[The hereditary fixation of the dentition. An attempt at a molecular-genetic interpretation].
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Birth Injuries↗
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Results for “ODONTOGENESIS IMPERFECTA”
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Transforming growth factor-beta1 negatively regulates crystallin expression in teeth.
Previously, we have reported that targeted overexpression of transforming growth factor (TGF) beta1 in the teeth of the transgenic mice (dTGF-beta1) results in a novel tooth phenotype phenomimicking the most prevalent tooth disorders in human. This phenotype was associated with discoloration and attrition of teeth due to defective mineralization. Here, we report a novel expression of crystallin family members in developing mouse teeth and its regulation by TGF-beta1 in these transgenic mice. AlphaB- and beta-crystallins were found to be elevated in dTGF-beta1 mouse teeth, whereas gamma-crystallin (gammaB, gammaC, and gammaF), a marker of cell differentiation, was significantly reduced. Because crystallins are believed to be stress-related proteins, their expression in teeth implicates them in a similar role because teeth are constantly subjected to physical friction and temperature fluctuations.
Amino Acid Sequence↗
Dentin matrix proteins.
Dentinogenesis consists of highly controlled events occurring a short distance from the periphery of odontoblasts: it involves formation of extracellular collagen fibrils that act as an undergirding for deposition of plate-like carbonate apatite crystals. Odontoblasts also form a set of matrix proteins that are probably secreted at the mineralization front. Although most of these proteins are similar to those of bone, and differ from soft tissue proteins, dentin contains two unique proteins. Dentin phosphoprotein (DPP) is rich in aspartic acid (D) and phosphoserine (S*) and binds large amounts of calcium. DPP contains repeating sequences of DS*S* and S*D in discrete areas of the protein. DS*S* repeats form ridges of phosphates and carboxyllates while the S*D sequences give rise to ridges with phosphates and carboxyllates on opposing sides of the peptide chain. These structures undoubtedly have functional significance since DPP is involved in promotion of mineral initiation and in control of mineral size and shape. Dentin sialoprotein (DSP), found only in dentin, is a 53 kDa glycoprotein rich in aspartic acid, serine, glutamic acid and glycine. DSP is made by odontoblasts and also by pre-ameloblasts, but not by osteoblasts or other cell types. The gene for DSP is now known to be continuous with that of DPP. Thus, DSP and DPP must be secreted as a single protein which is then proteolytically processed to form the individual components found in the dentin matrix. Significantly, the DSP/DPP gene has been localized to human chromosome 4q21 at a site implicated in dentinogenesis imperfecta type II.
Amino Acid Sequence↗
Dental enamel formation and its impact on clinical dentistry.
The nature of tooth enamel is of inherent interest to dental professionals. The current-day clinical practice of dentistry involves the prevention of enamel demineralization, the promotion of enamel remineralization, the restoration of cavitated enamel where demineralization has become irreversible, the vital bleaching of dental enamel that has become discolored, and the diagnosis and treatment of developmental enamel malformations, which can be caused by environmental or genetic factors. On a daily basis, dental health providers make diagnostic and treatment decisions that are influenced by their understanding of tooth formation. A systemic condition during tooth development, such as high fever, can produce a pattern of enamel defects in the dentition. Knowing the timing of tooth development permits estimates about the timing of the disturbance. The process of enamel maturation continues following tooth eruption, so that erupted teeth can become less susceptible to decay over time. Mutations in the genes encoding enamel proteins lead to amelogenesis imperfecta, a collection of inherited diseases having enamel malformations as the predominant phenotype. Defects in the amelogenin gene cause X-linked amelogenesis imperfecta, and genes encoding other enamel proteins are candidates for autosomal forms. Here we review our current understanding of dental enamel formation, and relate this information to clinical circumstances where this understanding may be particularly relevant.
Amelogenesis↗
Genetic variation and tooth development.
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Amelogenesis↗
Influence of microelements on the morphology of the teeth.
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Adolescent↗
Identification and characterization of a cDNA for mouse ameloblastin.
