Tgf-beta-mediated FasL-Fas-Caspase pathway is crucial during palatogenesis

FasL impacts Tgfb signaling in osteoblastic cells

Fas ligand (FasL, CD178) belongs to classical apoptotic molecules, however, recent evidence expands the spectrum of FasL functions into non-apoptotic processes which also applies for the bone. Tgfb subfamily members (Tgfb1, Tgfb2, Tgfb3) represent major components in osteogenic pathways and extracellular matrix. Their possible association with FasL has not yet been investigated but can be postulated. To test such a hypothesis, FasL deficient (gld) calvaria-derived cells were examined with a focus on the expression of Tgfb receptor ligands. The qPCR analysis revealed significantly increased expression of Tgfb1, Tgfb2 and Tgfb3 in gld cells. To check the vice versa effect, the gld cells were stimulated by soluble FasL. As a consequence, a dramatic decrease in expression levels of all three ligands was observed. This phenomenon was also confirmed in IDG-SW3 (osteoblastic cells of endochondral origin). TFLink gateway identified Fosl2 as an exclusive candidate of FasL capable to impact expression of all three Tgfb ligands. However, Fosl2 siRNA did not cause any significant changes in expression of Tgfb ligands. Therefore, the upregulation of the three ligands is likely to occur separately. In this respect, we tested the only exclusive candidate transcription factor for Tgfb3, Prrx1. Additionally, an overlapping candidate for Tgfb1 and Tgfb2, Mef2c capable to modulate expression of sclerostin, was examined. Prrx1 as well as Mef2c were found upregulated in gld samples and their expression decreased after addition of FasL. The same effect of FasL treatment was observed in the IDG-SW3 model. Taken together, FasL deficiency causes an increase in the expression of Tgfb ligands and stimulation by FasL reduces Tgfb expression in osteoblastic cells. The candidates mediating the effect comprise Prrx1 for Tgfb3 and Mef2c for Tgfb1/2. These results indicate FasL as a novel cytokine interfering with Tgfb signaling and thus the complex osteogenic network. The emerging non-apoptotic functions of FasL in bone development and maintenance should also be considered in treatment strategies such as the anti-osteoporotic factor.

Rab25 is involved in hypospadias via the β1 integrin/EGFR pathway

BACKGROUND

Hypospadias is a common congenital abnormality of the penile. Abnormal regulation of critical genes involved in urethral development leads to hypospadias. We used the Rab25-/- mice and foreskin fibroblasts transfected with lentivirus in vitro and in vivo to investigate the role of Rab25 in hypospadias.

METHODS

The expression levels of various molecules in tissue samples and foreskin fibroblasts were confirmed using molecular biology methods (western blotting, PCR, immunohistochemistry, etc.). A scanning electron microscope (SEM) was used to visualize the external morphology of genital tubercles (GTs) of gestation day (GD) 18.5 male wild-type (WT) and Rab25-/- mice.

RESULTS

An expanded distal cleft and V-shaped urethral opening were observed in GD 18.5 Rab25-/- mice. We demonstrated that Rab25 mediated hypospadias through the β1 integrin/EGFR pathway. In addition, silencing Rab25 inhibited cell proliferation and migration and promoted apoptosis in the foreskin fibroblasts; Ki-67- and TUNEL-positive cells were mainly concentrated near the urethral seam.

CONCLUSION

These findings suggest that Rab25 plays an essential role in hypospadias by activation of β1 integrin/EGFR pathway, and Rab25 is a critical mediator of urethral seam formation in GD18.5 male fetal mice.

Genetic Variants in Mammalian STE20-like Protein Kinase 2 were associated with risk of NSCL/P

AIM

Mammalian STE20-like protein kinase 2 (MST2) plays an important role in apoptosis and the development of many disorders. Here, we aim to explore if genetic variants in MST2 are associated with the risk of non-syndromic cleft lip with or without palate (NSCL/P).

MATERIALS AND METHODS

The association study was performed in a two-stage study of 1,069 cases and 1,724 controls to evaluate the association between genetic variants in the MST2 and NSCL/P risk. The potential function of the candidate single nucleotide polymorphism (SNP) was predicted using HaploReg, RegulomeDB, and public craniofacial histone chromatin immunoprecipitation sequencing (ChIP-seq) data. Haploview was used to perform the haplotype of risk alleles. The expression quantitative trait loci (eQTL) effect was assessed using the Genotype-Tissue Expression (GTEx) project. Gene expression in mouse embryo tissue was performed using data downloaded from GSE67985. The potential role of candidate gene in the development of NSCL/P was assessed by correlation and enrichment analysis.

RESULTS

Among SNPs in MST2, rs2922070 C allele (P_meta = 2.93E-04) and rs6988087 T allele (P_meta = 1.57E-03) were linked with significantly increased risk of NSCL/P. Rs2922070, rs6988087 and their high linkage disequilibrium (LD) SNPs constituted a risk haplotype of NSCL/P. Individuals carrying 3-4 risk alleles had an elevated risk of NSCL/P compared to those who carried less risk alleles (P = 2.00E-04). The eQTL analysis revealed a significant association between these two variants and MST2 in muscle tissue of the body. The MST2 expressed during mouse craniofacial development and over-expressed in the human orbicularis oris muscle (OOM) of NSCL/P patients compared to controls. MST2 was involved in the development of NSCL/P by regulating the mRNA surveillance pathway, the MAPK signaling pathway, the neurotrophin signaling pathway, the FoxO signaling pathway and the VEGF signaling pathway.

