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.

Msx1 deficiency interacts with hypoxia and induces a morphogenetic regulation during mouse lip development

Nonsyndromic clefts of the lip and palate are common birth defects resulting from gene-gene and gene-environment interactions. Mutations in human MSX1 have been linked to orofacial clefting and we show here that Msx1 deficiency causes a growth defect of the medial nasal process (Mnp) in mouse embryos. Although this defect alone does not disrupt lip formation, Msx1-deficient embryos develop a cleft lip when the mother is transiently exposed to reduced oxygen levels or to phenytoin, a drug known to cause embryonic hypoxia. In the absence of interacting environmental factors, the Mnp growth defect caused by Msx1 deficiency is modified by a Pax9-dependent 'morphogenetic regulation', which modulates Mnp shape, rescues lip formation and involves a localized abrogation of Bmp4-mediated repression of Pax9 Analyses of GWAS data revealed a genome-wide significant association of a Gene Ontology morphogenesis term (including assigned roles for MSX1, MSX2, PAX9, BMP4 and GREM1) specifically for nonsyndromic cleft lip with cleft palate. Our data indicate that MSX1 mutations could increase the risk for cleft lip formation by interacting with an impaired morphogenetic regulation that adjusts Mnp shape, or through interactions that inhibit Mnp growth.

[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.

Face morphogenesis is promoted by Pbx-dependent EMT via regulation of Snail1 during frontonasal prominence fusion

Human cleft lip with or without cleft palate (CL/P) is a common craniofacial abnormality caused by impaired fusion of the facial prominences. We have previously reported that, in the mouse embryo, epithelial apoptosis mediates fusion at the seam where the prominences coalesce. Here, we show that apoptosis alone is not sufficient to remove the epithelial layers. We observed morphological changes in the seam epithelia, intermingling of cells of epithelial descent into the mesenchyme and molecular signatures of epithelial-mesenchymal transition (EMT). Utilizing mouse lines with cephalic epithelium-specific Pbx loss exhibiting CL/P, we demonstrate that these cellular behaviors are Pbx dependent, as is the transcriptional regulation of the EMT driver Snail1. Furthermore, in the embryo, the majority of epithelial cells expressing high levels of Snail1 do not undergo apoptosis. Pbx1 loss- and gain-of-function in a tractable epithelial culture system revealed that Pbx1 is both necessary and sufficient for EMT induction. This study establishes that Pbx-dependent EMT programs mediate murine upper lip/primary palate morphogenesis and fusion via regulation of Snail1. Of note, the EMT signatures observed in the embryo are mirrored in the epithelial culture system.

Systems biology of facial development: contributions of ectoderm and mesenchyme

The rapid increase in gene-centric biological knowledge coupled with analytic approaches for genomewide data integration provides an opportunity to develop systems-level understanding of facial development. Experimental analyses have demonstrated the importance of signaling between the surface ectoderm and the underlying mesenchyme are coordinating facial patterning. However, current transcriptome data from the developing vertebrate face is dominated by the mesenchymal component, and the contributions of the ectoderm are not easily identified. We have generated transcriptome datasets from critical periods of mouse face formation that enable gene expression to be analyzed with respect to time, prominence, and tissue layer. Notably, by separating the ectoderm and mesenchyme we considerably improved the sensitivity compared to data obtained from whole prominences, with more genes detected over a wider dynamic range. From these data we generated a detailed description of ectoderm-specific developmental programs, including pan-ectodermal programs, prominence- specific programs and their temporal dynamics. The genes and pathways represented in these programs provide mechanistic insights into several aspects of ectodermal development. We also used these data to identify co-expression modules specific to facial development. We then used 14 co-expression modules enriched for genes involved in orofacial clefts to make specific mechanistic predictions about genes involved in tongue specification, in nasal process patterning and in jaw development. Our multidimensional gene expression dataset is a unique resource for systems analysis of the developing face; our co-expression modules are a resource for predicting functions of poorly annotated genes, or for predicting roles for genes that have yet to be studied in the context of facial development; and our analytic approaches provide a paradigm for analysis of other complex developmental programs.

Nasolabial dimensions of the facial profile at 20 to 37 weeks' gestation on 2- and 3-dimensional sonography in normal Korean fetuses

OBJECTIVES

The purpose of this study was to evaluate normal nasolabial dimensions using the images of facial profiles in normal Korean fetuses.

METHODS

We conducted a cross-sectional study of 355 normal fetuses at 14 to 39 weeks' gestation. After the exclusion of inadequate images and inadequate numbers of fetuses at 14 to 19 and 37 to 39 weeks' gestation, the sonographic facial profiles from 222 fetuses at 20 to 37 weeks' gestation were evaluated. Five parameters, nose length, nose protrusion, pronasal-subnasal distance, distance between the upper philtrum and mouth, and distance between the tip of the nose and mouth, were measured and are presented according to gestational age. Data were analyzed by intraclass correlation coefficients and regression analysis.

RESULTS

There were significant linear correlations between gestational age and nose length (R = 0.390; P < .001), pronasal-subnasal distance (R = 0.415; P < .001), and distance between the upper philtrum and mouth (R = 0.315; P < .001). There were significant quadratic relationships between gestational age and nose protrusion (R(2) = 0.213; P < .001) and distance between the tip of the nose and mouth (R(2) = 0.173; P < .001).

CONCLUSIONS

We provide preliminary normative nasolabial dimensions of facial profiles at 20 to 37 weeks' gestation in normal Korean fetuses. These data may be of help not only in the understanding of normal nasolabial growth in utero but also in the diagnosis of abnormal facial dimensions.

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.

The golden ratio of nasal width to nasal bone length

PURPOSE

To calculate the ratio of fetal nasal width over nasal bone length at 14-39 weeks' gestation in Caucasian women.

METHODS

Fetal nasal bone length and nasal width at 14-39 weeks' gestation were measured in 532 normal fetuses. The mean and standard deviations of fetal nasal bone length, nasal width and their ratio to one another were calculated in normal fetuses according to the gestational age to establish normal values.

RESULTS

A positive and linear correlation was detected between the nasal bone length and the gestational week, as between the nasal width and the gestational week. No linear growth pattern was found between the gestational week and the ratio of nasal width to nasal bone length, nearly equal to phi, throughout gestation.

