PubMed Health⌕ Search

Biomedical subjects

M Zeichner-David

Publications and source records attributed to M Zeichner-David.

43 records · Page 3Linked to original sources
PubMed1983

Biosynthesis and secretion of enamel proteins during hamster tooth development.

Experiments were designed to detect and determine the biosynthetic behavior of enamel proteins in Syrian Golden hamsters. Enamel matrix proteins were extracted from 3-day-old postnatal first molar tooth organs. Labeling pulse/chase experiments with [35S]-methionine followed by light microscopic autoradiography, or polyacrylamide slab gel electrophoresis and fluorography, showed the synthesis of epithelial-specific gene products. Synthesis and secretion of enamel proteins required approximately 30 min under these in vitro organ culture conditions; both enamelin and amelogenin proteins were synthesized and secreted into the forming extracellular matrix. Amelogenin proteins were secreted initially and rapidly degraded into increasingly smaller polypeptides. In contrast, enamelin proteins were secreted at a slower rate and remained more or less stable over the duration of the experiment. The specific activities of both classes of proteins increased over a 6-hour synthesis period, indicating the accumulation of both proteins into the forming extracellular matrix. Comparisons of the kinetics of formation and posttranslational processing of enamelin and amelogenin are consistent with the presence of possibly two different gene products in hamster secretory ameloblasts.

Amelogenesis↗
PubMed1983

Construction and identification of mouse amelogenin cDNA clones.

The determination of the biochemical phenotype of tooth epithelium requires specification by the dental mesenchyme. This is a general feature of epithelial-mesenchymal interaction in a number of different epidermal organ systems (e.g., salivary gland, mammary gland, feather, skin, and hair morphogenesis). To investigate these developmental processes, we have identified a cDNA clone representing the major group of gene products associated with enamel extracellular matrix formation. The mRNAs for mouse amelogenins, representing approximately equal to 90% of the total enamel proteins, have been isolated and partially characterized by specific immunoprecipitation. The poly(A)-containing RNAs were used for the synthesis and cloning of the mouse amelogenin cDNA. Recombinant plasmids containing amelogenin cDNA sequences were identified by differential hybridization, hybrid-selected translation, and blot hybridization analyses. A cloned sequence was used to identify the expression of amelogenins during tooth development. The mouse cDNA sequence hybridized to genomic mouse and human DNAs. This amelogenin cDNA probe now enables molecular investigations of a number of classical problems in developmental biology.

Amelogenin↗
PubMed1983

Enamelin gene expression during fetal and neonatal rabbit tooth organogenesis.

Epithelial differentiation is a complex process which requires an integrated synthesis of DNA along with synthesis of a full complement of unique mRNAs and their respective proteins characteristic for each cell type. The time of initial transcription of enamel protein mRNAs and subsequent translation of proteins characteristic for secretory ameloblasts is not known. In order to determine when enamel protein mRNAs appear during New Zealand White rabbit molar tooth organogenesis, and when nascent enamel proteins are first translated, we analyzed early cap stages through late crown stages of molar tooth formation (i.e., 21-days gestation through 2-days postnatal). The biochemical phenotype which characterized rabbit ameloblasts were the acidic glycoproteins termed enamelins. Polyclonal antibodies were produced against the major fetal rabbit enamelin of approximately 70,000 daltons. Immunoprecipitation of enamelins from mRNA-directed translation products in a reticulocyte cell-free system, was used to characterize enamelin mRNAs. Enamelin mRNAs were first detected during bell stages (circa 23-days gestation), and persisted till crown stage (circa 28-days gestation). Indirect immunofluorescent localization of enamelin antigen showed staining over the extracellular enamel organ matrix by 23-days gestation. Neither enamelin mRNAs or polypeptides were detected during early or late cap stages of odontogenesis. Transcription of enamelin mRNAs coding for two enamelins of 65 an 58 kd (kilodaltons) appeared to be closely coupled with the translation of these enamel proteins. We assume that close-range ectomesenchyme- derived instructions mediate the biochemical differentiation of ameloblasts between 21-days and 23-days gestation during fetal rabbit development.

