Palate In Mice Research Articles

MiR-200b regulates cell migration via Zeb family during mouse palate development

Palate development requires coordinating proper cellular and molecular events in palatogenesis, including the epithelial-mesenchymal transition (EMT), apoptosis, cell proliferation, and cell migration. Zeb1 and Zeb2 regulate epithelial cadherin (E-cadherin) and EMT during organogenesis. While microRNA 200b (miR-200b) is known to be a negative regulator of Zeb1 and Zeb2 in cancer progression, its regulatory effects on Zeb1 and Zeb2 in palatogenesis have not yet been clarified. The aim of this study is to investigate the relationship between the regulators of palatal development, specifically, miR-200b and the Zeb family. Expression of both Zeb1 and Zeb2 was detected in the mesenchyme of the mouse palate, while miR-200b was expressed in the medial edge epithelium. After contact with the palatal shelves, miR-200b was expressed in the palatal epithelial lining and epithelial island around the fusion region but not in the palatal mesenchyme. The function of miR-200b was examined by overexpression via a lentiviral vector in the palatal shelves. Ectopic expression of miR-200b resulted in suppression of the Zeb family, upregulation of E-cadherin, and changes in cell migration and palatal fusion. These results suggest that miR-200b plays crucial roles in cell migration and palatal fusion by regulating Zeb1 and Zeb2 as a noncoding RNA during palate development.

Fibroblast Growth Factor 9 (FGF9)-Pituitary Homeobox 2 (PITX2) Pathway Mediates Transforming Growth Factor β (TGFβ) Signaling to Regulate Cell Proliferation in Palatal Mesenchyme during Mouse Palatogenesis

Cleft palate represents one of the most common congenital birth defects. Transforming growth factor β (TGFβ) signaling plays crucial functions in regulating craniofacial development, and loss of TGFβ receptor type II in cranial neural crest cells leads to craniofacial malformations, including cleft palate in mice (Tgfbr2(fl/fl);Wnt1-Cre mice). Here we have identified candidate target genes of TGFβ signaling during palatal formation. These target genes were selected based on combining results from gene expression profiles of embryonic day 14.5 palates from Tgfbr2(fl/fl);Wnt1-Cre mice and previously identified cleft palate phenotypes in genetically engineered mouse models. We found that fibroblast growth factor 9 (Fgf9) and transcription factor pituitary homeobox 2 (Pitx2) expressions are significantly down-regulated in the palate of Tgfbr2(fl/fl);Wnt1-Cre mice, and Fgf9 and Pitx2 loss of function mutations result in cleft palate in mice. Pitx2 expression is down-regulated by siRNA knockdown of Fgf9, suggesting that Fgf9 is upstream of Pitx2. We detected decreased expression of both cyclins D1 and D3 in the palates of Tgfbr2(fl/fl);Wnt1-Cre mice, consistent with the defect in cell proliferation. Significantly, exogenous FGF9 restores expression of cyclins D1 and D3 in a Pitx2-dependent manner and rescues the cell proliferation defect in the palatal mesenchyme of Tgfbr2(fl/fl);Wnt1-Cre mice. Our study indicates that a TGFβ-FGF9-PITX2 signaling cascade regulates cranial neural crest cell proliferation during palate formation.

The Potential Role for Corticosterone in the Induction of Cleft Palate in Mice After Treatment With a Selective NK‐1 Receptor Antagonist, Casopitant (GW679769B)