CONCLUSION

The ratio of nasal width to nasal bone length, approximately equal to phi, can be calculated at 14-38 weeks' gestation. This might be useful in evaluating fetal abnormalities.

Differential Shh, Bmp and Wnt gene expressions during craniofacial development in mice

In this study, Bmp-4, Wnt-5a and Shh gene expressions were compared during early craniofacial development in mice by comparative non-isotopic in situ hybridization. Wild-type C57BL/6J mice were studied at various stages of embryonic development (from 8.5- to 13.5-day-old embryos--E8.5-13.5). During early odontogenesis, transcripts for Bmp-4, Shh and Wnt-5a were co-localised at the tooth initiation stage. At E8.5, Shh mRNA expression was restricted to diencephalon and pharyngeal endoderm. Before maxillae and mandible ossification, Bmp-4 and Wnt-5a signals were detected in the mesenchymal cells and around Meckel's cartilage. During palatogenesis, Shh was expressed only in the epithelium and Wnt-5a only in the mesenchyme of the elevating palatal shelves. During tongue development, Shh expression was found in mesenchyme, probably contributing to tongue miogenesis, while Wnt-5a signal was in the epithelium, possibly during placode development and papillae formation. Taken together, these findings suggest that Bmp-4, Shh and Wnt-5a gene expressions may act together on the epithelial-mesenchymal interactions occurring in several aspects of the early mouse craniofacial development, such as odontogenesis, neuronal development, maxillae and mandible ossification, palatogenesis and tongue formation.

FREM1 mutations cause bifid nose, renal agenesis, and anorectal malformations syndrome

An autosomal-recessive syndrome of bifid nose and anorectal and renal anomalies (BNAR) was previously reported in a consanguineous Egyptian sibship. Here, we report the results of linkage analysis, on this family and on two other families with a similar phenotype, which identified a shared region of homozygosity on chromosome 9p22.2-p23. Candidate-gene analysis revealed homozygous frameshift and missense mutations in FREM1, which encodes an extracellular matrix component of basement membranes. In situ hybridization experiments demonstrated gene expression of Frem1 in the midline of E11.5 mouse embryos, in agreement with the observed cleft nose phenotype of our patients. FREM1 is part of a ternary complex that includes FRAS1 and FREM2, and mutations of the latter two genes have been reported to cause Fraser syndrome in mice and humans. The phenotypic variability previously reported for different Frem1 mouse mutants suggests that the apparently distinct phenotype of BNAR in humans may represent a previously unrecognized variant of Fraser syndrome.

[Reproducibility of the fetal nasal bone measurement by means of bidimensional and three-dimensional ecography during the second trimester of the pregnancy]

AIMS

The utility of the valuation-measurement of the nasal bone in the prognosis of chromosomopaties during the second trimester of the pregnancy is demonstrated.

OBJECTIVE

To evaluate the repeatability of nasal bone measurement during second trimester with bidimensional and three-dimensional sonography.

MATERIAL AND METHOD

Nasal bone was measured in 50 single pregnancies. First observer carried out two measures of nasal bone with bidimensional sonography, and 1 measure with three-dimensional sonography. Second observer carried out just one measure with bidimensional sonography (2D) and just another one with three-dimensional sonography (3D). We studied the intraobserver variability with 2D sonography, and the interobserver variability with 2D and 3D sonography.

RESULTS

2D-sonography: nasal bone measurement showed excellent intraobserver correlation with a correlation coefficient of 0,87 (CI 95%: 0,78-0,93) and a little means difference of 0,18 (SD: 0,74). Indeed, there was a good interobserver correlation with a correlation coefficient of 0,92 (CI 95%: 0,85-0,95), and a means difference of 0,14 (SD: 0,56). 3D-sonography: there was a acceptable interobserver correlation with correlation coefficient of 0,70 (CI 95%: 0,52-0,82).

CONCLUSION

Nasal bone measurement is highly reproducible by means of bidimensional sonography while using three-dimensional sonography, the results are just acceptable.

Management of bilateral cleft lip and nasal deformity

PURPOSE OF REVIEW

Management of bilateral cleft lip and nasal deformity can be a challenging task. This paper provides an overview of bilateral cleft lip and nasal deformity with an updated review of current management issues in the literature.

RECENT FINDINGS

The Centers for Disease Control and Prevention recently reported that orofacial clefts are now the most common birth defect. While this statistic may be disheartening, the increased prevalence brings the problem to light at the forefront of the medical community, thus gaining more support and resources. Many techniques have been described for repair of bilateral cleft lip and nasal deformity. A recent advancement in presurgical orthopedics is the use of nasoalveolar molding to narrow wide clefts.

SUMMARY

Surgical management of bilateral cleft lip and nasal deformity poses a challenge to the skill and judgment of the cleft surgeon. Although techniques continue to evolve over the decades, the basic principles of cleft surgery remain the same. The main principles are to achieve an appropriate philtral size and shape, to position the cartilages in a more optimal position, and to attain muscular continuity and symmetry for optimal appearance and function. Thus, while keeping the basic principles in mind, management of bilateral cleft lip and nasal deformity becomes a valuable and rewarding experience for the surgeon, patient and caregiver.

Temporal migration of gonadotrophin-releasing hormone-1 neurones is modified in GAD67 knockout mice

Gonadotrophin-releasing hormone (GnRH-1) neurones reside in the forebrain and regulate gonadal function via the hypothalamic-pituitary-gonadal axis. Disruption of this axis results in reproductive dysfunction. During embryonic development, GnRH-1 neurones migrate from the nasal pit through the nasal/forebrain junction (NFJ) into the developing brain. Prenatally gamma-aminobutyric acid (GABA) is excitatory and has been shown to play a role in nervous system development. Both in vivo and in vitro experiments suggest that GABA inhibits migration of GnRH-1 neurones. The present study examines the migration of GnRH-1 neurones in GAD67 knockout (KO) mice to further elucidate the role of GABA on GnRH-1 neuronal development. Three stages were examined, embryonic day (E)12.5, E14.5 and E17.5. GnRH-1 cell number and location were analysed by immunocytochemistry and in situ hybridisation histochemistry. The total number of GnRH-1 immunopositive cells was similar between wild-type (WT) and KO mice. However, significant differences were found in the overall distribution of GnRH-1 immunopositive cells in GAD67 KO compared to WT mice at all stages. Subsequent analysis by area revealed differences occurred at the NFJ with an increase in GnRH-1 cells in GAD67 KO at E14.5 and a decrease in GnRH-1 cells in GAD67 KO at E17.5. Comparable counts for cells expressing GnRH-1 transcript and protein were obtained. These data indicate that attenuated levels of GABA accelerate GnRH-1 cell migration in nasal areas as well as movement of GnRH-1 cells into the central nervous system at the NFJ.