CONCLUSION

MST2 was associated with the development of NSCL/P.

Zonisamide improves Fas/FasL-mediated apoptosis and inflammation in a degenerative cervical myelopathy rat model

Degenerative cervical myelopathy (DCM) is a severe condition of the spinal cord caused by chronic compression. However, no studies to date have examined the effects of zonisamide (ZNS) on DCM via the Fas/FasL-mediated pathway. The aim of this study was to investigate the effects of ZNS on a DCM rat model and to explore the potential mechanisms. First, 40 adult Sprague-Dawley rats were used to establish the DCM rat model and were individually divided into four groups: the Sham group, DCM model group (DCM), ZNS group (DCM model rats treated with ZNS, 30 mg/kg/day), and ZNS + CD95 group (DCM model rats treated with ZNS and CD95). Histopathology injury and cell apoptosis, Fas and Fas ligand (FasL) expression and Fas/FasL relative protein levels were detected by hematoxylin and eosin staining, TUNEL assay, and immunofluorescence and western blotting, respectively. The results of our study demonstrated that ZNS could promote motor recovery while reversing histopathological injury and cell apoptosis in DCM rats. Moreover, Iba-1, Fas and FasL expression in DCM rats was decreased, accompanied by a decrease in cleaved caspase-3/caspase-3, cleaved caspase-8/caspase-8, cleaved caspase-9/caspase-9, cleaved caspase-10/caspase-10 and B-cell lymphoma-2 (Bcl-2)/Bcl-2 associated X (Bax) levels. All these results revealed that ZNS attenuates DCM injury in a rat model via the regulation of Fas and FasL signaling. Our study indicated that ZNS had beneficial effects on DCM and thus provided a novel theoretical approach for subsequent academic and clinical research on DCM injury.

FasL is a catabolic factor in alveolar bone homeostasis

AIM

Fas ligand (FasL) belongs to the tumour necrosis factor superfamily regulating bone turnover, inflammation, and apoptosis. The appendicular and axial skeleton phenotype of mature Faslgld mice has been reported. The impact of FasL on the alveolar bone providing support for the teeth at mature stages under healthy and induced inflammatory conditions remains unknown.

MATERIALS AND METHODS

We performed a phenotypical analysis of mice carrying the homozygous Faslgld mutation and wild-type (WT) mice (C57BL/6) under healthy conditions and upon ligature-induced periodontitis. After 12 days, micro-computed tomography analysis revealed the distance between the cement enamel junction and the alveolar bone crest. Additional structural parameters, such as the bone volume fraction (BV/TV) and the periodontal ligament space volume, were measured. Histological analyses were performed to visualize the catabolic changes at the defect site.

RESULTS

Healthy Faslgld mice were found to have more periodontal bone than their WT littermates. Faslgld had no significant effect on inflammatory osteolysis compared to WT controls with ligatures. Histology revealed eroded surfaces at the root and in the inter-proximal bone in both strains.

CONCLUSIONS

Our findings suggest that FasL is a catabolic factor in alveolar bone homeostasis but it does not affect the inflammatory osteolysis.

Making the head: Caspases in life and death

The term apoptosis, as a way of programmed cell death, was coined a half century ago and since its discovery the process has been extensively investigated. The anatomy and physiology of the head are complex and thus apoptosis has mostly been followed in separate structures, tissues or cell types. This review aims to provide a comprehensive overview of recent knowledge concerning apoptosis-related molecules involved in the development of structures of head with a particular focus on caspases, cysteine proteases having a key position in apoptotic pathways. Since many classical apoptosis-related molecules, including caspases, are emerging in several non-apoptotic processes, these were also considered. The largest organ of the head region is the brain and its development has been extensively investigated, including the roles of apoptosis and related molecules. Neurogenesis research also includes sensory organs such as the eye and ear, efferent nervous system and associated muscles and glands. Caspases have been also associated with normal function of the skin and hair follicles. Regarding mineralised tissues within craniofacial morphogenesis, apoptosis in bones has been of interest along with palate fusion and tooth development. Finally, the role of apoptosis and caspases in angiogenesis, necessary for any tissue/organ development and maintenance/homeostasis, are discussed. Additionally, this review points to abnormalities of development resulting from improper expression/activation of apoptosis-related molecules.

Spatiotemporal Expression and Functional Analysis of miRNA-22 in the Developing Secondary Palate

OBJECTIVE

Normal development of the embryonic orofacial region requires precise spatiotemporal coordination between numerous genes. MicroRNAs represent small, single-stranded, non-coding molecules that regulate gene expression. This study examines the role of microRNA-22 (miR-22) in murine orofacial ontogeny.