Casopitant is a potent and selective NK-1 receptor antagonist that has shown clinical efficacy in the prevention of chemotherapy-induced and postoperative-induced nausea and vomiting. In an embryo-fetal development study, pregnant mice were given vehicle (sterile water) or doses of 30, 100, or 300 mg/kg/day casopitant on Gestation Day (GD) 6 to 15. Fetuses were evaluated for external, visceral, and skeletal abnormalities on GD 18. In a follow-on study to investigate casopitant-induced hormonal changes during the developmental period for palate formation, pregnant mice were given vehicle (sterile water) or 300 mg/kg/day casopitant once daily on GD 6 to 13. Blood was collected on GD 13 at various time-points for measurement of plasma adrenocorticotropic hormone and corticosterone (CRT) concentrations. There was no evidence of developmental toxicity in mice at 30 or 100 mg/kg/day but 9% of fetuses at 300 mg/kg/day had cleft palate. Mice are sensitive to glucocorticoid-induced cleft palates, and NK-1 antagonists are known to modulate the hypothalamic-pituitary-adrenal axis leading to increases in corticosterone. On GD 13, mean plasma adrenocorticotropic hormone levels at 300 mg/kg/day were elevated by approximately twofold from vehicle-treated levels at 1 hr post-dose and mean plasma CRT levels were elevated by 3, 5, and 10-fold at 0.5, 1, and 2 hr post-dose, respectively. The increased level of CRT was in the range previously shown in the literature to cause cleft palates in mice and was likely the underlying mechanism behind casopitant-induced cleft palate in mice.

MiR-200b is involved in Tgf-β signaling to regulate mammalian palate development

Various cellular and molecular events are involved in palatogenesis, including apoptosis, epithelial-mesenchymal transition (EMT), cell proliferation, and cell migration. Smad2 and Snail, which are well-known key mediators of the transforming growth factor beta (Tgf-β) pathway, play a crucial role in the regulation of palate development. Regulatory effects of microRNA 200b (miR-200b) on Smad2 and Snail in palatogenesis have not yet been elucidated. The aim of this study is to determine the relationship between palate development regulators miR-200b and Tgf-β-mediated genes. Expression of miR-200b, E-cadherin, Smad2, and Snail was detected in the mesenchyme of the mouse palate, while miR-200b was expressed in the medial edge epithelium (MEE) and palatal mesenchyme. After the contact of palatal shelves, miR-200b was no longer expressed in the mesenchyme around the fusion region. The binding activity of miR-200b to both Smad2 and Snail was examined using a luciferase assay. MiR-200b directly targeted Smad2 and Snail at both cellular and molecular levels. The function of miR-200b was determined by overexpression via a lentiviral vector in the palatal shelves. Ectopic expression of miR-200b resulted in suppression of these Tgf-β-mediated regulators and changes of apoptosis and cell proliferation in the palatal fusion region. These results suggest that miR-200b plays a crucial role in regulating the Smad2, Snail, and in apoptosis during palatogenesis by acting as a direct non-coding, influencing factor. Furthermore, the molecular interactions between miR-200b and Tgf-β signaling are important for proper palatogenesis and especially for palate fusion. Elucidating the mechanism of palatogenesis may aid the design of effective gene-based therapies for the treatment of congenital cleft palate.

Mechanism of cleft palate in mice induced by 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin

