are many of the questions regarding the development of the skull. With due deference to Geoffroy-St. Hilaire, Cuvier, Owen, Lankester et al., we are still asking: How are bauplan fidelity and elaboration of design maintained, coordinated, and modified to generate the amazing diversity seen in cranial morphologies? What establishes and maintains pattern in the skull? Are there universal developmental mechanisms underlying gnathostome autapomorphic structural traits? Can we detect and identify the etiologies of heterotopic (change in the topology of a developmental event), heterochronic (change in the timing of a developmental event), and heterofacient (change in the active capacetence, or the elaboration of capacity, of a developmental event) changes in craniofacial development within and between taxa? To address whether jaws are all made in a like manner (and if not, then how not), one needs a starting point for the sake of comparison. To this end, we present here a "hinge and caps" model that places the articulation, and subsequently the polarity and modularity, of the upper and lower jaws in the context of cranial neural crest competence to respond to positionally located epithelial signals. This model expands on an evolving model of polarity within the mandibular arch and seeks to explain a developmental patterning system that apparently keeps gnathostome jaws in functional registration yet tractable to potential changes in functional demands over time. It relies upon a system for the establishment of positional information where pattern and placement of the "hinge" is driven by factors common to the junction of the maxillary and mandibular branches of the first arch and of the "caps" by the signals emanating from the distal-most first arch midline and the lamboidal junction (where the maxillary branch meets the frontonasal processes). In this particular model, the functional registration of jaws is achieved by the integration of "hinge" and "caps" signaling, with the "caps" sharing at some critical level a developmental history that potentiates their own coordination. We examine the evidential foundation for this model in mice, examine the robustness with which it can be applied to other taxa, and examine potential proximate sources of the signaling centers. Lastly, as developmental biologists have long held that the anterior-most mesendoderm (anterior archenteron roof or prechordal plate) is in some way integral to the normal formation of the head, including the cranial skeletal midlines, we review evidence that the seminal patterning influences on the early anterior ectoderm extend well beyond the neural plate and are just as important to establishing pattern within the cephalic ectoderm, in particular for the "caps" that will yield medial signaling centers known to coordinate jaw development.

Tooth Development: 1. Generating Teeth in the Embryo

Teeth are organs that develop in the embryo via a series of interactions between oral epithelium and neural crest-derived ectomesenchyme of the early jaws. These interactions are initiated by the regional production of signalling molecules in the oral epithelium and the transfer of information to the underlying mesenchyme via homeobox gene transcription. This article describes how these interactions are co-ordinated in the embryo during development of the dentition and provides a theoretical basis for the second article in this series; understanding how biologists are attempting to generate teeth artificially in the laboratory.

Proliferation and apoptosis in early molar morphogenesis-- voles as models in odontogenesis

Proliferation and apoptosis play crucial roles in the development of multicellular organisms. Their precise balance is necessary for tissue homeostasis throughout life. The developing dentition is a suitable model to study proliferation and apoptosis during embryogenesis, but the corresponding studies have been carried out principally in the mouse. The present study aimed to examine proliferation and apoptosis in the vole (Microtus sp., Rodentia) during the early morphogenesis of the first upper molar and compare it to what is known from the mouse. To this end, apoptosis and proliferation were investigated using histology and computer-aided 3D reconstruction. Mitoses accumulated predominantly in the developing cervical loop. Apoptosis during early odontogenesis showed highly specific spatio-temporal patterns in the dental epithelium. Apoptotic bodies were localised in non-dividing cell populations. They accumulated in the same places as described in the mouse: antemolar vestiges (ED 12.5 15.5), enamel knot (ED 14.5 15.5), stalk and palatally along the whole first molar tooth germ longitudinal axis (ED 15 - 15.5). Early tooth development in the field vole, including the distribution of apoptosis and mitosis, is very similar to that reported in the mouse, with the exception of the antemolar region. The microtine antemolar vestige is preserved longer than the murine one. It is conceivable that additional distinct differences in morphogenetic processes appear later in tooth development.

Molecular fingerprinting of BMP2- and BMP4-treated embryonic maxillary mesenchymal cells

OBJECTIVE

To determine the differences in gene expression between control-, bone morphogenetic protein (BMP)2- and BMP4-treated murine embryonic maxillary mesenchymal (MEMM) cells.