METHODS

Spatiotemporal and differential expression of miR-22 (mmu-miR-22-3p) within the developing secondary palate was determined by in situ hybridization and quantitative real-time PCR, respectively. Bioinformatic approaches were used to predict potential mRNA targets of miR-22 and analyze their association with cellular functions indispensable for normal orofacial ontogeny. An in vitro palate organ culture system was used to assess the role of miR-22 in secondary palate development.

RESULTS

There was a progressive increase in miR-22 expression from GD12.5 to GD14.5 in palatal processes. On GD12.5 and GD13.5, miR-22 was expressed in the future oral, nasal, and medial edge epithelia. On GD14.5, miR-22 expression was observed in the residual midline epithelial seam (MES), the nasal epithelium and the mesenchyme, but not in the oral epithelium. Inhibition of miR-22 activity in palate organ cultures resulted in failure of MES removal. Bioinformatic analyses revealed potential mRNA targets of miR-22 that may play significant roles in regulating apoptosis, migration, and/or convergence/extrusion, developmental processes that modulate MES removal during palatogenesis.

CONCLUSIONS

Results from the current study suggest a key role for miR-22 in the removal of the MES during palatogenesis and that miR-22 may represent a potential contributor to the etiology of cleft palate.

Brazilian Multiethnic Association Study of Genetic Variant Interactions among FOS, CASP8, MMP2 and CRISPLD2 in the Risk of Nonsyndromic Cleft Lip with or without Cleft Palate

Associations of CRISPLD2 (cysteine-rich secretory protein LCCL domain containing 2) and genes belonging to its activation pathway, including FOS (Fos proto-oncogene), CASP8 (caspase 8) and MMP2 (matrix metalloproteinase 2), with nonsyndromic orofacial cleft risk, have been reported, but the results are yet unclear. The aim of this study was to evaluate single nucleotide polymorphisms (SNPs) in FOS, CASP8 and MMP2 and to determine their SNP-SNP interactions with CRISPLD2 variants in the risk of nonsyndromic cleft lip with or without cleft palate (NSCL±P) in the Brazilian population. The SNPs rs1046117 (FOS), rs3769825 (CASP8) and rs243836 (MMP2) were genotyped using TaqMan allelic discrimination assays in a case-control sample containing 801 NSCL±P patients (233 nonsyndromic cleft lip only (NSCLO) and 568 nonsyndromic cleft lip and palate (NSCLP)) and 881 healthy controls via logistic regression analysis adjusted for the effects of sex and genomic ancestry proportions with a multiple comparison p value set at ≤0.01. SNP-SNP interactions with rs1546124, rs8061351, rs2326398 and rs4783099 in CRISPLD2 were performed with the model-based multifactor dimensionality reduction test complemented with a 1000 permutation-based strategy. Although the association between FOS rs1046117 and risk of NSCL±P reached only nominal p values, NSCLO risk was significantly higher in carriers of the FOS rs1046117 C allele (OR: 1.28, 95% CI: 1.10-1.64, p = 0.004), TC heterozygous genotype (OR: 1.59, 95% CI: 1.16-2.18, p = 0.003), and in the dominant model (OR: 1.50, 95% CI: 1.10-2.02, p = 0.007). Individually, no significant associations between cleft risk and the SNPs in CASP8 and MMP2 were observed. SNP-SNP interactions involving CRISPLD2 variants and rs1046117 (FOS), rs3769825 (CASP8) and rs243836 (MMP2) yielded several significant p values, mostly driven by FOS rs1046117 and CASP8 rs3769825 in NSCL±P, FOS rs1046117 in NSCLO and CRISPLD2 rs8061351 in NSCLP. Our study is the first in the Brazilian population to reveal the association of FOS rs1046117 with NSCLO risk, and to support that CRISPLD2, CASP8, FOS and MMP2 interactions may be related to the pathogenesis of this common craniofacial malformation.

Chloroquine regulates the proliferation and apoptosis of palate development on mice embryo by activating P53 through blocking autophagy in vitro

Cleft lip and palate is one of the most frequent congenital developmental defects. Autophagy is a highly conserved process of cell self-degradation in eukaryotes, involving multiple biological processes in which chloroquine (CQ) is the most common inhibitor. However, whether CQ affects and how it affects palate development is unknown. Mouse embryonic palatal cells (MEPCs) were treated with CQ to observe cell viability, apoptosis, migration, osteogenic differentiation by cell proliferation assay, flow cytometric analysis, scratch assay, and alizarin red staining. PI staining was used to measure cell cycle distribution. Immunofluorescence (IF) assay and transmission electron microscopy were used to detect autophagosomes. The autophagy-related factors (LC3 and P62), apoptosis-related markers (P53, caspase-3 cleaved caspase-3, BAX, and BCL-2), and cell cycle-related proteins (P21, CDK2, CDK4, cyclin D1, and cyclin E) were all measured by western blot. CQ inhibited the proliferation of MEPCs by arresting the G0/G1 phase of the cell cycle in a concentration- and time-dependent manner with cell cycle-related proteins P21 upregulated and CDK2, CDK4, cyclin D1, and cyclin E downregulated. Then we detected CQ also induced cell apoptosis in a dose-dependent manner by decreasing the BCL-2/BAX ratio and increasing cleaved caspase-3. Next, it was investigated that migration and osteogenesis of MEPCs decreased with CQ treatment in a dose-dependent manner. Meanwhile, CQ blocked the autophagy pathway by upregulating LC3II and P62 expressions which activated the P53 pathway. CQ activates P53 which affects MEPC biological characteristics by changing the proliferation and apoptosis of MEPCs through inhibiting autophagy.