To explore the mechanism of cleft palate in mice induced by 2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD). On gestation day 10 (GD 10), 12 pregnant mice were randomly divided into two groups as the treated group and the control group with 6 mice in each group. The mice in the treated group received intragastric administration with 64 microg TCDD/kg, while the mice in the control group received equivalent corn oil. The embryos were examined under stereomicroscope to detect the incidence of cleft palate on GD 18.5. Another 18 pregnant mice were randomly divided into two groups (treated group and control group) on GD 10 with 9 pregnant mice in each group. Then each group was divided into 3 subgroups: GD 13.5, GD 14.5 and GD 15.5, with 3 pregnant mice in each subgroup. The palatal shelves were dissected from the embryos for RNA and DNA extraction on GD 13.5, GD 14.5 and GD 15.5. At last the expression of Smad 2-4 and Smad 7 mRNA was investigated by RT-PCR, and the TGF-beta3 promoter methylamine levels were investigated by methylation specific PCR (MSP). The cleft palate mice model was established successfully by exposing pregnant C57BL/6J mice to TCDD. Total frequency of clefts was 100% in TCDD group, and the frequency of clefts was 0 in the control group. The relative expression of Smad 2 mRNA was 0.263 +/- 0.088, 0.296 +/- 0.016 and 0.159 +/- 0.027 in TCDD group, 0.180 +/- 0.042, 0.282 +/- 0.029 and 0.165 +/- 0.018 in control group. The relative expression of Smad 3 mRNA was 0.453 +/- 0.153, 0.551 +/- 0.160 and 0.328 +/- 0.049 in TCDD group, 0.375 +/- 0.126, 0.510 +/- 0.145 and 0.259 +/- 0.035 in control group. The relative expression of Smad 4 mRNA was 0.675 +/- 0.174, 0.577 +/- 0.070 and 0.396 +/- 0.066 in TCDD group, 0.557 +/- 0.138, 0.587 +/- 0.080 and 0.441 +/- 0.054 in control group. The relative expression of Smad 7 mRNA was 0.283 +/- 0.050, 0.320 +/- 0.068 and 0.169 +/- 0.045 in TCDD group, 0.207 +/- 0.043, 0.288 +/- 0.051 and 0.155 +/- 0.040 in control group. There was no significant difference between the TCDD treated mice and the control (P > 0.05). The TGF-beta3 promoters were at the un-methylation state both in the TCDD treated and control group. It suggests that TCDD could induce a stable formation of cleft palate, but it is not through the TGF-beta/Smad signaling nor through the modification of TGF-beta3 promoter methylation.

Role of Indian Hedgehog Signaling in Palatal Osteogenesis

Cleft lip-cleft palate is a common congenital disability and represents a large biomedical burden. Through the use of animal models, the molecular underpinnings of cleft palate are becoming increasingly clear. Indian hedgehog (Ihh) has been shown to be associated with craniofacial development and to be active in the palatine bone. The authors hypothesize that Indian hedgehog activity plays a role in osteogenesis within the secondary palate and that defects in this pathway may inhibit osteogenesis of the secondary palate. Palates were isolated from wild-type mice during the period of palate development (embryonic days 9.5 to 17.5). Quantitative real-time polymerase chain reaction was used for detecting gene expression during osteogenic differentiation and cellular differentiation (Shh, Ihh, Ptc1, Gli1, Gli2, Gli3, Runx2, Alp, and Col1a1). Next, palates were analyzed by hematoxylin and eosin, aniline blue, pentachrome, and in situ hybridization to assess osteogenesis of the palatal shelf and expression of hedgehog pathway genes. Finally, the palates of Indian hedgehog-null mice were analyzed to determine the effect of genetic deficiency on palatal development osteogenesis. Increased Indian hedgehog and osteogenic signaling coincided with ossification and fusion of the palate in wild-type mice. This included a fivefold to 150-fold peak in expression of hedgehog elements, including Ihh, at embryonic day 15.5 as compared with embryonic day 9.5. Contrarily, loss of Indian hedgehog by genetic knockout (Ihh-/-) resulted in decreased secondary palate ossification. The authors' results suggest a role for hedgehog signaling during palatal ossification. The hedgehog pathway is activated during palatal fusion, and deletion of Indian hedgehog leads to diminished ossification of the secondary hard palate.

Occurrence of Cleft-Palate and Alteration of Tgf-β3 Expression and the Mechanisms Leading to Palatal Fusion in Mice following Dietary Folic-Acid Deficiency

