PubMed Health⌕ Search

Biomedical subjects

Juan Dong

Publications and source records attributed to Juan Dong.

13 recordsLinked to original sources
PubMed2006

Molecular basis of human dentin diseases.

In recent years, substantial progress has been made regarding the molecular etiology of human structural tooth diseases that alter dentin matrix formation. These diseases have been classified into two major groups with subtypes: dentin dysplasia (DD) types I and II and dentinogenesis imperfecta (DGI) types I-III. Genetic linkage studies have identified the critical loci for DD-II, DGI-II, and DGI-II to human chromosome 4q21. Located within the common disease loci for these diseases is cluster of dentin/bone genes that includes osteopontin (OPN), bone sialoprotein (BSP), matrix extracellular phosphoglycoprotein (MEPE), dentin matrix protein 1 (DMP1), and dentin sialophosphoprotein (DSPP). To date, only mutations within dentin sialophosphoprotein have been associated with the pathogenesis of dentin diseases including DGI types-II and -III and DD-II. In this article, we overview the recent literature related to these dentin genetic diseases, their clinical features, and molecular pathogenesis.

Chromosome Mapping↗
PubMed2006

Exogenous free ubiquitin enhances lily pollen tube adhesion to an in vitro stylar matrix and may facilitate endocytosis of SCA.

Pollen tube adhesion and guidance on extracellular matrices within the pistil are essential processes that convey the pollen tube cell and the sperm cells to the ovule. In this study, we purified an additional molecule from the pistil that enhances pollen tube adhesion when combined with the SCA (stigma/stylar cysteine-rich adhesin)/pectin matrix in our in vitro assay. The enhancer of adhesion was identified as free ubiquitin (Ub). This was confirmed by use of bovine Ub as a substitute for lily (Lilium longiflorum Thunb.) stigma Ub. To study the interaction of SCA and Ub with the lily pollen tube, we labeled both proteins with biotin. We observed uptake of biotin-labeled SCA and Ub into the pollen tube cells in vitro using confocal microscopy. For SCA, a strong signal occurred first at the tip of the pollen tube, suggestive of an endocytosis event, and then progressively throughout the tube cytoplasm. SCA was also localized inside the in vivo pollen tube using immunogold electron microscopy and found to be present in endosomes, multivesicular bodies, and vacuoles, all known to be endocytic compartments. It was also confirmed that SCA is endocytosed in the in vitro adhesion assay. Internalization of SCA was increased in pollen tubes treated with exogenous Ub compared to those without Ub, suggesting that Ub may facilitate SCA endocytosis. These results show that Ub can act as an enhancer of pollen tube adhesion in vitro and that it is taken up into the pollen tube as is SCA. The Ub machinery may play a role in pollen tube adhesion and guidance in lily.

Amino Acid Sequence↗
PubMed2006

Generation and characterization of a transgenic mouse model for pancreatic cancer.

AIM: To generate a SV40Tag transgenic tumor animal model and to study the mechanism underlying tumorigenesis. METHODS: A mammary gland expression vector containing SV40Tag DNA was generated. Transgene fragments were microinjeted into fertilized eggs of FVB mice. The genetically manipulated embryos were transferred into the oviducts of pseudo-pregnant female mice. PCR and Northern blot analysis were used for genotype analysis of F1 and F2 mice. Transgene expression was detected by RT-PCR and immunohistochemistry. RESULTS: SV40Tag gene was detected in two lines of transgenic mice. One of them delivered the transgene to F1 and a tumor was found in the pancreas of these mice. RT-PCR and immunohistochemistry showed that SV40Tag gene was expressed in the tumor. Pathological characterization of the transgenic mice demonstrated that the tumor belonged to pancreatic cystic neoplasm. CONCLUSION: SV40Tag transgenic mouse model can be successfully established. The transgenic mice develop a pancreatic tumor, which can be used for investigation of the molecular mechanism of tumorigenesis in vivo.

Animals↗
PubMed2006

Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection.

A simple method for separation of different anionic and zwitterionic phospholipid classes by capillary zone electrophoresis (CZE), using indirect UV detection with adenosine monophosphate (AMP) as background electrolyte and the UV-absorbing additive, was successfully developed in this study. The separation conditions including apparent pH (pH*) of running buffer, concentration of AMP, organic solvent, applied voltage and capillary temperature were systematically optimized. The application of this method to human blood sample was also briefly examined.

Adenosine Monophosphate↗
PubMed2005

Plantacyanin plays a role in reproduction in Arabidopsis.

