bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gene‐expression analysis of early‐ and late‐maturation‐stage rat enamel organ
Authors: Lacruz Rodrigo S. , Smith Charles E. , Chen Yi‐Bu , Hubbard Michael J. , Hacia Joseph G. , Paine Michael L. 
Published: January 2012

Lacruz RS, Smith CE, Chen Y‐B, Hubbard MJ, Hacia JG, Paine ML. Gene‐expression analysis of early‐ and late‐maturation‐stage rat enamel organ  Eur J Oral Sci 2011; 119 (Suppl. 1): 149–157. © 2011 Eur J Oral SciEnamel maturation is a dynamic process that involves high rates of mineral acquisition, associated fluctuations in extracellular pH, and resorption of extracellular enamel proteins. During maturation, ameloblasts change from having a tall, thin, and highly polarized organization, characteristic of the secretory stage, to having a low columnar and widened morphology in the maturation stage. To identify potential differences in gene expression throughout maturation, we obtained enamel organ epithelial cells derived from the early‐ and late‐maturation stages of rat incisor and analyzed the global gene‐expression profiles at each stage. Sixty‐three candidate genes were identified as having potential roles in the maturation process. Quantitative PCR was used to confirm the results of this genome‐wide analysis in a subset of genes. Transcripts enriched during late maturation (n = 38) included those associated with lysosomal activity, solute carrier transport, and calcium signaling. Also up‐regulated were transcripts involved in cellular responses to oxidative stress, proton transport, cell death, and the immune system. Transcripts down‐regulated during the late maturation stage (n = 25) included those with functions related to cell adhesion, cell signaling, and T‐cell activation. These results indicate that ameloblasts undergo widespread molecular changes during the maturation stage of amelogenesis and hence provide a basis for future functional investigations into the mechanistic basis of enamel mineralization.
Structure and function of ameloblastin as an extracellular matrix protein: adhesion, calcium binding, and CD63 interaction in human and mouse
Authors: Zhang Xu , Diekwisch Thomas G. H. , Luan Xianghong 
Published: January 2012

Zhang X, Diekwisch TGH, Luan X. Structure and function of ameloblastin as an extracellular matrix protein: adhesion, calcium binding, and CD63 interaction in human and mouse.

Eur J Oral Sci 2011; 119 (Suppl. 1): 270–279. © 2011 Eur J Oral SciThe functional significance of extracellular matrix proteins in the life of vertebrates is underscored by a high level of sequence variability in tandem with a substantial degree of conservation in terms of cell–cell and cell–matrix adhesion interactions. Many extracellular matrix proteins feature multiple adhesion domains for successful attachment to substrates, such as integrin, CD63, and heparin. Here we have used homology and ab initio modeling algorithms to compare mouse ameloblastin (mAMBN) and human ameloblastin (hABMN) isoforms and to analyze their potential for cell adhesion and interaction with other matrix molecules as well as calcium binding. Sequence comparison between mAMBN and hAMBN revealed a 26‐amino‐acid deletion in mAMBN, corresponding to a helix‐loop‐helix frameshift. The human AMBN domain (174Q–201G), homologous to the mAMBN 157E–178I helix‐loop‐helix region, formed a helix–loop motif with an extended loop, suggesting a higher degree of flexibility of hAMBN compared with mAMBN, as confirmed by molecular dynamics simulation. Heparin‐binding domains, CD63‐interaction domains, and calcium‐binding sites in both hAMBN and mAMBN support the concept of AMBN as an extracellular matrix protein. The high level of conservation between AMBN functional domains related to adhesion and differentiation was remarkable when compared with only 61% amino acid sequence homology.
An in vitro scanning microradiography study of the reduction in hydroxyapatite demineralization rate by statherin‐like peptides as a function of increasing N‐terminal length
Authors: Shah Saleha , Kosoric Jelena , Hector Mark P. , Anderson Paul 
Published: January 2012