A unique form of collective epithelial migration is crucial for tissue fusion in the secondary palate and can overcome loss of epithelial apoptosis

Tissue fusion frequently requires the removal of an epithelium that intervenes distinct primordia to form one continuous structure. In the mammalian secondary palate, a midline epithelial seam (MES) forms between two palatal shelves and must be removed to allow mesenchymal confluence. Abundant apoptosis and cell extrusion support their importance in MES removal. However, genetically disrupting the intrinsic apoptotic regulators BAX and BAK within the MES results in complete loss of cell death and cell extrusion, but successful removal of the MES. Novel static- and live-imaging approaches reveal that the MES is removed through streaming migration of epithelial trails and islands to reach the oral and nasal epithelial surfaces. Epithelial trail cells that express the basal epithelial marker ΔNp63 begin to express periderm markers, suggesting that migration is concomitant with differentiation. Live imaging reveals anisotropic actomyosin contractility within epithelial trails, and genetic ablation of actomyosin contractility results in dispersion of epithelial collectives and failure of normal MES migration. These findings demonstrate redundancy between cellular mechanisms of morphogenesis, and reveal a crucial and unique form of collective epithelial migration during tissue fusion.

Summary: Multiple cellular processes mediate secondary palate fusion, including a unique form of streaming collective epithelial migration driven by pulsatile actomyosin contractility.

Influence of bone formation by composite scaffolds with different proportions of hydroxyapatite and collagen

Composite scaffolds with different proportions of hydroxyapatite (HA) and collagen (COL) produced different bone induction results.

OBJECTIVE

To examine the composite scaffolds with optimal proportion of HA and COL to achieve earlier bone induction and maximum bone formation.

METHODS

Composite scaffolds with the HA/COL weight ratio of 7:3, 3:7, 5:5 and 9:1 were prepared, as HA powder was added to collagen solution at 130℃ for 48 h. Then, the composites with different proportions of HA/COL were implanted into the extraction socket of right upper central incisor of C57BL/6 J mice. The bone formation of the extraction socket was observed by Hematoxylin-eosin (HE) and Masson-trichrome (Masson) staining at 1 and 2 weeks after operation. Five weeks later, the bone formation of extraction socket was observed by micro computed tomography (micro-CT). After MC3T3-E1 cells were co-cultured with materials of different proportions for 3 days, the number of cells attached on the surface of the materials and entering the materials were counted, and the expression of osteogenic related genes (Runx2, Ocn. Osx and Alp) was detected by reverse transcription polymerase chain reaction (RT-PCR). The composite scaffolds with different proportion of HA/COL with and without mouse bone marrow mesenchymal stem cells (BMMSCs) were implanted into the back of adult mice and cultured subcutaneously for 30 days, and observed histologically by HE and Masson staining.

RESULTS

After one week implantation with the composite HA/COL scaffolds with the weight ratio of 7:3, 3:7, 5:5 and 9:1, there was no new bone formation in the extraction socket in mouse. However, two weeks later, new bone was firstly observed in the tooth socket with the composite HA/COL scaffolds of 7:3. 5 weeks later, micro-CT scanning showed that the total amount of newly formed bone, trabecular width and bone mineral density of the HA/COL scaffolds of 7:3 were higher than the other HA/COL scaffolds (P < 0.05). After MC3T3-E1 cells were co-cultured with different composite HA/COL scaffolds for 3 days. The number of cells on the surface and inside of the HA/COL scaffolds of 7:3 was more than the other materials, and the difference was statistically significant (P < 0.05). The expression levels of Ocn and Osx of MC3T3-E1 cells were also the highest in the HA/COL scaffolds of 7:3 (P < 0.01). Bone formation was observed in the composite HA/COL scaffold of 7:3 with BMMSCs subcutaneously in mouse for 30 days, while only osteoid formation was observed in the same scaffold without BMMSCs. but bone formation was not detected in the other proportions of the HA/COL scaffolds.

SIGNIFICANCE

Compared with other proportions of HA/COL, the composite HA/COL scaffolds of 7:3 has stronger ability to promote bone formation, recruit osteoblasts to attach and enter into the scaffolds, and promote the osteogenesis of BMMSCs.

The cleft palate candidate gene BAG6 supports FoxO1 acetylation to promote FasL-mediated apoptosis during palate fusion

BACKGROUND

Cleft palate is a common craniofacial defect, which occurs when the palate fails to fuse during development. During fusion, the palatal shelves migrate towards the embryonic midline to form a seam. Apoptotic elimination of medial edge epithelium (MEE) cells along this seam is required for the completion of palate fusion.

