• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.171-180
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• 2003

The development of calvarial bones is tighly co-ordinated with the growth of the brain and needs of harmonious interactions between different tissues within the calvarial sutures. Premature fusion of cranial sutures, known as craniosynostosis, presumably involves disturbance of these interactions. Mutations in the homeobox-containg gene Msx2 cause human craniosynostosis syndrome. Msx genes, which are consist of Msx1, Msx2 and Msx3, are homeobox-containg transcripton factors, and were originally identified as homologue of Drosophila msh(muscle segment homeobox) gene. Msx1 and Msx2 genes, expressed mostly in overlapping patterns at multiple site of tissue interactions during vertebrate development, are associated with epithelial-mesenchymal interactions during organogenesis, targets of BMP and FGF signaling. To elucidate the function of Msx genes in the early morphogenesis of mouse cranial suture, we analyzed the expression of them by in situ hybridization during embryonic(E15-E18) stage, and did vivo experiments in E15.5 mouse using rhBMP-2, rhFGF-2 protein soaked bead. In the sagittal suture, Msx1 was expressed in the mesenchyme of suture and the dura mater, Msx2 was intensely expressed in the sutural mesenchyme and the dura mater. In the coronal suture both of Msx genes were expressed intensely in the sutural mesenchyme and expressed in the periosteum also. Msx1 had a broader expression pattern than Msx2. BMP2 beads induced expression of both Msx1 and Msx2, FGF2 beads induced expression of Msx1, but not Msx2. Taken together, these data suggest that Msx1 and Msx2 genes have important role in regulating the morphogenesis and maintenance of embryonic cranial suture. Both of Msx genes are expressed similarly but because of their upstream signaling, they function dependently or cooperatively according to change of signaling molecule.

• The korean journal of orthodontics
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• v.38 no.2
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• pp.133-143
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• 2008

Objective: This study was performed to identify the characteristics of the MSX1 gene (locus chromosome 4p16) in Korean nonsyndromic cleft lip and palate (CL/P), which is assumed to be a major candidate gene acting as a causal factor in nonsyndromic CL/P and missing teeth. Methods: The 36 individuals (23 males and 13 females) who had visited the department of orthodontics at from 1998 to 2002 and who had nonsyndromic CL/P were included in the study. Using a PCR-based assay, the MSX1 gene was amplified, sequenced, and searched for inferred protein products (Reference: Homo sapiens MSX1, accession number AF426432 and NP_002439). The common single nucleotide polymorph isms were observed. Results: In exon 1, nucleotide "A" of the 253 basepair (bp) region was substituted for "G", and in the 255 bp region, nucleotide "G" was inserted. In exon 2, nucleotide "C" of the 11 bp region was substituted for "A", and "T" or "G" was inserted into the 351 bp region whereas "T" or "A" was inserted into the 352 bp region. In protein analysis, "Thr85Ala" missense mutation was found. The "Thr85Ala" missense mutation in this study is different from those of studies using subjects of other races. Conclusions: The results suggest that there is specific mutation of MSX1 in Korean and it plays an important role in Korean nonsyndromic CL/P. However, any distinct genetic polymorphisms between CL/P with missing teeth in the cleft region and CL/P without missing teeth could not be found.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.3
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• pp.391-405
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• 2003