Folic acid (FA) is essential for numerous bodily functions. Its decrease during pregnancy has been associated with an increased risk of congenital malformations in the progeny. The relationship between FA deficiency and the appearance of cleft palate (CP) is controversial, and little information exists on a possible effect of FA on palate development. We investigated the effect of a 2–8 weeks’ induced FA deficiency in female mice on the development of CP in their progeny as well as the mechanisms leading to palatal fusion, i.e. cell proliferation, cell death, and palatal-shelf adhesion and fusion. We showed that an 8 weeks’ maternal FA deficiency caused complete CP in the fetuses although a 2 weeks’ maternal FA deficiency was enough to alter all the mechanisms analyzed. Since transforming growth factor-β₃ (TGF-β₃) is crucial for palatal fusion and since most of the mechanisms impaired by FA deficiency were also observed in the palates of Tgf-β₃null mutant mice, we investigated the presence of TGF-β₃ mRNA, its protein and phospho-SMAD2 in FA-deficient (FAD) mouse palates. Our results evidenced a large reduction in Tgf-β₃ expression in palates of embryos of dams fed an FAD diet for 8 weeks; Tgf-β₃ expression was less reduced in palates of embryos of dams fed an FAD diet for 2 weeks. Addition of TGF-β₃ to palatal-shelf cultures of embryos of dams fed an FAD diet for 2 weeks normalized all the altered mechanisms. Thus, an insufficient folate status may be a risk factor for the development of CP in mice, and exogenous TGF-β₃ compensates this deficit in vitro.

Bmpr1a signaling plays critical roles in palatal shelf growth and palatal bone formation

Cleft palate, including submucous cleft palate, is among the most common birth defects in humans. While overt cleft palate results from defects in growth or fusion of the developing palatal shelves, submucous cleft palate is characterized by defects in palatal bones. In this report, we show that the Bmpr1a gene, encoding a type I receptor for bone morphogenetic proteins (Bmp), is preferentially expressed in the primary palate and anterior secondary palate during palatal outgrowth. Following palatal fusion, Bmpr1a mRNA expression was upregulated in the condensed mesenchyme progenitors of palatal bone. Tissue-specific inactivation of Bmpr1a in the developing palatal mesenchyme in mice caused reduced cell proliferation in the primary and anterior secondary palate, resulting in partial cleft of the anterior palate at birth. Expression of Msx1 and Fgf10 was downregulated in the anterior palate mesenchyme and expression of Shh was downregulated in the anterior palatal epithelium in the Bmpr1a conditional mutant embryos, indicating that Bmp signaling regulates mesenchymal-epithelial interactions during palatal outgrowth. In addition, formation of the palatal processes of the maxilla was blocked while formation of the palatal processes of the palatine was significantly delayed, resulting in submucous cleft of the hard palate in the mutant mice. Our data indicate that Bmp signaling plays critical roles in the regulation of palatal mesenchyme condensation and osteoblast differentiation during palatal bone formation.

Cooperation of two ADAMTS metalloproteases in closure of the mouse palate identifies a requirement for versican proteolysis in regulating palatal mesenchyme proliferation

We have identified a role for two evolutionarily related, secreted metalloproteases of the ADAMTS family, ADAMTS20 and ADAMTS9, in palatogenesis. Adamts20 mutations cause the mouse white-spotting mutant belted (bt), whereas Adamts9 is essential for survival beyond 7.5 days gestation (E7.5). Functional overlap of Adamts9 with Adamts20 was identified using Adamts9(+/-);bt/bt mice, which have a fully penetrant cleft palate. Palate closure was delayed, although eventually completed, in both Adamts9(+/-);bt/+ and bt/bt mice, demonstrating cooperation of these genes. Adamts20 is expressed in palatal mesenchyme, whereas Adamts9 is expressed exclusively in palate microvascular endothelium. Palatal shelves isolated from Adamts9(+/-);bt/bt mice fused in culture, suggesting an intact epithelial TGFβ3 signaling pathway. Cleft palate resulted from a temporally specific delay in palatal shelf elevation and growth towards the midline. Mesenchyme of Adamts9(+/-);bt/bt palatal shelves had reduced cell proliferation, a lower cell density and decreased processing of versican (VCAN), an extracellular matrix (ECM) proteoglycan and ADAMTS9/20 substrate, from E13.5 to E14.5. Vcan haploinsufficiency led to greater penetrance of cleft palate in bt mice, with a similar defect in palatal shelf extension as Adamts9(+/-);bt/bt mice. Cell density was normal in bt/bt;Vcan(hdf)(/+) mice, consistent with reduced total intact versican in ECM, but impaired proliferation persisted in palate mesenchyme, suggesting that ADAMTS-cleaved versican is required for cell proliferation. These findings support a model in which cooperative versican proteolysis by ADAMTS9 in vascular endothelium and by ADAMTS20 in palate mesenchyme drives palatal shelf sculpting and extension.