METHODS

Whole exome sequencing (WES) of six Chinese cleft palate families was applied to identify novel cleft palate-associated gene variants. Palatal fusion and immunofluorescence studies were performed in a murine palatal shelf organ culture model. Gene and protein expression were analyzed by qPCR and immunoblotting in murine MEE cells during seam formation in vivo. Mechanistic immunoprecipitation studies were performed in murine MEE cells in vitro.

RESULTS

WES identified Bcl-2 associated anthanogene 6 (BAG6) as a novel cleft palate-associated gene. In murine MEE cells, we discovered upregulation of Bag6 and the transcription factor forkhead box protein O1 (FoxO1) during seam formation in vivo. Using a palatal shelf organ culture model, we demonstrate that nuclear-localized Bag6 enhances MEE cell apoptosis by promoting p300's acetylation of FoxO1, thereby promoting transcription of the pro-apoptotic Fas ligand (FasL). Subsequent gain- and loss-of-function studies in the organ culture model demonstrated that FasL is required for Bag6/acFoxO1-mediated activation of pro-apoptotic Bax/caspase-3 signaling, MEE apoptosis, and palate fusion. Palatal shelf contact was shown to enhance Bag6 nuclear localization and upregulate nuclear acFoxO1 in MEE cells.

CONCLUSIONS

These findings demonstrate that nuclear-localized Bag6 and p300 co-operatively enhance FoxO1 acetylation to promote FasL-mediated MEE apoptosis during palate fusion.

IRF6 and TAK1 coordinately promote the activation of HIPK2 to stimulate apoptosis during palate fusion

Cleft palate is a common craniofacial defect caused by a failure in palate fusion. The palatal shelves migrate toward one another and meet at the embryonic midline, creating a seam. Transforming growth factor–β3 (TGF-β3)–induced apoptosis of the medial edge epithelium (MEE), the cells located along the seam, is required for completion of palate fusion. The transcription factor interferon regulatory factor 6 (IRF6) promotes TGF-β3–induced MEE cell apoptosis by stimulating the degradation of the transcription factor ΔNp63 and promoting the expression of the gene encoding the cyclin-dependent kinase inhibitor p21. Because homeodomain-interacting protein kinase 2 (HIPK2) functions downstream of IRF6 in human cancer cells and is required for ΔNp63 protein degradation in keratinocytes, we investigated whether HIPK2 played a role in IRF6-induced ΔNp63 degradation in palate fusion. HIPK2 was present in the MEE cells of mouse palatal shelves during seam formation in vivo, and ectopic expression of IRF6 in palatal shelves cultured ex vivo stimulated the expression of Hipk2 and the accumulation of phosphorylated HIPK2. Knockdown and ectopic expression experiments in organ culture demonstrated that p21 was required for HIPK2- and IRF6-dependent activation of caspase 3, MEE apoptosis, and palate fusion. Contact between palatal shelves enhanced the phosphorylation of TGF-β–activated kinase 1 (TAK1), which promoted the phosphorylation of HIPK2 and palate fusion. Our findings demonstrate that HIPK2 promotes seam cell apoptosis and palate fusion downstream of IRF6 and that IRF6 and TAK1 appear to coordinately enhance the abundance and activation of HIPK2 during palate fusion.

TGF-β Signaling and the Epithelial-Mesenchymal Transition during Palatal Fusion

Signaling by transforming growth factor (TGF)-β plays an important role in development, including in palatogenesis. The dynamic morphological process of palatal fusion occurs to achieve separation of the nasal and oral cavities. Critically and specifically important in palatal fusion are the medial edge epithelial (MEE) cells, which are initially present at the palatal midline seam and over the course of the palate fusion process are lost from the seam, due to cell migration, epithelial-mesenchymal transition (EMT), and/or programed cell death. In order to define the role of TGF-β signaling during this process, several approaches have been utilized, including a small interfering RNA (siRNA) strategy targeting TGF-β receptors in an organ culture context, the use of genetically engineered mice, such as Wnt1-cre/R26R double transgenic mice, and a cell fate tracing through utilization of cell lineage markers. These approaches have permitted investigators to distinguish some specific traits of well-defined cell populations throughout the palatogenic events. In this paper, we summarize the current understanding on the role of TGF-β signaling, and specifically its association with MEE cell fate during palatal fusion. TGF-β is highly regulated both temporally and spatially, with TGF-β3 and Smad2 being the preferentially expressed signaling molecules in the critical cells of the fusion processes. Interestingly, the accessory receptor, TGF-β type 3 receptor, is also critical for palatal fusion, with evidence for its significance provided by Cre-lox systems and siRNA approaches. This suggests the high demand of ligand for this fine-tuned signaling process. We discuss the new insights in the fate of MEE cells in the midline epithelial seam (MES) during the palate fusion process, with a particular focus on the role of TGF-β signaling.