Shah S, Kosoric J, Hector MP, Anderson P. An in vitro scanning microradiography study of the reduction in hydroxyapatite demineralization rate by statherin‐like peptides as a function of increasing N‐terminal length. Eur J Oral Sci 2011; 119 (Suppl. 1): 13–18. © 2011 Eur J Oral SciEnamel demineralization is slowed by salivary proteins that inhibit calcium hydroxyapatite (HA) demineralization. Statherin (StN43), a 43‐residue phosphorylated salivary protein with primary sequence similarities to osteopontin and caseins, binds calcium and HA. The aim of this study was to identify the minimum length of the functional domain of the statherin molecule required for cariostatic function by measuring the efficacy of peptides of progressively shorter length (i.e. containing only the N‐terminal 21 (StN21), 15 (StN15), 10 (StN10), or 5 (StN5) residues) to reduce HA demineralization rates (RDHA). Porous HA blocks were used as enamel analogues, and were exposed to 0.1 M acetic acid at pH 4 for 120 h, rinsed, and treated with StN21, StN15, StN10, or StN5 peptides (1.88 × 10−5 M) for 24 h, then demineralized for a further 120 h. The RDHA was measured, before and after peptide treatment, using scanning microradiography. Hydroxyapatite blocks treated with StN21 and StN15 demonstrated a 50–60% reduction in the RDHA. However, no reduction in the RDHA was observed following treatment with either StN10, StN5, or buffer only. The mechanism by which statherin‐like peptides reduce RDHA may be associated with their binding to HA surfaces. Comparisons with previously published binding energies of statherin to HA also suggest that statherin‐like peptides containing 15 N‐terminal residues or more, are required for binding, suggesting a link between binding and demineralization reduction.
Effect of phosphorylation on the interaction of calcium with leucine‐rich amelogenin peptide
Authors: Le Norcy Elvire , Kwak Seo‐Young , Allaire Marc , Fratzl Peter , Yamakoshi Yasuo , Simmer James P. , Margolis Henry C. 
Published: January 2012

Le Norcy E, Kwak S‐Y, Allaire M, Fratzl P, Yamakoshi Y, Simmer JP, Margolis HC. Effect of phosphorylation on the interaction of calcium with leucine‐rich amelogenin peptide.  Eur J Oral Sci 2011; 119 (Suppl. 1): 97–102. © 2011 Eur J Oral SciAmelogenin undergoes self‐assembly and plays an essential role in guiding enamel mineral formation. The leucine‐rich amelogenin peptide (LRAP) is an alternative splice product of the amelogenin gene and is composed of the N terminus (containing the only phosphate group) and the C terminus of full‐length amelogenin. This study was conducted to investigate further the role of phosphorylation in LRAP self‐assembly in the presence and absence of calcium using small angle X‐ray scattering (SAXS). Consistent with our previous dynamic light‐scattering findings for phosphorylated (+P) and non‐phosphorylated (−P) LRAP, SAXS analyses revealed radii of gyration (Rg) for LRAP(−P) (46.3–48.0 Å) that were larger than those for LRAP(+P) (25.0–27.4 Å) at pH 7.4. However, added calcium (up to 2.5 mM) induced significant increases in the Rg of LRAP(+P) (up to 46.4 Å), while it had relatively little effect on LRAP(−P) particle size. Furthermore, SAXS analyses suggested compact folded structures for LRAP(−P) in the presence and absence of calcium, whereas the conformation of LRAP(+P) changed from an unfolded structure to a more compact structure upon the addition of calcium. We conclude that the single phosphate group in LRAP(+P) induces functionally important conformational changes, suggesting that phosphorylation may also influence amelogenin conformation and protein–mineral interactions during the early stages of amelogenesis.
Developmental expression of solute carrier family 26A member 4 (SLC26A4/pendrin) during amelogenesis in developing rodent teeth
Authors: Bronckers Antonius L. J. J. , Guo Jing , Zandieh‐Doulabi Behrouz , Bervoets Theodore J. , Lyaruu Donacian M. , Li Xiangming , Wangemann Philine , DenBesten Pamela 
Published: January 2012

Bronckers ALJJ, Guo J, Zandieh‐Doulabi B, Bervoets TJ, Lyaruu DM, Li X, Wangemann P, DenBesten P. Developmental expression of solute carrier family 26A member 4 (SLC26A4/pendrin) during amelogenesis in developing rodent teeth.