Craniosynostosis, known as a premature fusion of cranial sutures, is a developmental disorder characterized by precocious differentiation and mineralization of osteoblasts in the calvarial sutures. Recent genetic studies have demonstrated that mutation in the homeobox gene Msx2 causes Boston-type human craniosynostosis. Additionally, the phenotype of Dlx5 homozygote mutant mouse presents craniofacial abnormalities including a delayed ossification of calvarial bone. Furthermore transcription of osteocalcin, a mature osteoblast marker, is reciprocally regulated by the homeodomain proteins Msx2 and Dlx5. These facts suggest important roles of osteocalcin, Msx2 and Dlx5 genes in the calvarial bone growth and suture morphogenesis. To elucidate the function of these molecules in the early morphogenesis of mouse cranial sutures, we have first analyzed by in situ hybridization the expression of osteocalcin, Msx2 and Dlx5 genes in the developing parietal bone and sagittal suture of mouse calvaria during the embryonic (E15-E18) stage. Osteocalcin mRNA was found in the periosteum of parietal bones from E15, and gradually more highly expressed with aging. Msx2 mRNA was intensely expressed in the sutural mesenchyme, osteogenic fronts and mildly expressed in the dura mater during the embryonic stage. Dlx5 mRNA was intensely expressed osteogenic fronts and the periostem of parietal bones. To further examine the upstream signaling molecules of transcription factor Msx2 and Dlx5, we have done in vitro experiments in E15.5 mouse calvarial explants. Interestingly, implantation of BMP2-, BMP4-soaked beads onto the osteogenic fronts after 48 hours organ culture induced etopic expressions of Msx2 and Dlx5 genes. On the other hand, overexpression of $TGF{\beta}1$, GDF-6, -7, FGF-2, -4 and Shh did not induce the expression of Msx2 and Dlx5. Taken together. these data indicate that transcription factor Msx2 and Dlx5 play critical roles in the calvarial bone and suture development, and that BMP siganling is involved in the osteogenesis of calvarial bones and the maintenance of cranial sutures through regulating these two transcriotpn factors. Furthermore, different expression patterns between Msx2 and Dlx5 suggest their specific functions in the osteoblast differentiation.

• 대한예방의학회:학술대회논문집
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• 2004.10a
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• pp.40.2-41
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• 2004

• Proceedings of the Zoological Society Korea Conference
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• 2003.08a
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• pp.179.1-179
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• 2003

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.652-663
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• 1999

Craniosynostosis, the premature fusion of cranial sutures, presumably involves disturbance of the interactions between different tissues within the cranial sutures. Interestingly, point mutaions in the genes encoding for the fibroblast growth factor receptors(FGFRs), especially FGFR2, cause various types of human craniosynostosis syndromes. To elucidate the function of these genes in the early morphogenesis of mouse cranial sutures, we first analyzed by in situ hybridization the expression of FGFR2(BEK) and osteopontin, an early marker of osteogenic differentiation, in the sagittal suture of calvaria during embryonic(E15-E18) and postnatal stage(P1-P3). FGFR2(BEK) was intensely expressed in the osteogenic fronts, whose cells undergo differentiation into osteoprogenitor cells that ultimately lay down the bone matrix. Osteopontin was expressed throughout the parietal bones excluding the osteogenic fronts, the periphery of the parietal bones. To further examine the role of FGF-mediated FGFR signaling in cranial suture, we did in vitro experiments in E15.5 mouse calvarial explants. Interestingly, implantation of FGF2 soaked beads onto both the osteogenic fronts and mid-mesenchyme of sagittal suture after 36 hours organ culture resulted in the increase of the tissue thickness and cell number around FGF2 beads, moreover FGF4-soaked beads implanted onto the osteogenic fronts stimulated suture closure due to an accelerated bone growth, compared to FGF4 beads placed onto mid-mesenchyme of sagittal suture and BSA control beads. In addition FGF2 induced the ectopic expression of osteopontin and Msx1 genes. Taken together, these data indicate that FGF-mediated FGFR signaling has a important role in regulating the cranial bone growth and maintenance of cranial suture, and suggest that FGF-mediated FGFR signaling is involved in regulating the balance between the cell proliferation and differentiation through inducing the expression of osteopontin and Msx1 genes.

• Korean Journal of Cleft Lip And Palate
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• v.10 no.2
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• pp.81-88
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• 2007

Cleft lip and palate (CLP) is one of the most prevalent congenital craniofacial anomalies. It has a significantly greater incidence of dental abnormalities in number, size, shape, and eruption of the teeth. Knout-out mouse model can identify several genes which play an important role in tooth agenesis. Since disruption of these genes has been confirmed to result in tooth agenesis in humans, CLP associated with hypodontia may be the best models for isolated tooth agenesis. According to the studies of dental abnormalities in CLP, the severity of dental defect is known to be influenced by the CLP phenotype. The cumulative data obtained from mouse and human genetic studies indicated that MSX1, PAX9 and AXIN2 are considered as candidate genes in non-syndromic hypodontia, while Shh, Pitx2, Irf6, p63 and EDA pathway genes are involved in syndromic one. We expect that genetic approach of CLP can offer the basis for tooth regeneration and be a new target in hypodontia therapy.