Glycoprotein A repetitions predominant (GARP) positively regulates transforming growth factor (TGF) β3 and is essential for mouse palatogenesis

Glycoprotein A repetitions predominant (GARP) (encoded by the Lrrc32 gene) plays important roles in cell-surface docking and activation of TGFβ. However, GARP's role in organ development in mammalian systems is unclear. To determine the function of GARP in vivo, we generated a GARP KO mouse model. Unexpectedly, the GARP KO mice died within 24 h after birth and exhibited defective palatogenesis without apparent abnormalities in other major organs. Furthermore, we observed decreased apoptosis and SMAD2 phosphorylation in the medial edge epithelial cells of the palatal shelf of GARP KO embryos at embryonic day 14.5 (E14.5), indicating a defect in the TGFβ signaling pathway in the GARP-null developing palates. Of note, the failure to develop the secondary palate and concurrent reduction of SMAD phosphorylation without other defects in GARP KO mice phenocopied TGFβ3 KO mice, although GARP has not been suggested previously to interact with TGFβ3. We found that GARP and TGFβ3 co-localize in medial edge epithelial cells at E14.5. In vitro studies confirmed that GARP and TGFβ3 directly interact and that GARP is indispensable for the surface expression of membrane-associated latent TGFβ3. Our findings indicate that GARP is essential for normal morphogenesis of the palate and demonstrate that GARP plays a crucial role in regulating TGFβ3 signaling during embryogenesis. In conclusion, we have uncovered a novel function of GARP in positively regulating TGFβ3 activation and function.

Crispld2 is required for neural crest cell migration and cell viability during zebrafish craniofacial development

The CAP superfamily member, CRISPLD2, has previously been shown to be associated with nonsyndromic cleft lip and palate (NSCLP) in human populations and to be essential for normal craniofacial development in the zebrafish. Additionally, in rodent models, CRISPLD2 has been shown to play a role in normal lung and kidney development. However, the specific role of CRISPLD2 during these developmental processes has yet to be determined. In this study, it was demonstrated that Crispld2 protein localizes to the orofacial region of the zebrafish embryo and knockdown of crispld2 resulted in abnormal migration of neural crest cells (NCCs) during both early and late time points. An increase in cell death after crispld2 knockdown as well as an increase in apoptotic marker genes was also shown. This data suggests that Crispld2 modulates the migration, differentiation, and/or survival of NCCs during early craniofacial development. These results indicate an important role for Crispld2 in NCC migration during craniofacial development and suggests involvement of Crispld2 in cell viability during formation of the orofacies.

IRF6 is the mediator of TGFβ3 during regulation of the epithelial mesenchymal transition and palatal fusion

Mutation in interferon regulatory factor 6 (IRF6) is known to cause syndromic and non-syndromic cleft lip/palate in human. In this study, we investigated the molecular mechanisms related to IRF6 during palatal fusion using palatal shelves organ culture. The results showed that ablation of Irf6 resulted in a delay in TGFβ3-regulated palatal fusion. Ectopic expression of IRF6 was able to promote palatal fusion and rescue shTgfβ3-induced fusion defect. These findings indicate that IRF6 is involved in TGFβ3-mediated palatal fusion. Molecular analysis revealed that ectopic expression of IRF6 increased the expression of SNAI2, an epithelial mesenchymal transition (EMT) regulator, and diminished the expression of various epithelial markers, such as E-cadherin, Plakophilin and ZO-1. In addition, knockdown of Irf6 expression decreased SNAI2 expression, and restored the expression of ZO-1 and Plakophilin that were diminished by TGFβ3. Blocking of Snai2 expression delayed palatal fusion and abolished the IRF6 rescuing effect associated with shTgfβ3-induced fusion defect. These findings indicate that TGFβ3 increases IRF6 expression and subsequently regulates SNAI2 expression, and IRF6 appears to regulate EMT during palatal fusion via SNAI2. Taken together, this study demonstrates that IRF6 is a mediator of TGFβ3, which regulates EMT and fusion process during the embryonic palate development.

Bmp2 and Bmp4 accelerate alveolar bone development

Alveolar bone remodeling is a continuous process that takes place during development and in response to various physiological and pathological stimuli. However, detailed knowledge regarding the underlying mechanisms involved in alveolar bone development is still lacking. This study aims at improving our understanding of alveolar bone formation and the role of bone morphogenetic proteins (Bmps) in this process. Mice at embryonic (E) day 13.5 to postnatal (PN) day 15.5 were selected to observe the process of alveolar bone development. Alveolar bone development was found to be morphologically observable at E14.5. Molar teeth isolated from mice at PN7.5 were pretreated with Bmp2, Bmp4, Noggin, or BSA, and grafted subcutaneously into mice. The subcutaneously implanted tooth germs formed alveolar bone indicating the role of the dental follicle in alveolar bone development. Alveolar bone formation was increased after pretreatment with Bmp2 and Bmp4, but not with Noggin. Gene expression levels in dental follicle cells from murine molars were also determined by real-time RT-PCR. The expression levels of Runx2, Bsp, and Ocn were significantly higher in dental follicle cells cultured with Bmp2 or Bmp4, and significantly lower in those cultured with Noggin when compared with that of the BSA controls. Our results suggest that the dental follicle participates in alveolar bone formation and Bmp2/4 appears to accelerate alveolar bone development.