Laser burn wound healing in naso-labial region of fetal and neonatal mice

OBJECTIVE

To investigate the characteristics of wound healing in the mouse naso-labial region in both the fetal and neonatal stages, histological and immunohistochemical analyses were performed using a newly established laser burn wound healing system.

MATERIALS AND METHODS

Fetal mice at embryonic day 14 (E 14) were wounded as a model of fetal wound healing. To compare it, neonatal mice at day 5 after birth (d 5) were adopted as a model of neonatal wound healing. The healing process was examined by van Gieson staining and immunohistochemistry for fibronectin and tenascin.

RESULTS

Relatively large damage remained after wound healing even in fetal mice. In both types of wound healing, rapid regeneration of muscle tissues were observed. Fibronectin and tenascin immunostaining was detected not only in wound healing region, but also in the endomysium of regenerating muscle tissues. Especially, tenascin showed a restricted expression pattern.

CONCLUSIONS

Rapid regeneration of muscle tissues in the naso-labial region in both the fetal and neonatal mice seemed to leave relatively large damage even in the fetal wound healing. Contracted force exerted by muscle tissues may be a reason for this phenomenon. Fibronectin and tenascin were closely related to the wound healing process including muscle regeneration in this region.

Terminal nerve in the mouse-eared bat (Myotis myotis): ontogenetic aspects

As in other mammals, ontogenesis of the terminal nerve (TN) in the mouse-eared bat (Myotis myotis) starts shortly after the formation of the olfactory placode, a derivative of the ectoderm. During development of the olfactory pit, proliferating neuroblasts thicken the placodal epithelium and one cell population migrates toward the rostroventral tip of the telencephalon. Here they accumulate in a primordial terminal ganglion, which successively divides into smaller units. Initial fibers of the TN can be distinguished from olfactory fibers in the mid-embryonic period. The main TN fiber bundle (mfb) originates from the anteriormost ganglion in the nasal roof, whereas one or more inconstant smaller fiber bundles (sfb) originate from one or more smaller ganglia in the basal part of the rostral nasal septum. The fibers of the mfb and sfbs join in the posterior quarter of the nasal roof before reaching the central ganglion (M) located in the meninges medial to the olfactory bulb. From the mid-fetal period onward, a thin TN fiber bundle with some intermingled perikarya connects M to the brain by penetrating its wall rostral to the olfactory tubercle. Additional smaller ganglia may occur in this region. The TN and its ganglia persist in postnatal and adult bats but the number of perikarya is reduced here. Moreover, the different potential functions of the TN are discussed briefly.

Sox2 and Pou2f1 interact to control lens and olfactory placode development

Sox2, which encodes an SRY-like HMG box transcription factor, is critical for vertebrate development. Sox2 mediates its transcriptional effects through the formation of complexes with specific co-factors, many of which are unknown. In this report, we identify Oct-1, encoded by the Pou2f1 gene, as a co-factor for Sox2 in the context of mouse lens and nasal placode induction. Oct-1, Sox2, and Pax6 are co-expressed during lens and nasal placode induction and during subsequent developmental stages. Genetic combination of Sox2 and Pou2f1 mutant alleles results in impaired induction of the lens placode, an ocular phenotype that includes anophthalmia, and a complete failure of nasal placode induction. These ocular and nasal phenotypes closely resemble those observed in Pax6 null embryos. Moreover, we identify DNA-binding sites that support the cooperative formation of a complex between Sox2 and Oct-1 and mediate Sox2/Oct-1-dependent transactivation of the Pax6 lens ectoderm enhancer in vitro. We demonstrate that the same Sox- and Octamer-binding sites are essential for Pax6 enhancer activity in the lens placode and its derivatives in transgenic mouse embryos. Collectively, these results indicate that Pou2f1, Sox2 and Pax6 are interdependent components of a molecular pathway utilized in both lens and nasal placode induction.

Cardiovascular and craniofacial defects in Crk-null mice

The Crk adaptor protein, which is encoded by two splice variants termed CrkI and CrkII, contains both SH2 and SH3 domains but no catalytic region. It is thought to function in signal transduction processes involved in growth regulation, cell transformation, cell migration, and cell adhesion. Although the function of Crk has been studied in considerable detail in cell culture, its biological role in vivo is still unclear, and no Crk-knockout mouse model has been available. Therefore, we generated a complete null allele of Crk in mice by using the Cre-loxP recombination approach. The majority of Crk-null mice die at late stages of embryonic development, and the remainder succumb shortly after birth. Embryos lacking both CrkI and CrkII exhibited edema, hemorrhage, and cardiac defects. Immunohistochemical examination suggested that defects in vascular smooth muscle caused dilation and rupturing of blood vessels. Problems in nasal development and cleft palate were also observed. These data indicate that Crk is involved in cardiac and craniofacial development and that it plays an essential role in maintaining vascular integrity during embryonic development.

Second trimester ultrasound prenasal thickness combined with nasal bone length: a new method of Down syndrome screening

OBJECTIVE

To evaluate ultrasound prenasal thickness (PT) as a way of enhancing the Down syndrome (DS) screening performance of second-trimester nasal bone (NB) length measurement.

METHODS

Twenty-one DS and 500 normal fetuses were scanned at 14-27 weeks' gestation. The affected karyotype was known to the person performing the scan. Both PT and NB were measured in a mid-sagittal position and results were expressed in multiples of the normal gestation-specific median (MoM). Gaussian modelling was used to predict the performance of routine screening.

RESULTS

Among DS fetuses, the PT median was 1.35 MoM, a highly statistically significant increase compared with the unaffected pregnancies (p < 0.0001, Wilcoxon Rank Sum Test, two-tailed). The NB median was 0.87 MoM (p < 0.0005) and the ratio PT/NB median was 1.51 MoM (p < 0.0001). In the normal fetuses, the two markers were positively correlated (0.25, p < 0.0001), whereas in the DS fetuses there was a non-significant negative correlation (-0.24, p = 0.33). For a 5% false-positive rate, the model predicted detection rate was 70% for PT and NB compared with 43% for NB alone.