Eur J Oral Sci 2011; 119 (Suppl. 1): 185–192. © 2011 Eur J Oral SciAmeloblasts need to regulate pH during the formation of enamel crystals, a process that generates protons. Solute carrier family 26A member 4 (SLC26A4, or pendrin) is an anion exchanger for chloride, bicarbonate, iodine, and formate. It is expressed in apical membranes of ion‐transporting epithelia in kidney, inner ear, and thyroid where it regulates luminal pH and fluid transport. We hypothesized that maturation ameloblasts express SLC26A4 to neutralize acidification of enamel fluid in forming enamel. In rodents, secretory and maturation ameloblasts were immunopositive for SLC26A4. Staining was particularly strong in apical membranes of maturation ameloblasts facing forming enamel. RT‐PCR confirmed the presence of mRNA transcripts for Slc26a4 in enamel organs. SLC26A4 immunostaining was also found in mineralizing connective tissues, including odontoblasts, osteoblasts, osteocytes, osteoclasts, bone lining cells, cellular cementoblasts, and cementocytes. However, Slc26a4‐null mutant mice had no overt dental phenotype. The presence of SLC26A4 in apical plasma membranes of maturation ameloblasts is consistent with a potential function as a pH regulator. SLC26A4 does not appear to be critical for ameloblast function and is probably compensated by other pH regulators.
Fluoride incorporation into apatite crystals delays amelogenin hydrolysis
Authors: DenBesten Pamela K. , Zhu Li , Li Wu , Tanimoto Kotaro , Liu Haichuan , Witkowska Halina E. 
Published: January 2012

DenBesten PK, Zhu L, Li W, Tanimoto K, Liu H, Witkowska HE. Fluoride incorporation into apatite crystals delays amelogenin hydrolysis.

Eur J Oral Sci 2011; 119 (Suppl. 1): 3–7. © 2011 Eur J Oral SciEnamel fluorosis has been related to an increase in the amount of amelogenin in fluorosed enamel compared with normal enamel in the maturation stage. In this study we tested the hypothesis that fluoride incorporated into carbonated apatite alters amelogenin hydrolysis. Recombinant human amelogenin (rh174) was allowed to bind to 0.15 mg of carbonated hydroxyapatite (CAP) or to fluoride‐containing carbonated hydroxyapatite (F‐CAP) synthesized to contain 100, 1,000, or 4,000 ppm F−. After 3 h of digestion with recombinant human matrix metalloproteinase 20 (MMP20) or kallikrein‐related peptidase 4 (KLK4), bound protein was characterized by reverse‐phase high‐performance liquid chromatography (HPLC). Proteolytic fragments of amelogenin formed after 24h of digestion with MMP20 of KLK 4 were identified by liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). The hydrolysis, by both MMP20 and KLK4, of amelogenin bound to F100‐CAP was significantly reduced in a dose‐dependent manner compared with the hydrolysis of amelogenin bound to CAP. After 24 h of hydrolysis, a similar number of MMP20 cleavage sites was found for amelogenin bound to CAP and amelogenin bound to F100‐CAP; however, 24 fewer KLK4 cleavage sites were identified for amelogenin bound to F100‐CAP than for amelogenin bound to CAP. These results suggest that the reduced hydrolysis of amelogenins in fluorosed enamel may be partially caused by the increased fluoride content in fluoride‐containing apatite, contributing to the hypomineralized enamel matrix phenotype observed in fluorosed enamel.
Distribution of enamel crystallite orientation through an entire tooth crown studied using synchrotron X‐ray diffraction
Authors: Simmons Lisa M. , Al‐Jawad Maisoon , Kilcoyne Susan H. , Wood David J. 
Published: January 2012

Simmons LM, Al‐Jawad M, Kilcoyne SH, Wood DJ. Distribution of enamel crystallite orientation through an entire tooth crown studied using synchrotron X‐ray diffraction.

Eur J Oral Sci 2011; 119 (Suppl. 1): 19–24. © 2011 Eur J Oral SciThe biomineralization of human dental enamel has resulted in a highly anisotropic and heterogeneous distribution of hydroxyapatite crystallites, which in combination with its high mineral content has resulted in one of the most durable and hardest tissues in the human body. In this study, we used position‐sensitive synchrotron X‐ray diffraction to quantify the spatial variation in the direction and magnitude of the preferred orientation of enamel crystallites across a whole tooth crown. Two‐dimensional synchrotron X‐ray diffraction images were collected with 300 μm spatial resolution over a series of six sequential tooth sections obtained from a single maxillary first premolar and were analyzed using Rietveld refinement. Both the magnitude and the direction of the crystallite orientation were found to have a high spatial heterogeneity. Areas of high crystallite alignment were directed perpendicular to the biting surfaces, which is thought to meet the functional requirements of mastication. The results may assist in our understanding of the structure–function relationship and of the evolutionary development of enamel.
Ameloblastin upstream region contains structural elements regulating transcriptional activity in a stromal cell line derived from bone marrow
Authors: Tamburstuen Margareth V. , Snead Malcolm L. , Reseland Janne E. , Paine Michael L. , Lyngstadaas Staale P. 
Published: January 2012