Role of angiogenesis-related genes in cleft lip/palate: review of the literature

OBJECTIVES

Cleft lip and cleft palate (CLP) are the most common congenital craniofacial anomalies. They have a multifactorial etiology and result from an incomplete fusion of the facial buds. Two main mechanisms, acting alone or interacting with each other, were evidenced in this fusion defect responsible for CLP: defective tissue development and/or defective apoptosis in normal or defective tissues. The objective of this work was to study the implication and role of angiogenesis-related genes in the etiology of CL/P.

METHODS

Our methodological approach included a systematic and thorough analysis of the genes involved in CL/P (syndromic and non-syndromic forms) including previously identified genes but also genes that could potentially be angiogenesis-related (OMIM, Pub Med).We studied the interactions of these different genes and their relationships with potential environmental factors.

RESULTS

TGFβ, FGA, PDGFc, PDGFRa, FGF, FGFR1, FGFR2 growth factors as well as MMP and TIMP2 proteolytic enzymes are involved in the genesis of CLP (P>L). Furthermore, 18 genes involved in CLP also interact with angiogenesis-related genes.

DISCUSSION

Even if the main angiogenesis-related genes involved in CLP formation are genes participating in several biological activities and their implication might not be always related to angiogenesis defects, they nevertheless remain an undeniably important research pathway. Furthermore, their interactions with environmental factors make them good candidates in the field of CLP prevention.

Transcriptome profiling of CTLs regulated by rapamycin using RNA-Seq

Memory programming of cytotoxic T cells (CTLs) by inflammatory cytokines can be regulated by mammalian target of rapamycin (mTOR). We have shown that inhibition of mTOR during CTL activation leads to the enhancement of memory, but the molecular mechanisms remain largely unknown. Using high-throughput RNA-Seq, we identified genes and functions in mouse CTLs affected by mTOR inhibition through rapamycin. Of the 43,221 identified transcripts, 184 transcripts were differentially expressed after rapamycin treatment, corresponding to 128 annotated genes. Of these genes, 114 were downregulated and only 14 were upregulated. Most importantly, 50 of them are directly related to cell death and survival. In addition, several genes such as CD62L are related to migration. Furthermore, we predicted downregulation of transcriptional regulators based on the total differentially expressed genes, as well as the subset of apoptosis-related genes. Quantitative PCR confirmed the differential expressions detected in RNA-Seq. We conclude that the regulatory function of rapamycin may work through inhibition of multiple genes related to apoptosis and migration, which enhance CTL survival into memory.

Multiple tissue-specific requirements for the BMP antagonist Noggin in development of the mammalian craniofacial skeleton

Proper morphogenesis is essential for both form and function of the mammalian craniofacial skeleton, which consists of more than twenty small cartilages and bones. Skeletal elements that support the oral cavity are derived from cranial neural crest cells (NCCs) that develop in the maxillary and mandibular buds of pharyngeal arch 1 (PA1). Bone Morphogenetic Protein (BMP) signaling has been implicated in most aspects of craniofacial skeletogenesis, including PA1 development. However, the roles of the BMP antagonist Noggin in formation of the craniofacial skeleton remain unclear, in part because of its multiple domains of expression during formative stages. Here we used a tissue-specific gene ablation approach to assess roles of Noggin (Nog) in two different tissue domains potentially relevant to mandibular and maxillary development. We found that the axial midline domain of Nog expression is critical to promote PA1 development in early stages, necessary for adequate outgrowth of the mandibular bud. Subsequently, Nog expression in NCCs regulates craniofacial cartilage and bone formation. Mice lacking Nog in NCCs have an enlarged mandible that results from increased cell proliferation in and around Meckel׳s cartilage. These mutants also show complete secondary cleft palate, most likely due to inhibition of posterior palatal shelf elevation by disrupted morphology of the developing skull base. Our findings demonstrate multiple roles of Noggin in different domains for craniofacial skeletogenesis, and suggest an indirect mechanism for secondary cleft palate in Nog mutants that may be relevant to human cleft palate as well.

Putative functions of extracellular matrix glycoproteins in secondary palate morphogenesis

Cleft palate is a common birth defect in humans. Elevation and fusion of paired palatal shelves are coordinated by growth and transcription factors, and mutations in these can cause malformations. Among the effector genes for growth factor signaling are extracellular matrix (ECM) glycoproteins. These provide substrates for cell adhesion (e.g., fibronectin, tenascins), but also regulate growth factor availability (e.g., fibrillins). Cleft palate in Bmp7 null mouse embryos is caused by a delay in palatal shelf elevation. In contrast, palatal shelves of Tgf-β3 knockout mice elevate normally, but a cleft develops due to their failure to fuse. However, nothing is known about a possible functional interaction between specific ECM proteins and Tgf-β/Bmp family members in palatogenesis. To start addressing this question, we studied the mRNA and protein distribution of relevant ECM components during secondary palate development, and compared it to growth factor expression in wildtypewild type and mutant mice. We found that fibrillin-2 (but not fibrillin-1) mRNA appeared in the mesenchyme of elevated palatal shelves adjacent to the midline epithelial cells, which were positive for Tgf-β3 mRNA. Moreover, midline epithelial cells started expressing fibronectin upon contact of the two palatal shelves. These findings support the hypothesis that fibrillin-2 and fibronectin are involved in regulating the activity of Tgf-β3 at the fusing midline. In addition, we observed that tenascin-W (but not tenascin-C) was misexpressed in palatal shelves of Bmp7-deficient mouse embryos. In contrast to tenascin-C, tenascin-W secretion was strongly induced by Bmp7 in embryonic cranial fibroblasts in vitro. These results are consistent with a putative function for tenascin-W as a target of Bmp7 signaling during palate elevation. Our results indicate that distinct ECM proteins are important for morphogenesis of the secondary palate, both as downstream effectors and as regulators of Tgf-β/Bmp activity.

