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Ameloblastin is a cell adhesion molecule required for maintaining the differentiation state of ameloblasts.

Fukumoto S, Kiba T, Hall B, Iehara N, Nakamura T, Longenecker G, Krebsbach PH, Nanci A, Kulkarni AB, Yamada Y - J. Cell Biol. (2004)

Bottom Line: Tooth morphogenesis results from reciprocal interactions between oral epithelium and ectomesenchyme culminating in the formation of mineralized tissues, enamel, and dentin.We found that recombinant ameloblastin adhered specifically to ameloblasts and inhibited cell proliferation.Thus, ameloblastin is a cell adhesion molecule essential for amelogenesis, and it plays a role in maintaining the differentiation state of secretory stage ameloblasts by binding to ameloblasts and inhibiting proliferation.

View Article: PubMed Central - PubMed

Affiliation: Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Tooth morphogenesis results from reciprocal interactions between oral epithelium and ectomesenchyme culminating in the formation of mineralized tissues, enamel, and dentin. During this process, epithelial cells differentiate into enamel-secreting ameloblasts. Ameloblastin, an enamel matrix protein, is expressed by differentiating ameloblasts. Here, we report the creation of ameloblastin- mice, which developed severe enamel hypoplasia. In mutant tooth, the dental epithelium differentiated into enamel-secreting ameloblasts, but the cells were detached from the matrix and subsequently lost cell polarity, resumed proliferation, and formed multicell layers. Expression of Msx2, p27, and p75 were deregulated in mutant ameloblasts, the phenotypes of which were reversed to undifferentiated epithelium. We found that recombinant ameloblastin adhered specifically to ameloblasts and inhibited cell proliferation. The mutant mice developed an odontogenic tumor of dental epithelium origin. Thus, ameloblastin is a cell adhesion molecule essential for amelogenesis, and it plays a role in maintaining the differentiation state of secretory stage ameloblasts by binding to ameloblasts and inhibiting proliferation.

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Ameloblastin binds dental epithelium and inhibits proliferation of Ambn−/− ameloblasts. (A) Adhesion of dental epithelial cells isolated from P3 molars to dishes coated with various amounts of recombinant ameloblastin. pEF6 is a control protein containing only the His-tagged portion purified from mock-transfected cells (pEF6, square). (B) Cell type–specific adhesion to recombinant ameloblastin. Various types of cells were plated on dishes coated with ameloblastin (10 μg/plate), and bound cells were counted. DE, dental epithelial cells. (C) Inhibition of ameloblast proliferation by maeloblastin. Dental epithelial cells from normal and mutant P7 molars were incubated on plates without (left) or with recombinant ameloblastin (right; 10 μg/plate). Plating cell numbers at day 0 are set as 100%. Proliferation of cells from P7 mutant mice are significantly inhibited by ameloblastin. Data are expressed as mean of triplicate results.
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fig7: Ameloblastin binds dental epithelium and inhibits proliferation of Ambn−/− ameloblasts. (A) Adhesion of dental epithelial cells isolated from P3 molars to dishes coated with various amounts of recombinant ameloblastin. pEF6 is a control protein containing only the His-tagged portion purified from mock-transfected cells (pEF6, square). (B) Cell type–specific adhesion to recombinant ameloblastin. Various types of cells were plated on dishes coated with ameloblastin (10 μg/plate), and bound cells were counted. DE, dental epithelial cells. (C) Inhibition of ameloblast proliferation by maeloblastin. Dental epithelial cells from normal and mutant P7 molars were incubated on plates without (left) or with recombinant ameloblastin (right; 10 μg/plate). Plating cell numbers at day 0 are set as 100%. Proliferation of cells from P7 mutant mice are significantly inhibited by ameloblastin. Data are expressed as mean of triplicate results.

Mentions: We examined the binding of ameloblastin to cells. Recombinant His-tagged ameloblastin was produced in COS7 cells, purified by affinity chromatography and used for cell adhesion assays (Fig. 7). Dental epithelial cells from P3 molars adhered dishes coated with ameloblastin in a dose-dependent manner, whereas a control His-tagged protein showed no cell adhesion (Fig. 7 A). Cell binding activity of ameloblastin appears to be specific to dental epithelium because ameloblastin did not support cell adhesion to other cells including kidney epithelial cell line MDCK (Fig. 7 B). We next examined substrate-specific adhesion of ameloblasts from wild-type tooth (Table I). Because primary dental epithelial cells isolated from P7 molars contain mixed cell populations, we distinguished between preameloblast and ameloblast cell types that had adhered to substrates by immunostaining of integrin α6 and amelogenin. We found that ameloblasts (amelogenin positive and integrin α6 negative) adhered to ameloblastin, but not fibronectin and laminin 10/11. In contrast, preameloblasts (integrin α6 positive and amelogenin negative) adhered to fibronectin and laminin 10/11, but not ameloblastin. Intermediate stage cells (positive for both amelogenin and integrin α6) adhered to all three substrates. These results suggest that ameloblasts but not preameloblasts preferentially adhered to ameloblastin.


Ameloblastin is a cell adhesion molecule required for maintaining the differentiation state of ameloblasts.