CONCLUSION

In the second trimester, PT is increased on average in DS fetuses. Combining PT and NB measurement could yield a higher screening detection rate than NB alone. Confirmation of our findings in a series of women scanned before the karyotype was known is needed before the method can be clinically implemented.

Noses and neurons: induction, morphogenesis, and neuronal differentiation in the peripheral olfactory pathway

Non-axial mesenchymal/epithelial (M/E) induction guides peripheral olfactory pathway differentiation using cellular and molecular mechanisms similar to those in the developing limbs, aortic arches, and branchial arches. At each of these bilaterally symmetric sites off the midline axis, a thickened ectodermal epithelium is apposed to a specialized mesenchyme derived largely, but not exclusively, from the neural crest. The capacity of M/E interaction in the olfactory primordia (the combined olfactory placodal epithelium and adjacent mesenchyme) to induce a distinct class of sensory receptor neurons-olfactory receptor neurons-suggests that this mechanism has been modified to accommodate neurogenesis, neurite outgrowth, and axon guidance, in addition to musculoskeletal differentiation, chondrogenesis, and vasculogenesis. Accordingly, although the olfactory primordia share signaling molecules and transcriptional regulators with other bilaterally symmetric, non-axial sites such as limb buds, their activity may be adapted to mediate distinct aspects of cellular differentiation and process outgrowth during the initial assembly of a sensory pathway-the primary olfactory pathway-during early forebrain development.

Pax6-dependence of Six3, Eya1 and Dach1 expression during lens and nasal placode induction

The Drosophila eyeless gene plays a central role in fly eye development and controls a subordinate regulatory network consisting of the so, eya and dac genes. All three genes have highly conserved mammalian homologs, suggesting possible conservation of this eye forming regulatory network. sine oculis (so) belongs to the so/Six gene family, and Six3 is prominently expressed in the developing mammalian eye. Eya1 and Dach1 are mammalian homologs of eya and dac, respectively, and although neither Eya1 nor Dach1 knockout mice express prenatal eye defects, possibilities exist for postnatal ocular phenotypes or for functional redundancy between related family members. To examine whether expression relationships analogous to those between ey, so, eya and dac exist in early mammalian oculogenesis, we investigated Pax6, Six3, Eya1 and Dach1 protein expression in murine lens and nasal placode development. Six3 expression in the pre-placode lens ectoderm is initially Pax6-independent, but subsequently both its expression and nuclear localization become Pax6-dependent. Six3, Dach1 and Eya1 nasal expression in pre-placode ectoderm are also initially Pax6-independent, but thereafter become Pax6-dependent. Pax6, Six3, Dach1 and Eya1 are all co-expressed in the developing ciliary marginal zone, a source of retinal stem cells in some vertebrates. An in vitro protein-protein interaction is detected between Six3 and Eya1. Collectively, these findings suggest that the Pax-Eya-Six-Dach network is at best only partly conserved during lens and nasal placode development. However, the findings do not rule out the possibility that such a regulatory network acts at later stages of oculogenesis.

Overlapping expression patterns of the multiligand endocytic receptors cubilin and megalin in the CNS, sensory organs and developing epithelia of the rodent embryo

Cubilin and megalin are multiligand epithelial endocytic receptors well characterized in the adult kidney and ileum where they form a complex essential for protein, lipid and vitamin uptake. Although inactivation of the megalin gene leads to holoprosencephaly and administration of anti-cubilin antibodies induces fetal resorptions or cranio-facial malformations their function in the developing embryo remains unclear. We recently showed that both proteins are strongly expressed by the maternal-fetal interfaces and the neuroepithelium of the early rodent embryo where they co-localize and form a complex important for nutrient uptake. The aim of the present study was the further investigation of cubilin expression at later developmental stages of the rodent embryo and its correlation to that of megalin. Immunohistochemical and in situ hybridization analysis showed striking similarities in the spatial and temporal expression patterns of cubilin and megalin. The electrophoretic mobility of both proteins was identical to that of the adult as revealed by Western blot analysis. Cubilin and megalin were strongly expressed in the sensory organs, the central nervous system, the respiratory and urogenital tracts as well as in the thymus, parathyroids and thyroid. In each site, the expression mainly concerned epithelial structures and correlated with the onset of epithelial induction. Depending on the site, a decreased or restricted expression was observed by the end of the gestation for both proteins.

Embryonic staging system for the short-tailed fruit bat,Carollia perspicillata, a model organism for the mammalian orderChiroptera, based upon timed pregnancies in captive-bred animals

There are approximately 4,800 extant species of mammals that exhibit tremendous morphological, physiological, and developmental diversity. Yet embryonic development has been studied in only a few mammalian species. Among mammals, bats are second only to rodents with regard to species number and habitat range and are the most abundant mammals in undisturbed tropical regions. Bat development, though, remains relatively unstudied. Here, we describe and illustrate a staging series of embryonic development for the short-tailed fruit bat, Carollia perspicillata, based on embryos collected at timed intervals after captive matings. As Carollia can be readily maintained and propagated in captivity and is extremely abundant in the wild, it offers an attractive choice as a chiropteran model organism. This staging system provides a framework for studying Carollia embryogenesis and should prove useful as a guide for embryological studies of other bat species and for comparisons with other orders of mammals.

Cleft lip nose: a different approach

The aim of this study is to demonstrate a different manner of treating cleft lip nose by approaching the problem at its origin, the nasolabial gap. The surgical technique we propose corrects the affected structures from the "bottom to the top." First we have to make sure that the orbicularis oris is well oriented, then we have to create space for the twisted alar cartilage, and finally we reach the tip of the nose with less asymmetry to correct, compared with previously published data. Before attempting any additions of grafts, implants, etc. for the restoration of any congenital deformity, especially clefts, the surgical team must try to reposition, reorganize, and reorient the structures affected by a lack of continuity or a gap as a result of the embryogenesis.

