High impact information on Ambn

• We found that recombinant ameloblastin adhered specifically to ameloblasts and inhibited cell proliferation [1].
• 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 [1].
• Site-directed mutagenesis of the Cbfa1-binding site (-248 base pairs) termed osteoblast-specific element 2 (OSE2) decreased ameloblastin promoter activity by greater than 50% in ameloblast-like cells [2].
• Ameloblastin is a tooth-specific extracellular matrix protein that is thought to play a role in enamel crystal formation in the developing dentition [2].
• Activity of the ameloblastin promoter in gingival and pulp fibroblasts was minimal and ranged from 8 to 30% of the activity in ameloblast-like cells [3].

Biological context of Ambn

• We have also mapped the ameloblastin gene, Ambn, to a locus on mouse chromosome 5 near other genes associated with mineralized tissues [4].
• The ameloblastin gene encodes an open reading frame of 422 amino acids corresponding to a putative protein of 45 kDa [4].
• In situ hybridization using a digoxigenin-labeled RNA probe showed that the tissue distribution of ameloblastin was limited to the ameloblast in rat incisors [4].
• A transgenic animal model resembling amelogenesis imperfecta related to ameloblastin overexpression [5].
• A newborn mouse molar cDNA library was screened using a rat ameloblastin cDNA probe [6].

Anatomical context of Ambn

• Ameloblastin was found to be expressed during the differentiation of inner enamel epithelium into ameloblasts, with intense localization in the Tomes' processes of secretory ameloblasts [4].
• We report the full-length sequencing, cell type-specific expression, and immunolocalization of a novel gene expressed in rat incisors, which we have designated ameloblastin [4].
• Ameloblastin and amelogenin expression in posnatal developing mouse molars [7].
• Amelogenin and ameloblastin show growth-factor like activity in periodontal ligament cells [8].
• Immunohistochemistry showed that DSP and ameloblastin transcripts were translated into proteins that were deposited at the apical pole of the differentiated cells (odontoblasts and ameloblasts, respectively) [9].

Other interactions of Ambn

• In contrast to amelogenin, only modest amounts of ameloblastin were detected in enamel matrix [4].
• Role of Cbfa1 in ameloblastin gene transcription [2].
• RESULTS: In the context of this yeast assay, we identified a number of secreted proteins and integral membrane proteins that interact with amelogenin, ameloblastin, and enamelin [10].
• Dentin sialophosphoprotein [designated DSPP and cleaved into dentin sialoprotein (DSP) and dentin phosphoprotein (DPP)], enamelysin and ameloblastin are each expressed in unique fashions during tooth development [9].
• In conclusion, our studies showed that the increase in enamel matrix formation by overexpression of IGFs is the result of transcriptional regulation of enamel specific proteins like amelogenin and ameloblastin but not tuftelin [11].

Analytical, diagnostic and therapeutic context of Ambn

• Positive clones were confirmed by PCR analysis with ameloblastin-specific primers, and their size determined with vector-specific primers [6].
• Cbfa1 was specifically shown to participate in the DNA-protein complexes between nuclear factors and the ameloblastin OSE2 site by supershift electrophoretic mobility shift assays [2].
• We isolated the full-length human ameloblastin (AMBN) cDNA clone using reverse transcription-polymerase chain reaction (RT-PCR) methods [12].

References