Analysis of the Presence of Cell Proliferation-Related Molecules in the Tgf-β3 Null Mutant Mouse Palate Reveals Misexpression of EGF and Msx-1

The Tgf-β₃ null mutant mouse palate presents several cellular anomalies that lead to the appearance of cleft palate. One of them concerns the cell proliferation of both the palatal medial edge epithelium and mesenchyme. In this work, our aim was to determine whether there was any variation in the presence/distribution of several cell proliferation-related molecules that could be responsible for the cell proliferation defects observed in these palates. Our results showed no difference in the presence of EGF-R, PDGF-A, TGF-β₂, Bmp-2, and Bmp-4, and differences were minimal for FGF-10 and Shh. However, the expression of EGF and Msx-1 changed substantially. The shift of the EGF protein expression was the one that most correlated with that of cell proliferation. This molecule is regulated by TGF-β₃, and experiments blocking its activity in culture suggest that EGF misexpression in the Tgf-β₃ null mutant mouse palate plays a role in the cell proliferation defect observed.

A Metabonomic Approach to Analyze the Dexamethasone‐Induced Cleft Palate in Mice

Mice models are an important way to understand the relation between the fetus with cleft palate and changes of maternal biofluid. This paper aims to develop a metabonomics approach to analyze dexamethasone-induced cleft palate in pregnant C57BL/6J mice and to study the relationship between the change of endogenous small molecular metabolites in maternal plasma and the incidence of cleft palate. To do so, pregnant mice were randomly divided into two groups. The one group was injected with dexamethasone. On E17.5th day, the incident rates of cleft palate from embryos in two groups were calculated. The 1H-NMR spectra from the metabolites in plasma in two groups was collected at same time. Then the data were analyzed using metabonomics methods (PCA and SIMCA). The results showed that the data from the two groups displayed distinctive characters, and the incidence of cleft palate were significantly different (P < .005). To conclude, this study demonstrates that the metabonomics approach is a powerful and effective method in detecting the abnormal metabolites from mother in the earlier period of embryos, and supports the idea that a change from dexamethasone induced in maternal metabolites plays an important role in the incidence of cleft palate.

Cooperation between the transcription factors p63 and IRF6 is essential to prevent cleft palate in mice.

Cleft palate is a common congenital disorder that affects up to 1 in 2,500 live human births and results in considerable morbidity to affected individuals and their families. The etiology of cleft palate is complex, with both genetic and environmental factors implicated. Mutations in the transcription factor-encoding genes p63 and interferon regulatory factor 6 (IRF6) have individually been identified as causes of cleft palate; however, a relationship between the key transcription factors p63 and IRF6 has not been determined. Here, we used both mouse models and human primary keratinocytes from patients with cleft palate to demonstrate that IRF6 and p63 interact epistatically during development of the secondary palate. Mice simultaneously carrying a heterozygous deletion of p63 and the Irf6 knockin mutation R84C, which causes cleft palate in humans, displayed ectodermal abnormalities that led to cleft palate. Furthermore, we showed that p63 transactivated IRF6 by binding to an upstream enhancer element; genetic variation within this enhancer element is associated with increased susceptibility to cleft lip. Our findings therefore identify p63 as a key regulatory molecule during palate development and provide a mechanism for the cooperative role of p63 and IRF6 in orofacial development in mice and humans.