Upper beak truncation in chicken embryos with the cleft primary palate mutation is due to an epithelial defect in the frontonasal mass

In this study, we used the chicken mutant strain known as cleft primary palate (cpp) to study the mechanisms of beak outgrowth. cpp mutants have complete truncation of the upper beak with normal development of the lower beak. Based on structural analysis and grafts of facial prominences, we localized the defect to the frontonasal mass and its derivatives. Several explanations that would account for the outgrowth defect were investigated, including abnormal expression of genes in the frontonasal epithelium, intrinsic defects in epithelium and/or mesenchyme defects in epithelial-mesenchymal signalling, a localized decrease in cell proliferation or a localized increase in programmed cell death. One of the genes expressed in the frontonasal epithelial growth zone, Fgf8, failed to down-regulate and was maintained for at least 48 hr beyond the time when down-regulation normally occurs. Recombination experiments further illustrated that the frontonasal mass epithelium was abnormal in the cpp mutants, whereas mutant mesenchyme was capable of normal outgrowth when combined with wild-type epithelium. Cell proliferation was not decreased in mutant embryos nor was cell death initially increased. Later, at stages 31-32, when the prenasal cartilage begins directed outgrowth, there was an increase in cell death within the mutant upper but not lower beak cartilage. The cpp beak truncation, therefore, is due to an epithelial defect in the frontonasal mass that is coincident with a failure to down-regulate expression of Fgf8.

[Ontogeny of the jaw]

Four pairs of branchial arch appear apparently in the neck region of human embryo about 32 days after fertilization. Maxillary prominence of the first branchial arch gives rise to the maxilla and zygomatic bone etc., and mandibular prominence forms the mandible and so on. Muscles for mastication are also derived from 1st branchial arch, into which fifth cranial nerves grow from the brain. Thus, human embryo improves the 1st branchial arches into the upper and lower jaws, and forms digestive organs needed for intake, mastication, and swallowing of foods. Finally they develop the brain for integral treatment of sensory information from eyes, tongue, nose, and ears.

Live view of gonadotropin-releasing hormone containing neuron migration

Neurons that synthesize GnRH control the reproductive axis and migrate over long distances and through different environments during development. Prior studies provided strong clues for the types of molecules encountered and movements expected along the migratory route. However, our studies provide the first real-time views of the behavior of GnRH neurons in the context of an in vitro preparation that maintains conditions comparable to those in vivo. The live views provide direct evidence of the changing behavior of GnRH neurons in their different environments, showing that GnRH neurons move with greater frequency and with more changes in direction after they enter the brain. Perturbations of guiding fibers distal to moving GnRH neurons in the nasal compartment influenced movement without detectable changes in the fibers in the immediate vicinity of moving GnRH neurons. This suggests that the use of fibers by GnRH neurons for guidance may entail selective signaling in addition to mechanical guidance. These studies establish a model to evaluate the influences of specific molecules that are important for their migration.

Early development of the nose in human embryos: a stereomicroscopic and histologic analysis

OBJECTIVES/HYPOTHESIS

To analyze the morphologic features of the nose in the human embryo from the 4th to 8th developmental week according to Carnegie stage.

STUDY DESIGN

Stereomicroscopic and histologic analysis of the morphology of the human embryo.

METHODS

A total of 27 cases of embryos, ranging from Carnegie stage 13 to 23, were analyzed. The external morphology was observed with a stereomicroscope, photographed, and analyzed. The histologic features were observed with a light microscope in the horizontally transected specimens stained with hematoxylin-eosin.

RESULTS

The nasal placode was observed in stage 13, and it became flat or even concave in stage 14. In stage 15, the nasal pit was formed. In stage 16, the nasal sac and nasal fin were observed. In stage 17, the oronasal membrane was formed by thinning of the nasal fin. In stage 18, the primitive choana was established by a rupture of the oronasal membrane. In stage 19, the lateral palatine process projected vertically below the level of the tongue. The cartilaginous nasal capsule was formed in stage 20. In stage 21, the olfactory area was localized to the upper portion of the lateral nasal wall and the nasal septum. In stage 22, the lateral palatine process developed in a somewhat horizontal orientation. In stage 23, the premaxilla and primitive choana were formed.

CONCLUSIONS

The development of the nose is most active from Carnegie stage 13 to 19, which corresponds to the end of the fourth embryonic week to the end of the seventh week. Thus, this period is considered to be the most important period in human nasal embryonic development.

Functional matrix cleft repair: principles and techniques

As an application of developmental anatomy, functional matrix cleft repair has scientific value. It tests out many aspects of periosteal physiology, and it is based squarely on concepts central to orthodontics. The "molecular revolution" has melded together developmental anatomy and genetics to create a new and clinically relevant model of facial development. This article outlines the scientific rationale for cleft repair based on this model.

Nasal capsular cartilage is required for rat transpalatal suture morphogenesis

In the cranial vault, suture morphogenesis occurs when the growing cranial bones approximate and overlap or abut one another. Patency of developing sutures is regulated by the underlying dura mater. Once cranial sutures form, bone growth proceeds from the sutures in response to growth signals from the rapidly expanding neurocranium. Facial sutures do not develop in contact with the dura mater. It was therefore hypothesized that facial suture morphogenesis and bone growth from facial sutures are regulated by tissues with an equivalent role to the dura mater. The present study was designed to test this hypothesis by characterizing the morphology and growth factor expression in developing transpalatal (TP) sutures and their surrounding tissues, and then assessing the role of the overlying nasal capsular (NC) cartilages in maintaining suture patency. TP sutures develop as overlapping sutures, similar to cranial coronal sutures, and expression of Tgf-betas in TP sutures was similar to their distribution in cranial coronal sutures. To establish whether NC cartilages play a role in regulating TP suture morphogenesis, fetal rat TP sutures were cultured with associated attached NC cartilages or with NC cartilages removed. Sutures cultured for upward of 5 days with intact NC cartilages remained patent and maintained their cellular and fibrous components. However, in the absence of NC cartilages, the cellular nature of the sutures was not maintained and they became progressively acellular, with bony bridging across the suture. This finding is similar to that for cranial vault sutures cultured in the absence of dura mater, indicating that NC cartilages play an equivalent role to dura mater in maintaining the patency of developing sutures. These studies indicate that tissue interactions likely regulate morphogenesis of all cranial and facial sutures.