Ameloblastin was first identified as one of the most abundant novel transcripts from a random screening of a rat incisor cDNA library. In situ hybridization experiments have shown ameloblastin expression to be specific to ameloblasts, with highest levels in secretory and maturation stage ameloblasts and cells of the epithelial root sheath. Ameloblastin has been identified as a candidate gene for the local hypoplastic form of autosomal dominant amelogenesis imperfecta, by virtue of it's location within the critical disease locus. The purpose of this study was to isolate a full length mouse ameloblastin cDNA and determine its temporal expression pattern during odontogenesis. A newborn mouse molar cDNA library was screened using a rat ameloblastin cDNA probe. Positive clones were confirmed by PCR analysis with ameloblastin-specific primers, and their size determined with vector-specific primers. Phage clones were rescued to phagemid using Exassist helper phage and the nucleotide sequence determined. We report here the identification of two clones, exhibiting alternative splicing of the putative open reading frame, and use of multiple polyadenylation signals. Nucleotide sequence analysis indicated a high degree of similarity to rat ameloblastin, rat amelin 1 and 2 and porcine sheathlin. Reverse transcriptase-PCR analysis using mouse first and second mandibular molar mRNA indicated initial expression at E-14. This is one day after the initial expression of tuftelin (E-13) and one day prior to that of amelogenin (E-15).
Amino Acid Sequence↗
Molecular determinants of cranial neural crest-derived odontogenic ectomesenchyme during dentinogenesis.
Positional information on tooth morphogenesis is investigated by the identification of when and where phenotypic markers are expressed during odontogenesis. This temporal and positional information is correlated with the instructive and permissive signaling required for both dentinogenesis and amelogenesis. Of particular interest is the establishment of a map for the cranial neural crest-derived dental papilla ectomesenchyme and the odontoblast cell lineages. The expression of ectomesenchyme-derived cytotactin, dentin phosphoprotein, and epithelial-derived enamel proteins was studied in mice using embryonic, fetal, and postnatal mandibular first molar tooth organ development. This review summarizes the observations in the context of instructive epithelial-mesenchymal interactions and suggests that amelogenesis imperfecta and dentinogenesis imperfecta may in part be explained by alterations in these differentiation markers. Recombinant DNA methods should facilitate future investigations of these inherited dental disorders.
Animals↗
Targeted expression of csCSF-1 in op/op mice ameliorates tooth defects.
OBJECTIVE: The aim of this study was to characterize the tooth phenotype of CSF-1-deficient op/op mice and determine whether expression of csCSF-1 in these mice has a role in primary tooth matrix formation. DESIGN: Ameloblasts and odontoblasts, isolated from wt/wt frozen sections using laser capture microdissection, were analysed for csCSF-1, sCSF-1 and CSF-1R mRNA by RT-PCR. Mandibles, excised from 8 days op/op and wt/wt littermates, were examined for tooth morphology as well as amelogenin and DMP1 expression using in situ hybridisation. op/opCS transgenic mice, expressing csCSF-1 in teeth and bone using the osteocalcin promoter, were generated. Skeletal X-rays and histomorphometry were performed; teeth were analysed for morphology and matrix proteins. RESULTS: Normal dental cells in vivo express both CSF-1 isoforms and CSF-1R. Compared to wt/wt, op/op teeth prior to eruption showed altered dental cell morphology and dramatic reduction in DMP1 transcripts. op/opCS mice showed marked resolution of osteopetrosis, tooth eruption and teeth that resembled amelogenesis imperfecta-like phenotype. At 3 weeks, op/op teeth showed severe enamel and dentin defects and barely detectable amelogenin and DMP1. In op/opCS mice, DMP1 in odontoblasts increased to near normal and dentin morphology was restored; amelogenin also increased. Enamel integrity improved in op/opCS, although it was thinner than wt enamel. CONCLUSIONS: Results demonstrate that ameloblasts and odontoblasts are a source and potential target of CSF-1 isoforms in vivo. Expression of csCSF-1 within the tooth microenvironment is essential for normal tooth morphogenesis and may provide a mechanism for coordinating the process of tooth eruption with endogenous matrix formation.
Ameloblasts↗
Tuftelin--aspects of protein and gene structure.