DESIGN

Transcript profiles of BMP2-, BMP4- and vehicle-treated MEMM cells were compared utilizing the murine high-density GeneChip arrays from Affymetrix. The raw chip data (probe intensities) were pre-processed using robust multichip averaging with GC-content background correction and further normalized with GeneSpring v7.2 software. Cluster analysis of the microarray data was performed with the GeneSpring software. Changes in the gene expression were verified by TaqMan quantitative real-time PCR.

RESULTS

Expression of approximately 50% of the 45 101 genes and expressed sequence tags examined in this study were detected in BMP2-, BMP4- and vehicle-treated MEMM cells and that of several hundred genes was significantly altered (up or downregulated) in these cells in response to BMP2 and BMP4. Expression profiles of each of the 26 mRNAs tested by TaqMan quantitative real-time PCR were found to be consistent with the microarray data. Genes whose expression was modulated following BMP2 or BMP4 treatment, could be broadly classified based on the functions of the encoded proteins such as the growth factors and signaling molecules, transcription factors, and proteins involved in epithelial-mesenchymal interactions, extracellular matrix synthesis, cell adhesion, proliferation, differentiation, and apoptosis.

CONCLUSION

Utilization of the Affymetrix GeneChip microarray technology has enabled us to delineate a detailed transcriptional map of BMP2 and BMP4 responsiveness in embryonic maxillary mesenchymal cells and offers revealing insights into crucial molecular regulatory mechanisms employed by these two growth factors in orchestrating embryonic orofacial cellular responses.

Dual odontogenic origins develop at the early stage of rat maxillary incisor development

Developmental process of rat maxillary incisor has been studied through histological analysis and investigation of tooth-related gene expression patterns at initial tooth development. The tooth-related genes studied here are fibroblast growth factor-8 (Fgf-8), pituitary homeobox gene-2 (Pitx-2), sonic hedgehog (Shh), muscle segment homeobox-1 (Msx-1), paired box-9 (Pax-9) and bone morphogenetic protein-4 (Bmp-4). The genes are expressed in oral epithelium and/or ectomesenchyme at the stage of epithelial thickening to the early bud stage of tooth development. Both the histological observation and tooth-related gene expression patterns during early stage of maxillary incisor development demonstrate that dual odontogenic origins aligned medio-laterally in the medial nasal process develop, subsequently only single functional maxillary incisor dental placode forms. The cascade of tooth-related gene expression patterns in rat maxillary incisor studied here is quite similar to those of the previous studies in mouse mandibular molar, even though the origins of oral epithelium and ectomesenchyme involved in development of maxillary incisor and mandibular molar are different. Thus, we conclude that maxillary incisor and mandibular molar share a similar signaling control of Fgf-8, Pitx-2, Shh, Msx-1, Pax-9 and Bmp-4 genes at the stage of oral epithelial thickening to the early bud stage of tooth development.

[Impacted canine tooth and the eyebrow: the orbit-eyelid impact of occlusal dysfunction]

The orbital region and the dental occlusion are biomechanicaly interdependant. The maxillary basal bone is located in the orbital region due to the presence of the maxillary sinus. Any trouble of the dental occlusion such as a retained canine can involve a lack of projection of the supra and the infra-orbital rim. This lack of projection of the infra-orbital rim is responsible of lower eyelid fat pad; the lack of projection of the supra-orbital rim is responsible of an eyebrow-forehead ptosis. Clinical variations can be observed according to the side of the preeminent eye.