Is it possible to antagonize 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin- induced cleft palate by prenatal administration of folic acid? An experimental study

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can cause a high percentage of cleft palate in fetuses when administered during organogenesis in certain strains of mice including C57BL/6J. In this study, folic acid (FA) was tested for antiteratogenic effects on TCDD-induced cleft palate in fetal mice. The pregnant C57BL/6J mice were dosed with 24 microg TCDD/kg and/or 5 mg, 10 mg, 20 mg, 40 mg FA/kg body weight on gestation day (GD) 10. The control group mice received 50 mL sesame oil/kg body weight on GD10. The mice were sacrificed on GD12.5, GD13.5, GD14.5, GD15.5, and GD16.5. The harvested embryos were examined to detect the incidence of cleft palate and the developing palatal shelves on different phases were investigated morphologically and histologically among different groups. Total frequency of clefts was 55.56% in TCDD group and 17.50% (5 mg), 42.85% (10 mg), 42.10% (20 mg), 28.26% (40 mg) in TCDD + FA groups. FA (5 mg) reduced the incidence of the cleft palate from 55.56% to 17.50% (p = 0.005). There were no significant differences between the TCDD group and 10 mg, 20 mg, 40 mg TCDD + FA groups. Based on the these results, the present study suggests that FA can reduce the incidence of 2,3,7,8-TCDD-induced cleft palate in mice.

Association Between Bone Morphogenetic Protein 4 Gene Polymorphisms with Nonsyndromic Cleft Lip with or without Cleft Palate in a Chilean Population

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is one of the most common birth defects in humans with both genetic and environmental components involved in its expression. Experimental evidences have postulated that bone morphogenetic protein 4 gene (Bmp4) is involved in the etiology of cleft lip with or without cleft palate (CL/P) in mice. In our study we analyzed the association between BMP4 and NSCLP in a sample of 150 unrelated trios ascertained through affected probands. Three BMP4 polymorphisms were analyzed, two intronic (rs762642 and rs2855532) and rs1957860, located 5.7 kb upstream from BMP4. Transmission/disequilibrium tests were performed at the allele and haplotype levels. Our results did not detect preferential transmission for individual single-nucleotide polymorphisms. Significant transmission distortion was observed for haplotypes rs1957860-rs762642 (p = 0.018), especially for C-T (p = 0.015) and T-T (p = 0.018) which include the genomic region where the promoter and an enhancer of BMP4 are located. Thus, despite the positive association detected between these haplotypes and NSCLP they probably do not have a functional effect on BMP4 expression or protein activity but possibly reflect NSCLP susceptibility changes which are in linkage disequilibrium with these polymorphisms. The findings of our study support a role for BMP4 in NSCLP in the admixed Chilean population.

Experimental study on protection of vitamin B6 on TCDD‐induced palatal cleft formation in the mice

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) can cause a high percentage of cleft palate in fetuses when administered during organogenesis in certain strains of mice including the C57BL/6J. In this study, vitamin B(6) (B(6)) was tested for antiteratogenic effects on TCDD-induced cleft palate in fetal mice. The pregnant C57BL/6J mice were dosed with 24 microg TCDD/kg and/or 5, 10, 20, and 40 mg B(6)/kg body weight on gestation day (GD) 10. The control group mice were dosed with 50 ml sesame oil/kg body weight on GD10. The mice were sacrificed on GD12.5, GD13.5, GD14.5, GD15.5, and GD17.5, respectively. The harvested embryos were examined to detect the incidence of cleft palate and the developing palatal shelves in a different phase were investigated morphologically and histologically among different groups. Total frequency of clefts is 55.56% in the TCDD group and 31.81% (5 mg), 44.44% (10 mg), 40.90% (20 mg), and 32.00% (40 mg) in the TCDD+ B(6) groups. There were no statistically significant differences among the TCDD and TCDD+ B(6) groups (p = 0.743 > 0.05). It was demonstrated in this study that B6 could not antagonize 2, 3, 7, 8-TCDD-indued cleft palate.