Coran A, Sukhotnik I. Dietary transforming growth factor-beta 2 (TGF-β2) supplementation reduces methotrexate-induced intestinal mucosal injury in a rat

BACKGROUND/AIMS

Dietary supplementation with transforming growth factor-beta (TGF-β) has been proven to minimize intestinal damage and facilitate regeneration after mucosal injury. In the present study, we evaluated the effects of oral TGF-β2 supplementation on intestinal structural changes, enterocyte proliferation and apoptosis following methotrexate (MTX)-induced intestinal damage in a rat and in a cell culture model.

METHODS

Caco-2 cells were treated with MTX and were incubated with increasing concentrations of TGF-β2. Cell apoptosis was assessed using FACS analysis by annexin staining and cell viability was monitored using Trypan Blue assay. Male rats were divided into four experimental groups: Control rats, CONTR- TGF-β rats were treated with diet enriched with TGF-β2, MTX rats were treated with a single dose of methotrexate, and MTX- TGF-β rats were treated with diet enriched with TGF-β2. Intestinal mucosal damage, mucosal structural changes, enterocyte proliferation and enterocyte apoptosis were determined at sacrifice. Real Time PCR and Western blot were used to determine bax and bcl-2 mRNA, p-ERK, β-catenin, IL-1B and bax protein expression.

RESULTS

Treatment of MTX-pretreated Caco-2 cells with TGF-B2 resulted in increased cell viability and decreased cell apoptosis. Treatment of MTX-rats with TGF-β2 resulted in a significant increase in bowel and mucosal weight, DNA and protein content, villus-height (ileum), crypt-depth (jejunum), decreased intestinal-injury score, decreased level of apoptosis and increased cell proliferation in jejunum and ileum compared to the untreated MTX group. MTX-TGF-β2 rats demonstrated a lower bax mRNA and protein levels as well as increased bcl-2 mRNA levels in jejunum and ileum compared to MTX group. Treatment with TGF-β2 also led to increased pERK, IL-1B and β-catenin protein levels in intestinal mucosa.

CONCLUSIONS

Treatment with TGF-β2 prevents mucosal-injury, enhances p-ERK and β-catenin induced enterocyte proliferation, inhibits enterocyte apoptosis and improves intestinal recovery following MTX-induced intestinal-mucositis in rats.

Osteoclast activated FoxP3+ CD8+ T-cells suppress bone resorption in vitro

Background

Osteoclasts are the body’s sole bone resorbing cells. Cytokines produced by pro-inflammatory effector T-cells (T_EFF) increase bone resorption by osteoclasts. Prolonged exposure to the T_EFF produced cytokines leads to bone erosion diseases such as osteoporosis and rheumatoid arthritis. The crosstalk between T-cells and osteoclasts has been termed osteoimmunology. We have previously shown that under non-inflammatory conditions, murine osteoclasts can recruit naïve CD8 T-cells and activate these T-cells to induce CD25 and FoxP3 (Tc_REG). The activation of CD8 T-cells by osteoclasts also induced the cytokines IL-2, IL-6, IL-10 and IFN-γ. Individually, these cytokines can activate or suppress osteoclast resorption.

Principal Findings

To determine the net effect of Tc_REG on osteoclast activity we used a number of in vitro assays. We found that Tc_REG can potently and directly suppress bone resorption by osteoclasts. Tc_REG could suppress osteoclast differentiation and resorption by mature osteoclasts, but did not affect their survival. Additionally, we showed that Tc_REG suppress cytoskeletal reorganization in mature osteoclasts. Whereas induction of Tc_REG by osteoclasts is antigen-dependent, suppression of osteoclasts by Tc_REG does not require antigen or re-stimulation. We demonstrated that antibody blockade of IL-6, IL-10 or IFN-γ relieved suppression. The suppression did not require direct contact between the Tc_REG and osteoclasts.

Significance

We have determined that osteoclast-induced Tc_REG can suppress osteoclast activity, forming a negative feedback system. As the CD8 T-cells are activated in the absence of inflammatory signals, these observations suggest that this regulatory loop may play a role in regulating skeletal homeostasis. Our results provide the first documentation of suppression of osteoclast activity by CD8 regulatory T-cells and thus, extend the purview of osteoimmunology.