The acidic enamel protein tuftelin has now been cDNA cloned, sequenced and characterized in a number of vertebrate species. Recently, the bovine tuftelin gene structure was elucidated. Cloning of the human tuftelin gene and partial sequencing of a number of exons have also been achieved. Immunologically, the protein has been shown to be conserved throughout 550 million years of vertebrate evolution. The gene has been localized to the long arm of the autosomal chromosome 1. The mapping of the human tuftelin gene to a well-defined cytogenetic region could be important in understanding the etiology of autosomally inherited amelogenesis imperfecta, the most common hereditary disease of enamel. The present paper reviews the primary structure, mRNA/cDNA structure, and gene structure of tuftelin. It describes its immunolocalization at the light microscope level and at the ultrastructural level in both the ameloblast cells and in the extracellular enamel matrix. The timing of tuftelin expression and its possible roles in enamel formation are discussed.
Ameloblasts↗
Cloning human enamelin cDNA, chromosomal localization, and analysis of expression during tooth development.
Enamelin is the largest protein in the enamel matrix of developing teeth. In the pig, enamelin is secreted as 186-kDa phosphorylated glycoprotein, which is rapidly processed by enamel proteinases into smaller cleavage products. During the secretory stage of enamel formation, enamelin is found among the crystallites in the rod and interrod enamel and comprises roughly 5% of total matrix protein. Although the function of enamelin is unknown, it is thought to participate in enamel crystal nucleation and extension, and the regulation of crystal habit. Here we report the results of enamelin in situ hybridization in a day 1 mouse developing incisor that shows that enamelin is expressed by ameloblasts, but not by odontoblasts or other cells in the dental pulp. The restricted pattern of enamelin expression makes the human enamelin gene a prime candidate in the etiology of amelogenesis imperfecta (AI), a genetic disease in which defects of enamel formation occur in the absence of non-dental symptoms. We have cloned and characterized a full-length human enamelin cDNA and determined by radiation hybrid mapping and fluorescent in situ hybridization (FISH) that the gene is located on chromosome 4q near the ameloblastin gene in a region previously linked to local hypoplastic AI in six families. These findings will facilitate the search for specific mutations in the enamelin gene in kindreds suffering from amelogenesis imperfecta.
Ameloblasts↗
MEPE/OF45, a new dentin/bone matrix protein and candidate gene for dentin diseases mapping to chromosome 4q21.
Substantial progress has been made regarding the molecular etiology of the dentin diseases dentinogenesis imperfecta types II and III, and dentin dysplasia type II. Genetic linkage studies have identified the critical loci for these diseases on human chromosome 4q21. Located within an overlapping segment of these disease loci is a dentin/bone gene cluster that includes osteopontin, bone sialoprotein, dentin matrix protein 1, dentin sialophosphoprotein, and a new gene MEPE also known as OF45, renamed osteoregulin. In this paper, we report the location of MEPE/OF45 in relationship to the other members of the dentin/bone gene cluster as well as the genomic organization of the human gene. For the first time, MEPE/OF45 expression was shown in dental tissue, in particular odontoblasts, by reverse-transcription polymerase chain reaction (RT-PCR) amplification and characterization of a partial mouse cDNA. Our data provide the first evidence that MEPE/OF45 is expressed during odontogenesis and should be considered as a candidate gene for dentin structural diseases mapping to human chromosome 4q21.
Animals↗
Amelotin--a Novel Secreted, Ameloblast-specific Protein.
We aimed to analyze the differential gene expression in various murine dental tissues, expecting to find novel factors that are involved in tooth formation. We here describe the identification of a novel ameloblast-specific gene, amelotin (AMTN), by differential display polymerase chain-reaction (DD-PCR) analysis of microdissected ameloblasts, odontoblasts, dental pulp, and alveolar bone cells of 10-day-old mouse incisors. The conceptually translated protein sequence was unique and showed significant homology only with its human orthologue. The amelotin genes from mouse and human displayed a similar exon-intron structure and were expressed from loci on chromosomes 5 and 4, respectively, which have been associated with various forms of amelogenesis imperfecta. Expression of amelotin mRNA was restricted to maturation-stage ameloblasts in developing murine molars and incisors. Amelotin protein was efficiently secreted from transfected cells in culture. Taken together, our findings suggest that amelotin is a novel factor produced by ameloblasts that plays a critical role in the formation of dental enamel.
Alveolar Process↗