Ameloblasts↗
PubMed1982

Enamel gene products during murine amelogenesis in vivo and in vitro.

Epithelial-mesenchymal interactions regulate determination and differentiation of amelogenesis. Our attention has focused on identification of ameloblast gene products, the regulation of enamel mRNA synthesis, and subsequent translation into enamel proteins in vivo and in vitro. Enamel proteins are the most abundant gene products synthesized in fully-differentiated ameloblasts. Our experimental strategy has been to isolate major proteins, produce antibodies, localize enamel protein antigens during tooth development in vivo as well as in vitro (using serumless, chemically-defined medium), develop an immunoprecipitation assay, isolate poly(A)-products in a cell-free translation system, and then initiate molecular cloning of the corresponding murine enamel gene(s). The major murine enamel mRNA appears to code for a predominant polypeptide of approximately 20,000 MW. Inner-enamel epithelial cells differentiate into ameloblasts, and synthesize and secrete enamel proteins within six d when cap-stage molar tooth organs are cultured in serumless, chemically-defined medium. The regulation of epithelial differentiation under these experimental conditions indicates that epithelial-mesenchymal interactions determine and maintian ameloblast differentiation in vitro.

Ameloblasts↗
PubMed1980

Isolation and preliminary characterization of epithelial-specific messenger ribonucleic acids and their products during embryonic tooth development.

Experiments were designed to identify and characterize tissue-specific proteins involved in the process of tooth organogenesis. Epithelial and mesenchymal proteins were extracted from intact molar organs or mechanically separated tissues obtained from 25-day New Zealand White rabbit embryos. Labelling experiments with [35S]methionine followed by radioautography or gel electrophoresis and fluorography showed the presence of label only in epithelial proteins. Most of these proteins range from 43 000 mol.wt. and higher, except for one band of approx. 16 000 mol.wt. A mRNA fraction of 16--26S was isolated by ultracentrifugation on sucrose gradients. When translated in a reticulocyte-lysate cell-free system, the mRNA obtained from intact molar organs resulted in the synthesis of three proteins, of mol.wts. 65 000, 58 000 and 43 000. A similar mRNA fraction obtained from dental-pulp mesenchyme gave only the 43 000-mol.wt. protein, indicating that the 65 000- and 58 000-mol.wt. proteins are derived from epithelial cells.

Ameloblasts↗
PubMedDate not supplied

Presence of dentin phosphoprotein in molars of a patient with dentinogenesis imperfecta type II.

Dentin phosphoprotein (DPP) is the major noncollagenous protein component of the dentin extracellular matrix. This highly acidic phosphorylated protein is solely expressed by the ectomesenchymal-derived odontoblast cells of the tooth organ. Several biochemical studies have suggested diminished levels of, or even the absence of, this protein, which is associated with the human genetic disease dentinogenesis imperfecta (DGI) type II. However, more recent molecular studies have established that the DPP gene locus is not localized to the region of human chromosome 4 (4q13-q21), where several previous linkage analysis studies have mapped DGI types II and III. The purpose of this study was to determine the presence or absence of DPP in the dentition of a patient affected with DGI type II using a sensitive and specific immunodetection method with a polyclonal antibody against mouse DPP. Our results indicate that a 95-kDa protein, immunologically crossreactive with the DPP antibody, was detected within the dentin extracellular matrix of molars isolated from both a proband affected with DGI-II and from an age-matched normal individual. In addition, both DGI-II and normal individuals showed comparable DPP in situ degradation associated with dentin extracellular matrix maturation. These results strongly support the hypothesis that the DPP structural gene does not produce the gene product primarily responsible for the human genetic disease DGI type II.

Adult↗