The facial neural crest controls fore- and midbrain patterning by regulating Foxg1 expression through Smad1 activity.

The facial neural crest (FNC), a pluripotent embryonic structure forming craniofacial structures, controls the activity of brain organisers and stimulates cerebrum growth. To understand how the FNC conveys its trophic effect, we have studied the role of Smad1, which encodes an intracellular transducer, to which multiple signalling pathways converge, in the regulation of Foxg1. Foxg1 is a transcription factor essential for telencephalic specification, the mutation of which leads to microcephaly and mental retardation. Smad1 silencing, based on RNA interference (RNAi), was performed in pre-migratory FNC cells. Soon after electroporation of RNAi molecules, Smad1 inactivation abolished the expression of Foxg1 in the chick telencephalon, resulting in dramatic microcephaly and partial holoprosencephaly. In addition, the depletion of Foxg1 activity altered the expression Otx2 and Foxa2 in di/mesencephalic neuroepithelium. However, when mutated forms of Smad1 mediating Fgf and Wnt signalling were transfected into FNC cells, these defects were overcome. We also show that, downstream of Smad1 activity, Dkk1, a Wnt antagonist produced by the FNC, initiated the specification of the telencephalon by regulating Foxg1 activity. Additionally, the activity of Cerberus in FNC-derived mesenchyme synergised with Dkk1 to control Foxg1 expression and maintain the balance between Otx2 and Foxa2.

Different contribution of BRINP3 gene in chronic periodontitis and peri-implantitis: a cross-sectional study.

BACKGROUND: Peri-implantitis is a chronic inflammation, resulting in loss of supporting bone around implants. Chronic periodontitis is a risk indicator for implant failure. Both diseases have a common etiology regarding inflammatory destructive response. BRINP3 gene is associated with aggressive periodontitis. However, is still unclear if chronic periodontitis and peri-implantitis have the same genetic background. The aim of this work was to investigate the association between BRINP3 genetic variation (rs1342913 and rs1935881) and expression and susceptibility to both diseases. METHODS: Periodontal and peri-implant examinations were performed in 215 subjects, divided into: healthy (without chronic periodontitis and peri-implantitis, n = 93); diseased (with chronic periodontitis and peri-implantitis, n = 52); chronic periodontitis only (n = 36), and peri-implantitis only (n = 34). A replication sample of 92 subjects who lost implants and 185 subjects successfully treated with implants were tested. DNA was extracted from buccal cells. Two genetic markers of BRINP3 (rs1342913 and rs1935881) were genotyped using TaqMan chemistry. Chi-square (p < 0.05) compared genotype and allele frequency between groups. A subset of subjects (n = 31) had gingival biopsies harvested. The BRINP3 mRNA levels were studied by CT method (2(ΔΔCT)). Mann-Whitney test correlated the levels of BRINP3 in each group (p < 0.05). RESULTS: Statistically significant association between BRINP3 rs1342913 and peri-implantitis was found in both studied groups (p = 0.04). The levels of BRINP3 mRNA were significantly higher in diseased subjects compared to healthy individuals (p = 0.01). CONCLUSION: This study provides evidence that the BRINP3 polymorphic variant rs1342913 and low level of BRINP3 expression are associated with peri-implantitis, independently from the presence of chronic periodontitis.

Cubilin, a high affinity receptor for fibroblast growth factor 8, is required for cell survival in the developing vertebrate head.

Cubilin (Cubn) is a multiligand endocytic receptor critical for the intestinal absorption of vitamin B12 and renal protein reabsorption. During mouse development, Cubn is expressed in both embryonic and extra-embryonic tissues, and Cubn gene inactivation results in early embryo lethality most likely due to the impairment of the function of extra-embryonic Cubn. Here, we focus on the developmental role of Cubn expressed in the embryonic head. We report that Cubn is a novel, interspecies-conserved Fgf receptor. Epiblast-specific inactivation of Cubn in the mouse embryo as well as Cubn silencing in the anterior head of frog or the cephalic neural crest of chick embryos show that Cubn is required during early somite stages to convey survival signals in the developing vertebrate head. Surface plasmon resonance analysis reveals that fibroblast growth factor 8 (Fgf8), a key mediator of cell survival, migration, proliferation, and patterning in the developing head, is a high affinity ligand for Cubn. Cell uptake studies show that binding to Cubn is necessary for the phosphorylation of the Fgf signaling mediators MAPK and Smad1. Although Cubn may not form stable ternary complexes with Fgf receptors (FgfRs), it acts together with and/or is necessary for optimal FgfR activity. We propose that plasma membrane binding of Fgf8, and most likely of the Fgf8 family members Fgf17 and Fgf18, to Cubn improves Fgf ligand endocytosis and availability to FgfRs, thus modulating Fgf signaling activity.