Proboscis lateralis: a report of two cases

Proboscis Lateralis (PL) is one of the congenital anomalies of the nose which presents as obvious deformity. This is a report of two cases of the rare anomaly PL. One presented with right PL and the second presented with left PL. In this rare anomaly, the nasal cavity on one side is completely normal while on the affected side, the nasal cavity is replaced by a tube of skin and soft tissue attached to the inner canthus of the eye. This anomaly occurs sporadic as an isolated defect or in association with other anomalies. It is usually associated with failure of the paranasal sinuses and the nasolacrimal duct development. Embryologically, this anomaly is a result of imperfect fusion of the lateral nasal wall and maxillary processes (Int. J. Pediatr. Otorhinolaryngol. 23 (1992) 275).

Congenital nasal anomalies: a classification scheme

The purpose of this work was to develop a simple yet comprehensive classification scheme dedicated to congenital nasal anomalies. To date, no such classification system has been proposed and widely used. A 22-year retrospective review was performed. Two hundred sixty-one patients with congenital nasal anomalies were identified. From this extensive database, a systematic morphogenic classification system was devised. Congenital nasal deformities were classified into four categories. Type I, hypoplasia and atrophy, represents paucity, atrophy, or underdevelopments of skin, subcutaneous tissue, muscle, cartilage, and/or bone. Type II, hyperplasia and duplications, representing anomalies of excess tissue, ranging from duplications of parts to complete multiples, are categorized here. In the type III category, clefts, the comprehensive and widely utilized Tessier classification of craniofacial clefts is applied. Type IV deformities consist of neoplasms and vascular anomalies. Both benign and malignant neoplasms are found in this category.

Six1controls patterning of the mouse otic vesicle

Six1 is a member of the Six family homeobox genes, which function as components of the Pax-Six-Eya-Dach gene network to control organ development. Six1 is expressed in otic vesicles, nasal epithelia,branchial arches/pouches, nephrogenic cords, somites and a limited set of ganglia. In this study, we established Six1-deficient mice and found that development of the inner ear, nose, thymus, kidney and skeletal muscle was severely affected. Six1-deficient embryos were devoid of inner ear structures, including cochlea and vestibule, while their endolymphatic sac was enlarged. The inner ear anomaly began at around E10.5 and Six1was expressed in the ventral region of the otic vesicle in the wild-type embryos at this stage. In the otic vesicle of Six1-deficient embryos,expressions of Otx1, Otx2, Lfng and Fgf3,which were expressed ventrally in the wild-type otic vesicles, were abolished,while the expression domains of Dlx5, Hmx3, Dach1and Dach2, which were expressed dorsally in the wild-type otic vesicles, expanded ventrally. Our results indicate that Six1functions as a key regulator of otic vesicle patterning at early embryogenesis and controls the expression domains of downstream otic genes responsible for respective inner ear structures. In addition, cell proliferation was reduced and apoptotic cell death was enhanced in the ventral region of the otic vesicle, suggesting the involvement of Six1 in cell proliferation and survival. In spite of the similarity of otic phenotypes of Six1- and Shh-deficient mice, expressions of Six1 and Shhwere mutually independent.

The prenatal development of the human cerebellar field in Down syndrome

OBJECTIVES

To describe the development of the osseous field enclosing the cerebellum and part of the brain stem (the neuro-osteological cerebellar field) in Down syndrome, and compare the development with normal developmental standard of the field.

DESIGN

Radiographic, cephalometric and histologic examination of 58 legally or spontaneously aborted Down syndrome prenatal human fetuses; crown-rump length of 80-255 mm and approximate gestational age from 13 to 26 weeks.

RESULTS

The growth of the Down syndrome cerebellar field is smaller in the sagittal and vertical directions than in normal fetuses.

CONCLUSION

In the present study the pathological development of the cerebellar field was described in a genotypic sample. In combining normal and pathological development of neural and osseous tissues a better understanding of the genotype/phenotype interactions is attainable and fields of common gene expression maybe defined.

Developmental distribution of coxsackie virus and adenovirus receptor localized in the nervous system

Mouse coxsackie virus and adenovirus receptor (mCAR), which was isolated from the nerve growth cone-enriched fraction of newborn mouse brains, is a member of immunoglobulin-super family, and functions as a homophilic adhesion molecule. We observed the expression of mCAR in embryos to adult tissues by means of immunohistochemical analysis with a peptide antibody. mCAR expression was first detected in the embryonic ectoderm in the uterus on embryonic day 6.5 (E6.5). Then it was strongly expressed in the neuroepithelium of the neural tube, the developing brain and the spinal cord from E8.5 to postnatal day 7 (P7), in the cranial motor nerves from E9.5 to E11.5, and in the optic nerve from E13.5 to P7, which agrees with periods of their respective morphogenetic peaks. This expression of mCAR decreased postnatally and was absent in adult tissues. We found that mCAR occurred in a few proliferating cells of the hippocampal dentate gyrus, the subventricular zone (SVZ) of the lateral ventricles, and the rostral migratory stream (RMS) over P21. These observations demonstrate that mCAR was expressed characteristically in the immature neuroepithelium including progenitor cells or radial cells derived from the neural tube and in immature cells in a selected germinal zone of the mature brain. Based on our findings, we propose that mCAR is involved in migration and fasciculation during a restricted period as an adhesion molecule.

Ultrastructural characterization of the mesenchyme of the facial processes during development of the rat intermaxillary segment

This study quantifies ultrastructural changes within the mesenchyme of the maxillary and medial/lateral nasal processes before and after formation of the intermaxillary segment. At both day 11 and day 13 of development, 4 fetal rat heads were fixed with 3% glutaraldehyde and processed for electron microscopy. Differences between cells within the facial processes were discerned at day 11 of gestation. Significantly more rough endoplasmic reticulum was present in the cells of the maxillary processes than in the lateral nasal processes (p < .05), and a greater number of cell projections was found in the maxillary processes than in the medial nasal processes (p < .05). At day 13, no significant differences were found in the facial processes. Of particular note, a consistent increase in the number of cell projections within all the facial processes was found on day 13 when compared with day 11 (p < .05). This change may be related to intercellular signaling between the mesenchymal cells at the time of onset of major histogenic changes.

