Differential expression of retinoic acid-synthesizing (RALDH) enzymes during fetal development and organ differentiation in the mouse.
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Three retinaldehyde dehydrogenases (RALDH1, RALDH2 and RALDH3), which catalyze the oxidation of retinaldehyde into retinoic acid, have been shown to be differentially expressed during early embryogenesis. Here, we report their differential expression patterns throughout later mouse organogenesis. Raldh1 is prominently expressed in developing lung (notably in bronchial and tracheal epithelia), and shows stage-specific expression in stomach and intestine epithelial and mesenchymal layers. Raldh3 expression is specific to the differentiating intestinal lamina propria. Raldh2 is expressed throughout the kidney nephrogenic zone, whereas Raldh1 and Raldh3 are mostly expressed in collecting duct epithelia. Raldh3 expression is more restricted than that of Raldh1 in the urogenital tract and sex gland epithelia, whereas Raldh2 expression is mesenchymal. Raldh1 is coexpressed with Raldh2 in the early heart epicardium, and is later specifically expressed in developing heart valves. All three genes exhibit distinct expression patterns in respiratory and olfactory epithelia and/or mesenchymes, and in developing teeth. Only Raldh1 expression is seen after birth in specific brain structures. These data indicate a requirement for regulated RA synthesis in various differentiating organs. (+info)
The Caenorhabditis elegans homolog of FGD1, the human Cdc42 GEF gene responsible for faciogenital dysplasia, is critical for excretory cell morphogenesis.
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FGD1 mutations result in faciogenital dysplasia, an X-linked human disease that affects skeletogenesis. FGD1 encodes a guanine nucleotide exchange factor (GEF) that specifically activates the Rho GTPase Cdc42. To gain insight into the function of FGD1, we have isolated and characterized fgd-1, the Caenorhabditis elegans homolog of the human FGD1 gene. Comparative sequence analyses show that fgd-1 and FGD1 share a similar structural organization and a high degree of sequence identity throughout shared signaling domains. In nematodes, interference with fgd-1 expression results in excretory cell abnormalities and cystic dilation of the excretory cell canals. Molecular lesions associated with two exc-5 alleles affect the fgd-1 gene, and fgd-1 transgenic expression rescues the Exc-5 phenotype. Together, these data confirm that the fgd-1 transcript corresponds to the exc-5 gene. Transgenic expression studies show that fgd-1 has a limited pattern of expression that is confined to the excretory cell during development, a finding that suggests that the C.elegans FGD-1 protein might function in a cell autonomous manner. Serial observations indicate that fgd-1 mutations lead to developmental excretory cell abnormalities that cause cystic dilation and interfere with canal process extension. Based on these data, we conclude that fgd-1 is the C.elegans homolog of the human FGD1 gene, a new member of the FGD1-related family of RhoGEF genes, and that fgd-1 plays a critical role in excretory cell morphogenesis and cellular organization. (+info)
Interactions between Hox-negative cephalic neural crest cells and the foregut endoderm in patterning the facial skeleton in the vertebrate head.
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The vertebrate face contains bones that differentiate from mesenchymal cells of neural crest origin, which colonize the median nasofrontal bud and the first branchial arches. The patterning of individual facial bones and their relative positions occurs through mechanisms that remained elusive. During the early stages of head morphogenesis, an endodermal cul-de-sac, destined to become Sessel's pouch, underlies the nasofrontal bud. Reiterative outpocketings of the foregut then form the branchial pouches. We have tested the capacity of endoderm of the avian neurula to specify the facial skeleton by performing ablations or grafts of defined endodermal regions. Neural crest cells that do not express Hox genes respond to patterning cues produced regionally in the anterior endoderm to yield distinct skeletal components of the upper face and jaws. However, Hox-expressing neural crest cells do not respond to these cues. Bone orientation is likewise dependent on the position of the endoderm relative to the embryonic axes. Our findings thus indicate that the endoderm instructs neural crest cells as to the size, shape and position of all the facial skeletal elements, whether they are cartilage or membrane bones. (+info)
The effect of increasing vertical dimension of occlusion on facial aesthetics.
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AIM: To investigate the effect of increasing the vertical dimension of occlusion on facial aesthetics. SETTING: General practice. METHOD: Questionnaires were sent to 96 patients who had been treated in the practice during the period of July 1998 to December 2000, resulting in an overall 72% response rate. All these patients had had their occlusal vertical dimension increased. Photographs of patients were taken before, during and after treatment. The questionnaire asked their opinion on the effects of the treatment on their facial features. To obtain an objective view to substantiate the opinions of the patients, a panel of five judges reviewed the before and after photographs and filled in their own questionnaires. RESULTS: Of the patients who responded to the questionnaire, 79.7% said they looked younger after the treatment. The panel thought 81.2% of the patients treated whose photographs they reviewed looked younger. CONCLUSION: Increasing the vertical dimension of occlusion can have far reaching effects on facial aesthetics, not just on the peri-oral areas but on the whole face. (+info)
Morphological differences in the craniofacial structure between Japanese and Caucasian girls with Class II Division 1 malocclusions.