Expression and regulation of the LIM homeodomain gene L3/Lhx8 suggests a role in upper lip development of the chick embryo

LIM-homeodomain (Lhx) genes constitute a gene family that plays critical roles in the control of pattern formation and cell type specification. We have identified a chicken L3/Lhx8 gene, which was widely expressed in the craniofacial region. Whole-mount in situ hybridization showed that L3/Lhx8 mRNA was expressed from stage 15--31 HH in overlapping domains of the maxillary process. Frozen sections revealed these signals in the mesenchyme underneath the epithelium. To determine whether the expression of L3/Lhx8 in the maxillary primordia required signals from the overlying oral epithelium, maxillary processes of stage 23 HH chick embryos were transplanted into the limb bud, in which the mesenchyme was grown in the presence or absence of oral epithelium. The maxillary mesenchyme with epithelium showed significant levels of L3/Lhx8 gene expression. In contrast, no expression of L3/Lhx8 was detected in the epithelium-free mesenchyme. To further explore signaling molecule(s) responsible for Lhx induction, a bead, soaked in either Fgf-8b or TGF-beta3, was implanted into an epithelium-free mesenchymal graft. Both TGF-beta3 and Fgf-8b beads induced expressions of L3/Lhx8 in epithelium-free mesenchymal grafts. Our data suggest that the L3/Lhx8 gene contributes to epithelial mesenchymal interaction in facial morphogenesis and that Fgf-8b and TGF-beta3 were, at least in part, responsible for the Lhx expression in the maxillary process.

The premaxillary triangle: clue to the diagnosis of cleft lip and palate

OBJECTIVE

The prenatal detection rate of cleft lip and palate is low, especially in low-risk patients who undergo targeted sonography. The reason is that evaluating surface anatomy is relatively difficult and requires operator expertise. Our purpose was to describe a technique to improve the diagnostic accuracy of facial clefts (lip and palate) and to assess the feasibility of including this technique as part of standard protocol during targeted imaging.

METHODS

A prospective study was done during 2000 through 2002 to evaluate the accuracy of the "premaxillary triangle (PMT) sign": a new sign to diagnose unilateral cleft lip and palate in women referred for prenatal sonography at our center. Patients with only isolated unilateral cleft lip and palate and cleft lip were included in this study. Before this, all examiners were trained to image the PMT. The images were reviewed by a senior consultant. It was later decided to include this sign as part of the protocol of targeted sonography done between 18 and 22 weeks in our institution. However, depending on the fetal position, the PMT was documented even in patients referred for the first time in late second and third trimesters.

RESULTS

Twenty-nine cases of isolated facial clefts were diagnosed during the study period, of which 2 had unilateral cleft lip and 27 had unilateral cleft lip and palate. The PMT sign was absent in all cases of unilateral cleft lip and palate but was present in 2 cases of isolated cleft lip without cleft palate.

CONCLUSIONS

The PMT sign can be easily incorporated into targeted sonography at 18 to 22 weeks' gestation. Its inclusion would help in increasing the detection rate of unilateral cleft lip and palate. It may also be potentially used for differentiating between isolated cleft lip and cleft lip and palate, which helps in better prenatal counseling.

Comparative ontogeny and phylogeny of the upper jaw skeleton in amniotes

The morphology, position, and presence of the upper jaw bones vary greatly across amniote taxa. In this review, we compare the development and anatomy of upper jaw bones from the three living amniote groups: reptiles, birds, and mammals. The study of reptiles is particularly important as comparatively little is known about the embryogenesis of the jaw in this group. Our review covers the ontogeny and phylogeny of membranous bones in the face. The aim is to identify conserved embryonic processes that may exist among the three major amniote groups. Finally, we discuss how temporal and spatial regulation of preosseous condensations and ossification centers can lead to variation in the morphology of amniote upper jaw bones.

Study ofPax6 mutant rat revealed the association between upper incisor formation and midface formation

In this study, we investigated the process of supernumerary upper incisor formation in the Pax6 mutant rat, rSey(2)/rSey(2), which exhibits a facial cleft between the medial nasal and maxillary processes. Histological investigation and epithelial labeling studies of wild type rat embryos indicated that the upper incisor develops by fusion of two primary dental placodes (PDPs) in the medial nasal process with a contribution from the epithelium of the maxillary process. In the rSey(2)/rSey(2) embryo, both PDPs are formed but they stay apart, then subsequently these PDPs independently develop into upper incisor tooth buds. In order to examine if the failure of the two placodes to fuse is due to the cleft between the maxillary and medial nasal processes, maxillary and medial nasal process fusion was inhibited with a barrier in wild type embryos. This resulted in the maintenance of the two distinct PDPs. These results demonstrate that fusion of the facial processes reduces the number of odontogenic placodes and is required to assemble all components at one site for rat upper incisor formation. The results also provide further insight into the mechanism of supernumerary incisor formation in human cleft lip conditions.