Tamburstuen MV, Snead ML, Reseland JE, Paine ML, Lyngstadaas SP. Ameloblastin upstream region contains structural elements regulating transcriptional activity in a stromal cell line derived from bone marrow. Eur J Oral Sci 2011; 119 (Suppl. 1): 286–292. © 2011 Eur J Oral SciAmeloblastin (AMBN) was originally described as a tooth‐specific extracellular matrix protein, but current data have shown that AMBN is present in many different tissues of mesenchymal origin. The identification of regulatory elements in the promoter region of theAmbngene would assist in identifying potential mesenchymal‐specific transcriptional factors. In this study we subcloned a 3,788‐bp region upstream (and a 54‐bp region downstream) of the mouseAmbntranscriptional start site into aLacZreporter construct and called this construct 3788‐Ambn‐lacZ.In silicoanalysis of the 3,788‐bpAmbnpromoter region identified 50 potential cis‐regulatory elements, 29 of which are known to be functional in cell populations of mesenchymal origin. The reporter construct was activated in transfected bone marrow cells, and the promoter activity was induced in cell cultures following addition of recombinant AMBN, interferon‐γ, serotonin, or dexamethasone. We discuss the relative significance of the potential cis‐acting gene‐regulatory elements ofAmbnin relation to bone morphogenesis. Knowledge ofAmbngene‐regulatory elements will be of importance when developing strategies for bone repair and replacement in a clinical surgical setting.
Regulation of calcium phosphate formation by amelogenins under physiological conditions
Authors: Kwak Seo‐Young , Green Samantha , Wiedemann‐Bidlack Felicitas B. , Beniash Elia , Yamakoshi Yasuo , Simmer James P. , Margolis Henry C. 
Published: January 2012

Kwak S‐Y, Green S, Wiedemann‐Bidlack FB, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Regulation of calcium phosphate formation by amelogenins under physiological conditions.  Eur J Oral Sci 2011; 119 (Supp. 1): 103–111. © 2011 Eur J Oral SciAmelogenin is essential for proper enamel formation. The present in vitro study extends our previous work at low (10 mM) ionic strength (IS) by examining the effect of amelogenin on mineralization under higher (162 mM) IS conditions found in developing enamel. Full‐length phosphorylated (P173) and non‐phosphorylated (rP172) amelogenins were examined, along with P148 and rP147 that lack the hydrophilic C‐terminus. Calcium phosphate formation was assessed by pH change, while the minerals formed were characterized using transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. Amelogenin self‐assembly was also studied using dynamic light scattering and TEM. The results indicate that IS does not influence the effects of rP147, rP172, and P173 on mineralization. However, in contrast to the findings for low IS, where both P173 and P148 stabilize initially formed amorphous calcium phosphate (ACP) nanoparticles for >1 d, elongated hydroxyapatite crystals were observed after 24 h using P148 at high IS, unlike that seen with P173. Differences in self‐assembly help explain these findings, which suggest that P173 and P148 may play different roles in regulating enamel mineral formation. The present data support the notion that proteolytic processing of P173 is required in vivo to induce the transformation of initial ACP phases to apatitic enamel crystals.
Human osteoblastic cells discriminate between 20‐kDa amelogenin isoforms
Authors: Riksen Elisabeth A. , Petzold Christiane , Brookes Steven , Lyngstadaas Ståle P. , Reseland Janne E. 
Published: January 2012