Plantacyanins belong to the phytocyanin family of blue copper proteins. In the Arabidopsis (Arabidopsis thaliana) genome, only one gene encodes plantacyanin. The T-DNA-tagged mutant is a knockdown mutant that shows no visible phenotype. We used both promoter-beta-glucuronidase transgenic plants and immunolocalization to show that Arabidopsis plantacyanin is expressed most highly in the inflorescence and, specifically, in the transmitting tract of the pistil. Protein levels show a steep gradient in expression from the stigma into the style and ovary. Overexpression plants were generated using cauliflower mosaic virus 35S, and protein levels in the pistil were examined as well as the pollination process. Seed set in these plants is highly reduced mainly due to a lack of anther dehiscence, which is caused by degeneration of the endothecium. Callose deposits occur on the pollen walls in plants that overexpress plantacyanin, and a small percentage of these pollen grains germinate in the closed anthers. When wild-type pollen was used on the overexpression stigma, seed set was still decreased compared to the control pollinations. We detected an increase in plantacyanin levels in the overexpression pistil, including the transmitting tract. Guidance of the wild-type pollen tube on the overexpression stigma is disrupted as evidenced by the growth behavior of pollen tubes after they penetrate the papillar cell. Normally, pollen tubes travel down the papilla cell and into the style. Wild-type pollen tubes on the overexpression stigma made numerous turns around the papilla cell before growing toward the style. In some rare cases, pollen tubes circled up the papilla cell away from the style and were arrested there. We propose that when plantacyanin levels in the stigma are increased, pollen tube guidance into the style is disrupted.

Arabidopsis↗
PubMed2005

DLX3 mutation associated with autosomal dominant amelogenesis imperfecta with taurodontism.

Amelogenesis imperfecta hypoplastic-hypomaturation with taurodontism (AIHHT) is an autosomal dominant (AD) trait associated with enamel defects and enlarged pulp chambers. In this study, we mapped an AIHHT family to human chromosome 17 q21-q22 (lod score 3.3) and identify a two basepair deletion (CT) at nucleotide 560 in DLX3 associated with the disease. This mutation causes a frameshift altering the last two amino acids of the DNA-binding homeodomain introducing a premature stop codon truncating the protein by 88 amino acids. This is the first report of a mutation within the homeodomain of DLX3. Previous studies have shown a DLX3 mutation outside the homeodomain associated with tricho-dento-osseous syndrome (TDO) suggesting TDO and some forms of AIHHT are allelic.

Abnormalities, Multiple↗
PubMed2005

Dentin phosphoprotein compound mutation in dentin sialophosphoprotein causes dentinogenesis imperfecta type III.

A rare compound mutation involving a 36 bp deletion and 18 bp insertion within exon 5 of the dentin sialophosphoprotein (DSPP) gene has been identified in a family with dentinogenesis imperfecta type III (DGI-III). The DSPP gene encodes two major tooth matrix proteins dentin sialoprotein (DSP) and dentin phosphoprotein (DPP). DSPP mutations associated with DGI-III results in an in frame truncation of the serine aspartic acid triplet repeat found in DPP near the highly conserved carboxyl terminal region shortening the protein by six amino acids. Clinically this family presents with discolored amber opalescent teeth and severe attrition of the tooth structure. This study is the first report of a mutation within DPP associated with a genetic dentin disease. Our study indicates that DGI-III is allelic with some forms of DGI-II with and without progressive hearing loss and dentin dysplasia type II that have been shown to be caused by mutations within the DSP coding or signal peptide regions.

Amino Acid Sequence↗
PubMed2005

[Expression of lung resistance protein and multidrug resistance-associated protein in naive childhood acute leukemia and their clinical significance].

BACKGROUND & OBJECTIVE: Previous studies revealed that lung resistance protein (LRP) and multidrug resistance-associated protein (MRP) relate to drug resistance of childhood leukemia, which is not caused by only one mechanism. This study was to evaluate the expression of LRP and MRP genes in childhood leukemia and their correlation. METHODS: The expression of LRP and MRP in 38 children with acute leukemia and 6 healthy children were measured with reverse transcription-polymerase chain reaction (RT-PCR); their clinical significance was analyzed according to complete remission (CR) rate of the patients after chemotherapy. RESULTS: CR rate of the 38 patients was 68.4%. LRP was expressed in 11 of the 38 patients, and didn't express in healthy controls; CR rate was significantly lower in LRP-positive patients than in LRP-negative patients (27.3% vs. 85.2%, P < 0.05). MRP was overexpressed in 21 of the 38 patients; CR rate was significantly lower in MRP-positive patients than in MRP-negative patients (47.6% vs. 94.1%, P < 0.05). The positive rate of LRP was significantly lower in acute lymphoblastic leukemia (ALL) than in acute nonlymphocytic leukemia (ANLL) [18.5% (5/27) vs. 45.5% (6/11), P < 0.05]; however, the positive rate of MRP was 59.3% (16/27) in ALL, and 45.5% (5/11) in ANLL (P > 0.05). The positive rate of MRP was 28.6% in LRP-positive patients, and 29.4% in LRP-negative patients; there was no correlation between LRP and MRP. CONCLUSION: Childhood acute leukemia patients with overexpression of LRP and MRP suffer severe disease and achieve low remission rateû lower remission rate of childhood ANLL patients may relate to LRP expression.