First-trimester maternal serum level of pregnancy-associated plasma protein-A is an independent predictor of fetal maxillary bone length

OBJECTIVE

To derive a nomogram of fetal maxillary bone length (MAX) for a Chinese population and to study whether first-trimester maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) is an independent predictor of fetal MAX.

METHODS

This was a prospective observational study over 10 months examining Chinese women with a singleton pregnancy who attended the first-trimester screening program for Down syndrome. The subjects had the fetal crown-rump length (CRL), nuchal translucency, MAX, maternal serum PAPP-A and free beta-human chorionic gonadotropin (fbeta-hCG) levels measured. A nomogram of MAX was derived using normal pregnancies with reliable dates. The correlations between MAX, CRL, PAPP-A and fbeta-hCG levels were studied, after correction for gestational dependency using Z-score transformation for the ultrasound markers (Z-MAX and Z-CRL), and logarithmic transformation of multiple of gestation-specific medians for the biochemical markers (log10PAPP-A multiples of the median (MoM) and log10fbeta-hCG MoM), using the Pearson test and multiple regression analysis.

RESULTS

During the study period, 607 Chinese women met the inclusion criteria. The mean gestational age at the first-trimester screening was 12 + 4 weeks (SD, 4 days). Curve estimation analysis showed that a linear relationship fit best between MAX and CRL (MAX (mm) = -0.01 + 0.101 * CRL (mm); r = 0.826; P < 0.0001), and between MAX and gestational age (MAX (mm) = -8.465 + 0.170 * gestational age (day); r = 0.754; SD = 0.71; P < 0.0001). There were significant positive correlations between Z-MAX and Z-CRL (r = 0.627; P = < 0.0001), Z-MAX and log10PAPP-A MoM (r = 0.239; P = < 0.0001). Multiple regression analysis showed that both Z-CRL (P = < 0.0001) and log10 PAPP-A MoM (P = 0.048) were independent predictors for Z-MAX.

CONCLUSION

Both CRL and maternal levels of PAPP-A are independent predictors of the fetal MAX measured during the first trimester. The positive correlation between PAPP-A levels and fetal MAX is consistent with the known biological function of PAPP-A on bone growth. This association must be adjusted for when both PAPP-A and MAX are combined for screening of Down syndrome.

Nomogram of maxillary bone length in normal pregnancies

OBJECTIVE

The aim of this study was to define normal ultrasonographic growth of the fetal maxillary bone throughout pregnancy as a basis for further studies and as normative data for assessing deviations in growth.

METHODS

A prospective cross-sectional study was performed. Consecutive routine biometric measurements and fetal organ scans were obtained from patients undergoing elective fetal anatomic surveys. Special attention was paid to the profile view of the fetal face, and the maxillary bone was identified and measured.

RESULTS

Three hundred twenty-seven fetuses between 13 and 40 weeks' gestation were scanned. The maxillary bone is seen as a rodlike structure; it is a part of the facial skeleton that allows the opening and closing of the pharynx. A linear growth function was observed across gestational age (GA), and first-degree correlation was found to exist between GA and the maxillary bone (r = .645; P < .0001; y = 7.78 + 0.18 x GA). Significant correlation was also found between the maxillary bone and biparietal diameter (BPD) (r = 0.652; P > .0001; y = 8.36 + 0.66 x BPD), head circumference (HC) (r = .645; P < .0001; y = 8.39 + 0.18 x HC), femoral bone length (FBL) (r = .640; P < .0001; y = 9.28 + 0.7 x FBL), and abdominal circumference (AC) (r = .640; P < .0001; y = 8.91 + 0.17 x AC).

CONCLUSIONS

Normative data for ultrasonographic measurements of the fetal maxillary bone throughout pregnancy are provided. These data potentially allow the prenatal diagnosis of abnormal maxillary bone length.