Plasma membrane cholesterol depletion disrupts prechordal plate and affects early forebrain patterning.

Cholesterol-rich membrane microdomains (CRMMs) are specialized structures that have recently gained much attention in cell biology because of their involvement in cell signaling and trafficking. However, few investigations, particularly those addressing embryonic development, have succeeded in manipulating and observing CRMMs in living cells. In this study, we performed a detailed characterization of the CRMMs lipid composition during early frog development. Our data showed that disruption of CRMMs through methyl-ß-cyclodextrin (MßCD) cholesterol depletion at the blastula stage did not affect Spemann's organizer gene expression and inductive properties, but impaired correct head development in frog and chick embryos by affecting the prechordal plate gene expression and cellular morphology. The MßCD anterior defect phenotype was recapitulated in head anlagen (HA) explant cultures. Culture of animal cap expressing Dkk1 combined with MßCD-HA generated a head containing eyes and cement gland. Together, these data show that during Xenopus blastula and gastrula stages, CRMMs have a very dynamic lipid composition and provide evidence that the secreted Wnt antagonist Dkk1 can partially rescue anterior structures in cholesterol-depleted head anlagen.

CTGF/CCN2 has a chemoattractive function but a weak adhesive property to embryonic carcinoma cells.

Connective tissue growth factor (CTGF/CCN2) is a protein of the CCN family that modulates cell-ECM interactions in a variety of cell types. In this study, we investigated the chemotactic and adhesive properties of CCN2 protein in embryonic teratocarcinoma P19 cells. Initially, P19 cells were attracted to CCN2-coated agarose beads. In Boyden chamber experiments, CCN2-containing medium induced a threefold greater migration of P19 cells. CCN2 adhesion properties were studied by using optical tweezers. The specific adhesion times of P19 cells to polystyrene beads coated with laminin, fibronectin, CCN2 and bovine serum albumin were 1.8 ± 0.5s, 2.7 ± 0.4s, 10 ± 2s and 13 ± 2s, respectively, revealing an unexpectedly low adhesive capacity of CCN2 protein for P19 cells. In conclusion, our findings support the chemoattractive role of CCN2 for P19 cells, but not its adhesive role when compared to laminin or fibronectin.

Dynamic analysis of the expression of the TGFbeta/SMAD2 pathway and CCN2/CTGF during early steps of tooth development.

BACKGROUND/AIMS: CCN2 is present during tooth development. However, the relationship between CCN2 and the transforming growth factor beta (TGFbeta)/SMAD2/3 signaling cascade during early stages of tooth development is unclear. Here, we compare the expression of CCN2 and TGFbeta/SMAD2/3 components during tooth development, and analyze the functioning of TGFbeta/SMAD2/3 in wild-type (WT) and Ccn2 null (Ccn2-/-) mice. METHODS: Coronal sections of mice on embryonic day (E)11.5, E12.5, E13.5, E14.5 and E18.5 from WT and Ccn2-/- were immunoreacted to detect CCN2 and components of the TGFbeta signaling pathway and assayed for 5'-bromo-2'-deoxyuridine immunolabeling and proliferating cell nuclear antigen immunostaining. RESULTS: CCN2 and TGFbeta signaling components such as TGFbeta1, TGFbeta receptor II, SMADs2/3 and SMAD4 were expressed in inducer tissues during early stages of tooth development. Proliferation analysis in these areas showed that epithelial cells proliferate less than mesenchymal cells from E11.5 to E13.5, while at E14.5 they proliferate more than mesenchymal cells. We did not find a correlation between functioning of the TGFbeta1 cascade and CCN2 expression because Ccn2-/- mice showed neither a reduction in SMAD2 phosphorylation nor a difference in cell proliferation. CONCLUSION: CCN2 and the TGFbeta/SMAD2/3 signaling pathway are active in signaling centers of tooth development where proliferation is dynamic, but these mechanisms may act independently.