Interactions between TGF- β1 and TGF- β3 and their role in medial edge epithelium cell death and palatal fusion in vitro

In recent decades, studies have shown that both TGF- β 1 and TGF- β 3 play an important role in the induction of medial edge epithelium (MEE) cell death and palatal fusion. Many of these experiments involved the addition or blockage of one of these growth factors in wild-type (WT) mouse palate cultures, where both TGF- β 1 and TGF- β 3 are present. Few studies have addressed the existence of interactions between TGF- β 1 and TGF- β 3, which could modify their individual roles in MEE cell death during palatal fusion. We carried out several experiments to test this possibility, and to investigate how this could influence TGF- β 1 and TGF- β 3 actions on MEE cell death and palatal shelf fusion. We double-immunolabelled developing mouse palates with anti-TGF- β 1 or anti-TGF- β 3 antibodies and TUNEL, added rhTGF- β 1 or rhTGF- β 3 or blocked the TGF- β 1 and TGF- β 3 action at different concentrations to WT or Tgf-β 3 null mutant palate cultures, performed in situ hybridizations with Tgf-β 1 or Tgf-β 3 riboprobes, and measured the presence of TUNEL-positive midline epithelial seam (MES) cells and MES disappearance (palatal shelf fusion) in the different in vitro conditions. By combining all these experiments, we demonstrate great interaction between TGF- β 1 and TGF- β 3 in the developing palate and confirm that TGF- β 3 has a more active role in MES cell death than TGF- β 1, although both are major inductors of MES disappearance. Finally, the co-localization of TGF- β 1, but not TGF- β 3, with TUNEL in the MES allows us to suggest a possible role for TGF- β 1 in MES apoptotic clearance.

An Orthotopic Murine Model of Sinonasal Malignancy

Malignant sinonasal tumors are clinically challenging due to their proximity to vital structures and their diverse histogenesis and biological behavior. To date, no animal models accurately reflect the clinical behavior of these malignancies. We developed an orthotopic murine model of sinonasal malignancy that reproduces the intracranial extension, bony destruction, and spread along neural fascial planes seen in patients with aggressive sinonasal malignancies of various histologies. Human squamous cell carcinoma line (DM14) and adenoid cystic carcinoma line (ACC-3) were implanted in the right maxillary sinus or soft palate in male nude mice. Animals were monitored for tumor growth and survival. Tumor specimens were removed for histopathologic evaluation to assess for intracranial extension, orbital invasion, bony invasion, perineural invasion, and distant metastasis. Statistical analysis was done to calculate P values with the Student's t test for individual tumor volumes. Differences in survival times were assessed using the log-rank test. Mice with DM14 or ACC-3 implanted in either the maxillary sinus or the soft palate developed large primary tumors. A statistically significant inverse correlation between survival and the number of tumor cells implanted was found. Histopathologic evaluation revealed orbital invasion, intracranial extension, pulmonary metastasis, lymph node metastasis, and perineural invasion. We describe the first orthotopic model for sinonasal malignancy. Our model faithfully recapitulates the phenotype and malignant behavior of the aggressive tumor types seen in patients. This model offers an opportunity to identify and specifically target the aberrant molecular mechanisms underlying this heterogeneous group of malignancies.

Congenital Anomalies Induced by Triamcinolone Acetonide in Murine Embryos

We have studied the morphogenesis of anorectal malformations in mice using retinoids. Several investigators have reported an interaction between glucocorticoids and retinoids. It was supposed that glucocorticoids had some effects on the morphogenesis of murine embryos similar to retinoids. Therefore, we investigated alterations in the morphogenesis of murine embryos after triamcinolone acetonide (TAC) administration. TAC was administered in a single dose (15 mg/kg or 30 mg/kg body weight) to pregnant ICR-SLC mice on embryonic day 7 (E7), 8, 9, and 10. They were sacrificed on E18, and fetuses were examined for internal and external malformations. Randomly chosen fetuses were embedded in paraffin for immunohistochemical staining of the glucocorticoid receptor (GR). The groups given 15 mg/kg TAC had one peak in the incidence of cleft palate on E9 (100 %) and the groups given 30 mg/kg TAC showed a biphasic pattern in the incidence of cleft palate on E7 and E10. No other anomalies were found. GR expression was marked in the subepithelial layer of palatal processes in the treated specimens. The group given 15 mg/kg TAC on E9 provided a good model of cleft palate in ICR-SLC mice, and cleft palate was probably induced by various factors including disturbance of the bone morphogenetic protein (BMP) signaling pathway, shown by GR overexpression.