Riksen EA, Petzold C, Brookes S, Lyngstadaas SP, Reseland JE. Human osteoblastic cells discriminate between 20‐kDa amelogenin isoforms.  Eur J Oral Sci 2011; 119 (Suppl. 1): 357–365. © 2011 Eur J Oral SciEnamel matrix derivative (EMD) is used to stimulate healing of alveolar bone after destructive marginal periodontitis; however, the roles of the different EMD constituents are unclear. The aim here was to compare the effect of two EMD fractions (A1 and A2) on primary human osteoblasts cultured in the presence of 50 μg ml−1 of A1, A2, or EMD. SDS‐PAGE showed that A1 and A2 were comprised of amelogenins migrating at around 20 kDa. Fourier transform infrared (FTIR) analysis revealed that A1 and A2 had different secondary structures, and matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) identified different peptide mass values. Osteoblasts responded differently to A1 and A2. Whereas A1 enhanced the proliferation [measured by the incorporation of 5‐bromo‐2′‐deoxyuridine (BrdU)] of osteoblasts, the expression of runt‐related transcription factor‐2 (RUNX2) mRNA, and the secretion of interleukin 6 (IL‐6) into the cell culture medium, exposure to A2 resulted in increased alkaline phosphatase (ALP) activity, increased expression of CD44 mRNA, and increased secretion of osteoprotegrin (OPG) and receptor activator of nuclear factor‐kappaB ligand (RANKL). The level of osteocalcin in the cell culture medium was increased after all treatments, while A2 stimulated the expression of dentin matrix protein 1 (DMP1) mRNA. The results suggest that both A1 and A2 participate in the observed effect of EMD, but have different effects on the expression of osteoblast mRNA and the secretion of osteoblast protein, and thus might facilitate the differentiation of a different phenotype.
Biophysical characterization of recombinant human ameloblastin
Authors: Wald Tomáš , Bednárová Lucie , Osička Radim , Pachl Petr , Šulc Miroslav , Lyngstadaas Stale Petter , Slaby Ivan , Vondrášek Jiří 
Published: January 2012

Wald T, Bednárová L, Osička R, Pachl P, Šulc M, Lyngstadaas SP, Slaby I, Vondrášek J. Biophysical characterization of recombinant human ameloblastin.

Eur J Oral Sci 2011; 119 (Suppl. 1): 261–269. © 2011 Eur J Oral SciAmeloblastin (AMBN) is a protein expressed mainly during dental hard tissue development. Biochemically, it is classified as an intrinsically disordered protein (IDP). Its biological role remains largely unknown; however, the question of AMBN function will undoubtedly be connected to its structural properties and its potential for protein–protein and protein–cell interactions. A basic biophysical characterization of human recombinant ameloblastin (hrAMBN) and its N‐ and C‐terminal domains by means of circular dichroism spectroscopy and dynamic light scattering showed that under physiological conditions ameloblastin is an IDP with a prevalent polyproline‐II (PPII) conformation. Both the N‐ and C‐terminal polypeptides, when expressed independently, showed different structural preferences upon heating as well as different behaviour in the presence of trifluoroethanol and CaCl2 salt. The N‐terminal peptide showed a more ordered structure with a strong tendency to adopt a helical conformation upon the addition of trifluorethanol, whereas the C‐terminal domain seemed to be primarily responsible for the structural disorder of the entire AMBN molecule.
Molecular and circadian controls of ameloblasts
Authors: Athanassiou‐Papaefthymiou Maria , Kim Doohak , Harbron Lindsay , Papagerakis Silvana , Schnell Santiago , Harada Hidemitsu , Papagerakis Petros 
Published: January 2012

Athanassiou‐Papaefthymiou M, Kim D, Harbron L, Papagerakis S, Schnell S, Harada H, Papagerakis P. Molecular and circadian controls of ameloblasts.

Eur J Oral Sci 2011; 119 (Suppl. 1): 35–40. © 2011 Eur J Oral SciStage‐specific expression of ameloblast‐specific genes is controlled by differential expression of transcription factors. In addition, ameloblasts follow daily rhythms in their main activities (i.e. enamel protein secretion and enamel mineralization). This time‐related control is orchestrated by oscillations of clock proteins involved in the regulation of circadian rhythms. Our aim was to identify the potential links between daily rhythms and developmental controls of ameloblast differentiation. The effects of the transcription factors distal‐less homeobox 3 (Dlx3) and runt‐related transcription factor 2 (Runx2), and the clock gene nuclear receptor subfamily 1, group D, member 1 (Nr1d1), on secretory and maturation ameloblasts [using stage‐specific markers amelogenin (Amelx), enamelin (Enam), and kallikrein‐related peptidase 4 (Klk4)] were evaluated in the HAT‐7 ameloblast cell line. Amelx and Enam steady‐state mRNA expression levels were down‐regulated in Runx2 over‐expressing cells and up‐regulated in Dlx3 over‐expressing cells. In contrast, Klk4 mRNA was up‐regulated by both Dlx3 and Runx2. Furthermore, a temporal and spatial relationship between clock genes and ameloblast differentiation markers was detected. Of interest, clock genes not only affected rhythmic expression of ameloblast‐specific genes but also influenced the expression of Runx2. Multiscale mathematical modeling is being explored to further understand the temporal and developmental controls of ameloblast differentiation. Our study provides novel insights into the regulatory mechanisms sustaining ameloblast differentiation.