Fukumoto S, Kiba T, Hall B, Iehara N, Nakamura T, Longenecker G, Krebsbach PH, Nanci A, Kulkarni AB, Yamada Y - J. Cell Biol. (2004)

Ameloblastin binds dental epithelium and inhibits proliferation of Ambn−/− ameloblasts. (A) Adhesion of dental epithelial cells isolated from P3 molars to dishes coated with various amounts of recombinant ameloblastin. pEF6 is a control protein containing only the His-tagged portion purified from mock-transfected cells (pEF6, square). (B) Cell type–specific adhesion to recombinant ameloblastin. Various types of cells were plated on dishes coated with ameloblastin (10 μg/plate), and bound cells were counted. DE, dental epithelial cells. (C) Inhibition of ameloblast proliferation by maeloblastin. Dental epithelial cells from normal and mutant P7 molars were incubated on plates without (left) or with recombinant ameloblastin (right; 10 μg/plate). Plating cell numbers at day 0 are set as 100%. Proliferation of cells from P7 mutant mice are significantly inhibited by ameloblastin. Data are expressed as mean of triplicate results.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172447&req=5

fig7: Ameloblastin binds dental epithelium and inhibits proliferation of Ambn−/− ameloblasts. (A) Adhesion of dental epithelial cells isolated from P3 molars to dishes coated with various amounts of recombinant ameloblastin. pEF6 is a control protein containing only the His-tagged portion purified from mock-transfected cells (pEF6, square). (B) Cell type–specific adhesion to recombinant ameloblastin. Various types of cells were plated on dishes coated with ameloblastin (10 μg/plate), and bound cells were counted. DE, dental epithelial cells. (C) Inhibition of ameloblast proliferation by maeloblastin. Dental epithelial cells from normal and mutant P7 molars were incubated on plates without (left) or with recombinant ameloblastin (right; 10 μg/plate). Plating cell numbers at day 0 are set as 100%. Proliferation of cells from P7 mutant mice are significantly inhibited by ameloblastin. Data are expressed as mean of triplicate results.
Mentions: We examined the binding of ameloblastin to cells. Recombinant His-tagged ameloblastin was produced in COS7 cells, purified by affinity chromatography and used for cell adhesion assays (Fig. 7). Dental epithelial cells from P3 molars adhered dishes coated with ameloblastin in a dose-dependent manner, whereas a control His-tagged protein showed no cell adhesion (Fig. 7 A). Cell binding activity of ameloblastin appears to be specific to dental epithelium because ameloblastin did not support cell adhesion to other cells including kidney epithelial cell line MDCK (Fig. 7 B). We next examined substrate-specific adhesion of ameloblasts from wild-type tooth (Table I). Because primary dental epithelial cells isolated from P7 molars contain mixed cell populations, we distinguished between preameloblast and ameloblast cell types that had adhered to substrates by immunostaining of integrin α6 and amelogenin. We found that ameloblasts (amelogenin positive and integrin α6 negative) adhered to ameloblastin, but not fibronectin and laminin 10/11. In contrast, preameloblasts (integrin α6 positive and amelogenin negative) adhered to fibronectin and laminin 10/11, but not ameloblastin. Intermediate stage cells (positive for both amelogenin and integrin α6) adhered to all three substrates. These results suggest that ameloblasts but not preameloblasts preferentially adhered to ameloblastin.

Bottom Line: Tooth morphogenesis results from reciprocal interactions between oral epithelium and ectomesenchyme culminating in the formation of mineralized tissues, enamel, and dentin.We found that recombinant ameloblastin adhered specifically to ameloblasts and inhibited cell proliferation.Thus, ameloblastin is a cell adhesion molecule essential for amelogenesis, and it plays a role in maintaining the differentiation state of secretory stage ameloblasts by binding to ameloblasts and inhibiting proliferation.

View Article: PubMed Central - PubMed

Affiliation: Craniofacial Developmental Biology and Regeneration Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA.

ABSTRACT
Tooth morphogenesis results from reciprocal interactions between oral epithelium and ectomesenchyme culminating in the formation of mineralized tissues, enamel, and dentin. During this process, epithelial cells differentiate into enamel-secreting ameloblasts. Ameloblastin, an enamel matrix protein, is expressed by differentiating ameloblasts. Here, we report the creation of ameloblastin- mice, which developed severe enamel hypoplasia. In mutant tooth, the dental epithelium differentiated into enamel-secreting ameloblasts, but the cells were detached from the matrix and subsequently lost cell polarity, resumed proliferation, and formed multicell layers. Expression of Msx2, p27, and p75 were deregulated in mutant ameloblasts, the phenotypes of which were reversed to undifferentiated epithelium. We found that recombinant ameloblastin adhered specifically to ameloblasts and inhibited cell proliferation. The mutant mice developed an odontogenic tumor of dental epithelium origin. Thus, ameloblastin is a cell adhesion molecule essential for amelogenesis, and it plays a role in maintaining the differentiation state of secretory stage ameloblasts by binding to ameloblasts and inhibiting proliferation.

Show MeSH
Related in: MedlinePlus