Adolescent↗
PubMed2004

Regulation of the Cell Type-specific dentin sialophosphoprotein gene expression in mouse odontoblasts by a novel transcription repressor and an activator CCAAT-binding factor.

Dentin sialophosphoprotein (DSPP) is an extracellular matrix protein that is cleaved into dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) with a highly restricted expression pattern in tooth and bone. Mutations of the DSPP gene are associated with dentin genetic diseases. Regulation of tissue-specific DSPP expression has not been described. To define the molecular basis of this cell-specific expression, we characterized the promoter responsible for the cell-specific expression of the DSPP gene in odontoblasts. Within this region, DNase I footprinting and electrophoretic mobility shift assays delineated one element that contains an inverted CCAAT-binding factor site and a protein-DNA binding site using nuclear extracts from odontoblasts. A series of competitive electrophoretic mobility shift assay analyses showed that the protein-DNA binding core sequence, ACCCCCA, is a novel site sufficient for protein binding. These two protein-DNA binding sequences are conserved at the same proximal position in the mouse, rat, and human DSPP gene promoters and are ubiquitously present in the promoters of other tooth/bone genes. Mutations of the CCAAT-binding factor binding site resulted in a 5-fold decrease in promoter activity, whereas abolishment of the novel protein-DNA binding site increased promoter activity by about 4.6-fold. In contrast to DSPP, expression levels of the novel protein were significantly reduced during odontoblastic differentiation and dentin mineralization. The novel protein was shown to have a molecular mass of 72 kDa. This study shows that expression of the cell type-specific DSPP gene is mediated by the combination of inhibitory and activating mechanisms.

Animals↗
PubMed2004

Binding of two nuclear factors to a novel silencer element in human dentin matrix protein 1 (DMP1) promoter regulates the cell type-specific DMP1 gene expression.

DMP1 is an acidic phosphorylated protein with the spatial and temporal expression that is largely restricted to bone and tooth tissues. The biological function of DMP1 is associated with biomineralization of bone, cartilage and tooth development. To study the cell-specific expression of DMP1, a 2,512 bp upstream segment of the human gene was isolated and characterized. A series of progressive deletions of the human DMP1 5' flanking sequence were ligated to the luciferase reporter gene, and their promoter activities examined in transfected human osteoblast-like (MG-63) and dental pulp (HDP-D) cells that express DMP1 and hepatic (HepG2) and uterine (HeLa) cells lacking DMP1 expression. A critical cis-regulatory element located between nt -150 and -63 was found to act as a specific silencer responsible for the negative regulation of DMP1 in HepG2 and HeLa cells. The transcriptional activity of this element in MG-63 and HDP-D cells had a 5-7-fold increase than that observed in HepG2 and HeLa cells. Electrophoretic mobility shift assays (EMSAs) showed that a 6-bp DNA sequence in this element was bound by two nuclear factors that are expressed at high levels in HepG2 and HeLa versus MG-63 and HDP-D cells. Competitive assays by EMSAs suggest that the 6-bp core DNA sequence, AG(T/C)C(A/G)C, is a novel DNA-protein binding site and conserved with high identity in reported DMP1 promoters for all species. Furthermore, point mutations of the core sequence caused a marked increase of DMP1 promoter activity in HepG2 and HeLa cells. We speculate that this silencing cis-element may play a critical role in the regulation of DMP1 cell-specific expression.

Base Sequence↗
PubMed2003

Chemocyanin, a small basic protein from the lily stigma, induces pollen tube chemotropism.

In plant reproduction, pollination is an essential process that delivers the sperm through specialized extracellular matrices (ECM) of the pistil to the ovule. Although specific mechanisms of guidance for pollen tubes through the pistil are not known, the female tissues play a critical role in this event. Many studies have documented the existence of diffusible chemotropic factors in the lily stigma that can induce pollen tube chemotropism in vitro, but no molecules have been isolated to date. In this study, we identified a chemotropic compound from the stigma by use of biochemical methods. We purified a lily stigma protein that is active in an in vitro chemotropism assay by using cation exchange, gel filtration, and HPLC. Tryptic digestion of the protein yielded peptides that identified the protein as a plantacyanin (basic blue protein), and this was confirmed by cloning the cDNA from the lily stigma. Plantacyanins are small cell wall proteins of unknown function. The measured molecular mass by electrospray ionization ion source MS is 9898 Da, and the molecular mass of the mature protein (calculated from the cDNA) is 9900.2 Da. Activity of the lily plantacyanin (named chemocyanin) is enhanced in the presence of stigma/stylar cysteine-rich adhesin, previously identified as a pollen tube adhesin in the lily style.

Amino Acid Sequence↗
PubMed2002

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↗