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The craniofacial features of 49 Japanese and 75 British Caucasian girls with Class II division 1 malocclusions were evaluated from lateral cephalometric radiographs, and the morphological differences between both races were examined. The subjects' ages ranged from 11 years 1 month to 12 years 11 months. The mean values of 13 linear and 13 angular cephalometric parameters were compared. The Japanese Class II division 1 sample had a significantly shorter anterior cranial base length (S-N; P < 0.001) and a more obtuse articular angle (S-Ar-Go; P < 0.001). Analysis of the dentoalveolar components in Japanese subjects showed more proclined lower incisors (L1/Go-Me; P < 0.05) and a steeper occlusal plane (Occ.P/S-N; P < 0.01) relative to those of Caucasians. The short anterior cranial base length and excessive vertical development in the Japanese population might be common racial morphological features, but the main reason for the Class II division 1 skeletal disharmony in both races was different; it was caused by the anteriorly positioned maxilla in Caucasians and the backward rotated mandible in the Japanese. (+info)
Computed tomography characteristics of non-syndromic craniofacial fibrous dysplasia.
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BACKGROUND: Fibrous dysplasia is a benign fibro-osseous tumor of bones commonly involving the craniofacial region. Computed tomography (CT) imaging study of the disease is useful for evaluation and treatment planning. However, few studies have evaluated such large patient series. METHODS: A total of 46 patients with complete medical records and CT images was included in this study. All of these patients were non-syndromic, had fibrous dysplasia involving only the craniofacial region, and had no skin pigmentation or other evidence of endocrine problems. Data analyses were performed on the clinical manifestations, time of onset, signs and symptoms, involvement of cranial and facial bones, and CT appearance of the tumors in this patient group. RESULTS: Painless swelling was the chief clinical problem in 78% of patients, followes by dental malocclusion in 22%. Onset of the disease was reported to have occurred before 6 years of age in 34%, between 6 and 10 years in 27%, and older than 10 years in 39% of patients. Extreme timings such as onset at infancy or older than 20 years of age were also noted. The average number of bones involved was 3.2 bones per patient. Involvement of more than one craniofacial bone occurred in 70% of patients. The maxilla, orbital, and frontal bones were most commonly involved. CT images appeared sclerotic or homogenous in 34%, mixed white and dark or heterogenous in 55%, and cystic in 11%. A correlation between the age of onset of the disease and the number of bones involved was not observed. CONCLUSIONS: Findings of this study demonstrate that craniofacial fibrous dysplasia displays a wide spectrum of clinical behaviors. CT imaging generally revealed extensive involvement of the tumor in the craniofacial region. (+info)
Craniodental variation among Macaques (Macaca), nonhuman primates.
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BACKGROUND: In terms of structure and function, the skull is one of the most complicated organs in the body. It is also one of the most important parts in terms of developmental and evolutionary origins. This complexity makes it difficult to obtain evolutionary assessments if, as is usually the case with fossils, only part of the skull is available. For this reason this study involves a set of comparisons whereby the smallest functional units are studied first, and these built up, through a triple-nested hierarchical design, into more complex anatomical regions and eventually into the skull-as-a-whole. This design has been applied to macaques (Macaca) in order to reveal patterns of variation at the different levels. The profiles of such variation have been obtained both within and between species. This has lead to a search for the skull parts that have undergone similar selection pressures during evolution and comparable development patterns in both ontogeny and phylogeny. RESULTS: Morphometric analysis (Principal Components) was used to obtain these profiles of species and sex separations based on 77 cranial variables from 11 species of macaques. The results showed that 7 functional units could be aggregated into three functionally reasonable anatomical regions on the basis of similarities in profiles. These were: the masticatory apparatus containing mandible, lower teeth and upper teeth, the face as a whole combining maxilla (actually lower face) and upper face, and the cranium as a whole involving cranium and calvaria. Twenty-six variables were finally selected for analyzing the morphology of the whole skull. This last showed an overall profile similar to that revealed in the masticatory apparatus but also contained additional information pertaining to individual species and species-groups separations. CONCLUSIONS: The study provides a model for carrying out analysis of species separations and sex variation simultaneously. Through this design it seems possible to see cranio-dental elements that may result from similar developmental processes, have similar functional adaptations, and show an appropriately integrated structure morphologically. This study also implies that the biological information drawn from part of skull alone, e.g. as in studies of incomplete fossils may provide misleading information. (+info)
The Dlx5 and Dlx6 homeobox genes are essential for craniofacial, axial, and appendicular skeletal development.
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Dlx homeobox genes are mammalian homologs of the Drosophila Distal-less (Dll) gene. The Dlx/Dll gene family is of ancient origin and appears to play a role in appendage development in essentially all species in which it has been identified. In Drosophila, Dll is expressed in the distal portion of the developing appendages and is critical for the development of distal structures. In addition, human Dlx5 and Dlx6 homeobox genes have been identified as possible candidate genes for the autosomal dominant form of the split-hand/split-foot malformation (SHFM), a heterogeneous limb disorder characterized by missing central digits and claw-like distal extremities. Targeted inactivation of Dlx5 and Dlx6 genes in mice results in severe craniofacial, axial, and appendicular skeletal abnormalities, leading to perinatal lethality. For the first time, Dlx/Dll gene products are shown to be critical regulators of mammalian limb development, as combined loss-of-function mutations phenocopy SHFM. Furthermore, spatiotemporal-specific transgenic overexpression of Dlx5, in the apical ectodermal ridge of Dlx5/6 null mice can fully rescue Dlx/Dll function in limb outgrowth. (+info)