Functional analysis of chicken Sox2 enhancers highlights an array of diverse regulatory elements that are conserved in mammals

Sox2 expression marks neural and sensory primordia at various stages of development. A 50 kb genomic region of chicken Sox2 was isolated and scanned for enhancer activity utilizing embryo electroporation, resulting in identification of a battery of enhancers. Although Sox2 expression in the early embryonic CNS appears uniform, it is actually pieced together by five separate enhancers with distinct spatio-temporal specificities, including the one activated by the neural induction signals emanating from Hensen's node. Enhancers for Sox2 expression in the lens and nasal/otic placodes and in the neural crest were also determined. These functionally identified Sox2 enhancers exactly correspond to the extragenic sequence blocks conspicuously conserved between chicken and mammals, which are not discernible by sequence comparison among mammals.

Frontonasal dysplasia in 3H1 Br/Br mice

The adult Brachyrrhine (3H1 Br/+) mouse displays severe midfacial retrognathia, with a "pugnose" external appearance, but information concerning craniofacial morphology of the homozygote (3H1 Br/Br) mutant is lacking. This study characterized craniofacial phenotype and genotypic features of the homozygous condition. Segregation analysis was performed by phenotypic scoring of offspring from 3H1 Br/+ reciprocal matings. Whole-mount staining was undertaken to determine the presence or absence of cranial base structures in newborn and adult mice, while features of cranial base chondrification were examined using light microscopy and type II collagen immunohistochemistry. Karyotype analysis was performed to determine whether gross chromosomal aberrations were present. Finally, microsatellite mapping analysis was undertaken to provide further resolution of the Br locus. Results showed that Br was inherited as an autosomal semidominant feature. 3H1 Br/Br mice consistently lacked a presphenoid (with its lateral projections, including a preoptic root, postoptic root, and lesser wing). Karyotyping did not reveal major gross aberrations; however, microsatellite analysis localized Br to distal mouse chromosome 17 in the vicinity of D17Mit155. These results indicated that 3H1 Br/Br mice show characteristic features of frontonasal dysplasia, including median facial clefting and bifid cranium, as well sphenoidal malformations. Furthermore, this mutant should serve as a useful model for examining mechanisms of frontonasal dysplasia.

Recent developments in orofacial cleft genetics

Nonsyndromic cleft of the lip and/or palate (CLP or orofacial cleft) derives from an embryopathy with consequent failure of the nasal process and/or palatal shelves fusion. This severe birth defect is one of the most common malformations among live births. Nonsyndromic CLP is composed of two separate entities: cleft lip and palate (CL+/-P) and cleft palate only (CPO). Both have a genetic background, and environmental factors probably disclose these malformations. In CL+/-P, several loci have been identified, and, in one case, a specific gene has also been found. In CPO, one gene has been identified, but many more are probably involved. Because of the complexity of the genetics of nonsyndromic CLP as a result of the difference between CL+/-P and CPO, heterogeneity of each group caused by the number of involved genes, type of inheritance, and interaction with environmental factors, we discuss the more sound results obtained with different approaches: epidemiological studies, animal models, human genetic studies, and in vitro studies.

Chondrogenic differentiation during midfacial development in the mouse: in vivo and in vitro studies

Because the mouse is now the main model for developmental research of all types, it is important to understand the basic developmental pattern of various organs. The first aim of the present study was to establish normal prenatal developmental standards of the cartilaginous nasal capsule during embryonic development of the mouse. For this purpose we have performed sagittal and coronal sections ranging from E12.5 to E18.5 in gestation age. The primordia of the nasal septal cartilage is recognizable around the 14th embryonic day as demonstrated by the metachromatic toluidine blue staining and by immunostaining of type II collagen. Northern blot analysis of the transcription factors Cart-1 and Sox-9 indicated maximum mRNA levels at E12.5 then a decreased expression during the following days of gestation. Type II collagen and aggrecan mRNA levels are constant during the embryonic period. In the second part of this study, we have established a primary culture system where chondrocytes were isolated from E.18 mouse embryo nasal septum. The purpose of this second part was to assess if chondrocytes could further differentiate in vitro until the hypertrophic phase and matrix mineralization. After the condensation phase, the cells synthesize an extracellular matrix including type II collagen and aggrecan. Progressively, typical cartilaginous nodules composed of clusters of round cells are visible, then increase in size and finally mineralize at day 12 of culture. Cart-1 and Sox-9 mRNA levels remain constant throughout the cultures, whereas type II collagen and aggrecan gradually decrease. Ultrastructural observations of the nodules show typical chondrocytes embedded in a dense network of fibers with matrix vesicles and mineralized foci. Other ultrathin sections revealed the presence of chondrons, typical of hyaline cartilage. Results from this study provide useful tools to further investigate morphogenesis and differentiation of the cartilaginous nasal capsule, and could in the future serve as a basic developmental standard.

Microvascularization of the mucocutaneous junctions of the head in fetuses and neonates

The mucocutaneous junctions of the head (oral, nasal and palpebral) are transitional zones between the integuments and the mucosa. Their microvascularization is studied in the heads of fetuses and neonates by injection of agarized China ink into the vascular system. These zones are situated deep with respect to the free edge of the oral or nasal cavity or relative to the free margin of the eyelid. They present cutaneous-type microvascularization with a papillary network and reticular networks. Long capillary loops connected to the deep reticular network are their main feature. In the lips and eyelids, the morphology of the networks and their relationship with the orbicular muscles are suggestive of a functional structure.

Repair of the unilateral cleft lip/nose deformity

Successful surgical repair of the unilateral cleft lip and nose deformity, defined as normal orbicularis oris function and near-perfect symmetry of the repaired lip and nose, demands that the surgeon possess complete understanding of the embryology and anatomy of the midfacial defects. The surgical approach to repair of the unilateral cleft lip/nose should place great emphasis on achieving symmetry, not only with the lip segments but also perhaps even more importantly with the nasal tip. The reconstruction should recreate an intact fully functional orbicularis oris muscle across the cleft and camouflage the scar optimally. We have found that modification of the Millard rotation-advancement flap technique, with particular attention to the primary nasal repair, provides the best outcomes. In patients who have undergone primary repair of the lip and/or nose deformity, secondary rhinoplasty is generally required, regardless of the technique used at the primary repair. The degree of nasal deformity, however, is less severe following primary repair of the asymmetric nasal tip. We have found that the sliding flap cheliorhinoplasty, Wang's modification of the Vissarionov technique, provides excellent results for most secondary cleft rhinoplasties.

