A broad spectrum of biological activities has been proposed for transforming growth factor-beta 3 (TGF-beta 3). To study TGF-beta 3 function in development, TGF-beta 3 null mutant mice were generated by gene-targeting. Within 20 hours of birth, homozygous TGF-beta 3-/- mice die with unique and consistent phenotypic features including delayed pulmonary development and defective palatogenesis. Unlike other null mutants with cleft palate, TGF-beta 3-/- mice lack other concomitant craniofacial abnormalities. This study demonstrates an essential function for TGF-beta 3 in the normal morphogenesis of palate and lung, and directly implicates this cytokine in mechanisms of epithelial-mesenchymal interaction.

Cleft palate and skull malformations represent some of the most frequent congenital birth defects in the human population. Previous studies have shown that TGFβ signaling regulates the fate of the medial edge epithelium during palatal fusion and postnatal cranial suture closure during skull development. It is not understood, however, what the functional significance of TGFβ signaling is in regulating the fate of cranial neural crest (CNC)cells during craniofacial development. We show that mice with Tgfbr2conditional gene ablation in the CNC have complete cleft secondary palate,calvaria agenesis, and other skull defects with complete phenotype penetrance. Significantly, disruption of the TGFβ signaling does not adversely affect CNC migration. Cleft palate in Tgfbr2 mutant mice results from a cell proliferation defect within the CNC-derived palatal mesenchyme. The midline epithelium of the mutant palatal shelf remains functionally competent to mediate palatal fusion once the palatal shelves are placed in close contact in vitro. Our data suggests that TGFβ IIR plays a crucial, cell-autonomous role in regulating the fate of CNC cells during palatogenesis. During skull development, disruption of TGFβ signaling in the CNC severely impairs cell proliferation in the dura mater, consequently resulting in calvaria agenesis. We provide in vivo evidence that TGFβ signaling within the CNC-derived dura mater provides essential inductive instruction for both the CNC- and mesoderm-derived calvarial bone development. This study demonstrates that TGFβ IIR plays an essential role in the development of the CNC and provides a model for the study of abnormal CNC development.

Peripheral ossifying fibroma (POF) is a common solitary gingival growth thought to arise from the periodontal ligament. Though the etiology of POF remains unknown, some investigators consider it an inflammatory or reactive process, while others suggest it is a neoplastic process. In this report, we present and discuss a unique case of multicentric POF, affecting the maxillary and mandibular gingiva of a 49-year-old Caucasian female with meticulous oral hygiene and routine dental care. Though biopsy samples from multiple sites revealed similar histopathologic features, consistent with POF, the fact that there was a multicentric presentation is a unique phenomenon for this lesion. Multicentric lesions presenting in the oral and maxillofacial region are not typical, but have been observed in conditions associated with known genetic mutations, such as nevoid basal cell carcinoma syndrome (multiple odontogenic keratocysts), multiple endocrine neoplasia type II (multiple neuromas), neurofibromatosis (multiple neurofibromas) and Gardner syndrome (multiple neoplasms). This case is the first one to demonstrate that there may be a multicentric variant of POF that has not been previously recognized, and given the clinical presentation and multifocal nature of disease, the lesions in this patient are likely the result of genetic mutation(s) that predisposes to gingival soft tissue overgrowths containing mineralized product.

Craniofacial malformations are among the most frequent congenital birth defects in humans; cleft palate, that is inadequate fusion of the palatal shelves, occurs with an annual incidence of 1 in 700 to 1 in 1,000 live births among individuals of European descent. The secondary palate arises as bilateral outgrowths from the maxillary processes, and its formation depends on the coordinated development of craniofacial structures including the Meckel's cartilage and the mandible. Cleft lip and palate syndromes in humans are associated with polymorphisms in the gene (TGFA) encoding transforming growth factor-alpha (TGF-alpha), an epidermal growth factor receptor (EGFR) ligand made by most epithelia. Here we have characterized craniofacial development in Egfr-deficient (Egfr-/-) mice. Newborn Egfr-/- mice have facial mediolateral defects including narrow, elongated snouts, underdeveloped lower jaw and a high incidence of cleft palate. Palatal shelf explants from Egfr-/- mice fused, but frequently had residual epithelium in the midline. In addition, morphogenesis of Meckel's cartilage was deficient in cultured mandibular processes from Egfr-/- embryos. The secretion of matrix metalloproteinases (MMPs) was diminished in Egfr-/- explants, consistent with the ability of EGF to increase MMP secretion and with the decreased MMP expression caused by inhibition of Egfr signalling in wild-type explants. Accordingly, inactivation of MMPs in wild-type explants phenocopied the defective morphology of Meckel's cartilage seen in Egfr-/- explants. Our results indicate that EGFR signalling is necessary for normal craniofacial development and that its role is mediated in part by its downstream targets, the MMPs, and may explain the genetic correlation of human cleft palate with polymorphisms in TGFA.

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The past decade has seen increasing demands for reform of

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