Persistent expression of Pax3 in the neural crest causes cleft palate and defective osteogenesis in mice

Transcription factors regulate tissue patterning and cell fate determination during development; however, expression of early regulators frequently abates upon differentiation, suggesting that they may also play a role in maintaining an undifferentiated phenotype. The transcription factor paired box 3 (Pax3) is expressed by multipotent neural crest precursors and is implicated in neural crest disorders in humans such as Waardenburg syndrome. Pax3 is required for development of multiple neural crest lineages and for activation of lineage-specific programs, yet expression is generally extinguished once neural crest cells migrate from the dorsal neural tube and differentiate. Using a murine Cre-inducible system, we asked whether persistent Pax3 expression in neural crest derivatives would affect development or patterning. We found that persistent expression of Pax3 in cranial neural crest cells resulted in cleft palate, ocular defects, malformation of the sphenoid bone, and perinatal lethality. Furthermore, we demonstrated that Pax3 directly regulates expression of Sostdc1, a soluble inhibitor of bone morphogenetic protein (BMP) signaling. Persistent Pax3 expression renders the cranial crest resistant to BMP-induced osteogenesis. Thus, one mechanism by which Pax3 maintains the undifferentiated state of neural crest mesenchyme may be to block responsiveness to differentiation signals from the environment. These studies provide in vivo evidence for the importance of Pax3 downregulation during differentiation of multipotent neural crest precursors and cranial development.

Tissue‐specific requirement for TGF‐β signaling during craniofacial development

Members of the transforming growth factor‐β (TGF‐β) superfamily mediate a wide range of biological activities, including cell proliferation, differentiation, extracellular matrix formation, and induction of homeobox genes, suggesting that TGF‐β signaling is important in pattern formation and organogenesis. During craniofacial development, TGF‐β is expressed in the craniofacial epithelium and the cranial neural crest (CNC) derived mesenchyme, suggesting tissue‐specific functions in regulating craniofacial development. To investigate the tissue‐specific requirement of TGF‐β signaling, we generated animal models with epithelim or CNC‐derived mesenchyme specific inactivation of Tgfbr2 gene and investigated the molecular mechanism of TGF‐β signaling in regulating the fate of craniofacial epithelial or the CNC mesenchyme cells, respectively. Using mice with conditional inactivation of Tgfbr2 in the epithelium, we show that TGF‐β signaling is specifically required for regulating palate fusion and skin development. At the cellular level, TGF‐β signaling is critical for mediating apoptosis of MEE cells during palatal fusion. On the other hand, conditional Tgfbr2 gene ablation in the CNC resulted in complete cleft secondary palate, calvaria agenesis, and other skull defects with complete phenotype penetrance. Significantly, disruption of the TGF‐β 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 TGF‐β IIR plays a critical, cell autonomous role in regulating the fate of MEE and CNC cells during palatogenesis. To explore the molecular mechanism of TGF‐β signaling in regulating craniofacial development, we analyzed downstream target genes affected by altered TGF‐β signaling in either the epithelium or the CNC‐derived mesenchyme. Comprehensive analysis reveals specific TGF‐β signaling network in regulating craniofacial development. Collectively, our study demonstrates that TGF‐β signaling plays an essential role in cell fate determination of the craniofacial epithelium and the CNC‐derived mesenchyme and provides a model for the study of abnormal craniofacial development.