Development of the basement membrane and formation of collagen fibrils below the placodes in the head of anuran larvae

The development of the basement membrane and collagen fibrils below placodes, including the corneal region of the ectoderm, lens epithelium, nasal plate, and auditory vesicle in anuran larvae was observed by transmission electron microscopy and compared with that in nonplacodal regions such as the epidermis, neural tube, and optic vesicle. In the corneal region the lamina densa becomes thick concomitantly with the development of the connecting apparatuses such as hemidesmosomes and anchoring fibrils. The collagen fibrils increase in number and form a multilayered structure, showing similar morphology to the connective tissues below the epidermis. These two areas, i.e., the corneal region and epidermis, possess much collagenous connective tissue below them. On the other hand, the neural tube and ophthalmic vesicle that originated from the neural tube each have a thin lamina densa and a small number of underlying collagen fibrils. The lamina densa does not thicken and the number of collagen fibrils do not significantly increase during development. These two areas possess little extracellular matrix. The nasal plate and auditory vesicle show intermediate characteristics between the epidermis-type and the neural tube-type areas. In these areas, the lamina densa becomes thick and hemidesmosomes and anchoring fibrils develop. The number of collagen fibrils increases during development, but does not show an orderly arrangement; rather, they are randomly distributed. It is thought that the difference in the arrangement of collagen fibrils in different tissues is due to differences in the extracellular matrix around the collagen fibrils. Placodal epithelia have the same origin as epidermis, but during development their morphological characteristics differ and they are not associated with the pattern of extracellular matrix with characteristics of epidermal and corneal multilayered collagen fibril areas.

The cellular and molecular origins of beak morphology

Cellular and molecular mechanisms underlying differences in beak morphology likely involve interactions among multiple embryonic populations. We exchanged neural crest cells destined to participate in beak morphogenesis between two anatomically distinct species. Quail neural crest cells produced quail beaks in duck hosts and duck neural crest produced duck bills in quail hosts. These transformations involved morphological changes to non-neural crest host beak tissues. To achieve these changes, donor neural crest cells executed autonomous molecular programs and regulated gene expression in adjacent host tissues. Thus, neural crest cells are a source of molecular information that generates interspecific variation in beak morphology.

Staging criteria for embryos of the spiny softshell turtle, Apalone spinifera (Testudines: Trionychidae)

Previous work describing the embryonic stages of turtle development has not included members of the highly derived trionychid turtles. Staging criteria are described for the spiny softshell turtle (Apalone spinifera) to facilitate comparisons between phylogenetically distant taxa of turtles. Embryonic development in A. spinifera is placed in the context of the widely used sequence of Yntema stages. Novel features are included in the descriptions of staging criteria for Stages 13-26. Comparisons of the development of specific features are made between A. spinifera and other taxa of turtles. Data on the duration of developmental stages at different temperatures and embryo dimensions support the conclusion that morphology-based staging criteria are superior to developmental rate temperature coefficients.

In situ GABAergic modulation of synchronous gonadotropin releasing hormone-1 neuronal activity

Evidence indicates that gonadotropin releasing hormone-1 [GnRH-1, also known as luteinizing hormone releasing hormone (LHRH)] neurons can exhibit synchronized neuroendocrine secretory activity before entrance into the CNS. In this study, we used calcium imaging to evaluate patterns of activity in individual, embryonic, GnRH-1 neurons as well as population dynamics of GnRH-1 neurons in mouse nasal explants maintained for 1 versus 3 weeks. Independent of age, GnRH-1 neurons displayed significant calcium peaks that synchronized at an interval of approximately 20 min across multiple GnRH-1 cells within an explant. Acute tetrodotoxin treatment decreased the amplitude of calcium peaks in individual GnRH-1 neurons and the duration but not the frequency of synchronized activity in the population of GnRH-1 neurons. Acute GABA(B) receptor antagonism increased the frequency of synchronized neuronal activity at both ages, whereas acute GABA(A) receptor antagonism decreased calcium oscillations in individual GNRH-1 cells as well as synchronization of the calcium pulses within the GnRH-1 population at the 1 week time point to background non-GNRH-1 cell levels. These results indicate that developing GnRH-1 neurons rely heavily on GABAergic signaling to initiate synchronized bouts of activity but thereafter, possess an innate capacity for synchronized activity patterns that are modulated by, but not completely dependent on GABAergic signaling.

FGF signaling regulates expression of Tbx2, Erm, Pea3, and Pax3 in the early nasal region

Fgf8 is required for normal development of the nasal region. Here, we have used a candidate approach to identify genes that are induced in chick nasal mesenchyme in response to FGF signaling. Using an explant culture system, we show that expression of the transcription factors Tbx2, Erm, Pea3, and Pax3, but not Pax7, in nasal mesenchyme is regulated by ectodermal signals in a stage-dependent manner. Using beads soaked in recombinant FGF protein and an FGF receptor antagonist, we furthermore demonstrate that FGF signaling is necessary and sufficient for expression of Tbx2, Erm, Pea3, and Pax3, but has no effect on Pax7 expression. We also show that, within the nasal mesenchyme, competence to respond to FGF signaling is initially widespread and uniform but becomes restricted to regions normally exposed to FGF at later stages of development, coincident with changes in FGF receptor expression. Finally, we provide evidence that FGF8 also regulates Erm and Pea3 expression in the nasal placodes. Together, these results identify Tbx2, Erm, Pea3, and Pax3 as downstream targets of FGF signaling in the facial area and suggest that these genes may mediate some of the effects of FGF8 during development of the nasal region.

[Fetal ventilation and craniomaxillary development]

Data acquired by means of color Doppler ultrasound very explicitly suggest what the role of the fetal ventilation and nasal capsules in the morphogenesis of the maxillary prognathism, turbinates, nasal valves and nasopharynx could be. Furthermore, the dysmorphologies observed in Apert or Crouzon craniosynostosis, achondroplasia or unilateral cleft lip would also testify that the influence of the fetal ventilatory dynamics goes beyond the limits of the face and extends to the cranial base and the cranium. The wealth of raised hypothesis thanks to the contribution of this imaging system could question the validity of some conceptions of the fetal craniomaxillary morphogenesis.