Cross-talk between the TGFβ and Wnt signaling pathways in murine embryonic maxillary mesenchymal cells

The transforming growth factor beta (TGFbeta) and Wnt signaling pathways play central roles regulating embryogenesis and maintaining adult tissue homeostasis. TGFbeta mediates its cellular effects through types I and II cell surface receptors coupled to the nucleocytoplasmic Smad proteins. Wnt signals via binding to a cell surface receptor, Frizzled, which in turn activates intracellular Dishevelled, ultimately leading to stabilization and nuclear translocation of beta-catenin. Previous studies have demonstrated several points of cross-talk between the TGFbeta and Wnt signaling pathways. In yeast two-hybrid and GST-pull down assays, Dishevelled-1 and Smad 3 have been shown to physically interact through the C-terminal one-half of Dishevelled-1 and the MH2 domain of Smad 3. The current study demonstrates that co-treatment of murine embryonic maxillary mesenchyme (MEMM) cells with Wnt-3a and TGFbeta leads to enhanced reporter activity from TOPflash, a Wnt-responsive reporter plasmid. Transcriptional cooperation between TGFbeta and Wnt did not require the presence of a Smad binding element, nor did it occur when a TGFbeta-responsive reporter plasmid (p3TP-lux) was transfected. Overexpression of Smad 3 further enhanced the cooperation between Wnt and TGFbeta while overexpression of dominant-negative Smads 2 and 3 inhibited this effect. Co-stimulation with TGFbeta led to greater nuclear translocation of beta-catenin, providing explanation for the effect of TGFbeta on Wnt-3a reporter activity. Wnt-3a exerted antiproliferative activity in MEMM cells, similar to that exerted by TGFbeta. In addition, Wnt-3a and TGFbeta in combination led to synergistic decreases in MEMM cell proliferation. These data demonstrate a functional interaction between the TGFbeta and Wnt signaling pathways and suggest that Wnt activation of the canonical pathway is an important mediator of MEMM cell growth.

Short hard palate in prenatal trisomy 21

OBJECTIVE

The aim of the present study was for the first time to examine on postmortal material the total midpalatal length of the hard palate and the length of its two components (the maxillary and palatine parts) in trisomy 21 fetuses, and to compare the results to normal standards.

DESIGN

Material from 31 human fetuses with genetically verified trisomy 21 was studied. The fetuses were derived from legally induced or spontaneous abortions. Palates were, after sectioning, radiographed in lateral projection (Grenz Ray radiographic apparatus). Cephalometric measurements were performed with a digital caliper. Statistically, the length measurements for the two groups were compared, adjusting for crown rump length (CRL) through linear regression. At two specific ages (150 and 170 mm CRL), the length of the palatal components in trisomy 21 was compared to normal standards.

RESULTS

For CRL 150 mm and CRL 170 mm it appears that all three palatal lengths, total length, maxillary length, and palatinal length are significantly shorter in fetuses with trisomy 21.

CONCLUSION

The main conclusion of our study is that the total palatal length in prenatal trisomy 21 is shorter than normal and that this is due both to a shortness of the maxillary and the palatine components of the hard palate.

Interaction between Smad 3 and Dishevelled in murine embryonic craniofacial mesenchymal cells

OBJECTIVES

To determine the in vivo interaction between Smad 3 and Dishevelled-1.

DESIGN

Cell culture transfection followed by immunoprecipitation with specific antibodies.

SETTING AND SAMPLE POPULATION

The Department of Molecular, Cellular, and Craniofacial Biology, Birth Defects Center, University of Louisville.

EXPERIMENTAL VARIABLE

Overexpression of myc-Smad 3.

OUTCOME MEASURE

Western blotting of anti-Dishevelled immunoprecipitates for Smad 3.

RESULTS

Smad 3 and Dishevelled isoforms-1, -2, and -3 all bind Smad 3 in glutathione-S-transferase (GST) pull-down assays and Smad 3 binds to Dishevelled-1 in vivo. Stimulation of the transforming growth factor beta (TGFbeta) pathway leads to increased binding of Smad 3 and Dishevelled-1 in vivo.

CONCLUSION

Smad 3 binds all three known isoforms of Dishevelled and binds Dishevelled 1 in vivo. TGFbeta signaling modulates the interaction between Smad 3 and Dishevelled-1.