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P Bringas

Publications and source records attributed to P Bringas.

At least 37 records · Page 2Linked to original sources
PubMed1998

Epithelium-specific adenoviral transfer of a dominant-negative mutant TGF-beta type II receptor stimulates embryonic lung branching morphogenesis in culture and potentiates EGF and PDGF-AA.

Although exogenous transforming growth factor-beta (TGF-beta) is known to inhibit branching morphogenesis in mouse embryonic lungs in culture, whether the principal negative function of endogenous TGF-beta signaling resides in lung epithelium or mesenchyme remains unresolved. A recombinant adenovirus was constructed, containing a mutated human TGF-beta type II receptor with a truncated cytoplasmic kinase domain. We examined whether this dominant-negative receptor could abolish epithelium-specific endogenous TGF-beta signaling. We introduced the recombinant adenovirus into lung explants via intra-tracheal micro-injection. This resulted in over-expression of exogenous truncated TGF-beta type II receptor only in airway epithelium, not in mesenchyme, as assessed by mRNA level and protein localization. Blockade of endogenous TGF-beta receptor signaling in epithelial endoderm by the mutated dominant-negative TGF-beta type II receptor resulted in significant (65%) stimulation of epithelial branching morphogenesis, while exogenous TGF-beta no longer downregulated epithelial PCNA immunoreactivity and surfactant protein C (SP-C) expression. Additionally, the mitogenic responses to epidermal growth factor (EGF) and platelet-derived growth factor, PDGF-AA were potentiated by 33 and 31%, respectively. We conclude that epithelium-specific adenovirus-mediated over-expression of a dominant-negative TGF-beta type II receptor completely and specifically abolished the anti-proliferative effects of both endogenous and exogenous TGF-beta. Therefore, epithelium-specific TGF-beta signaling is sufficient to negatively regulate embryonic lung-branching morphogenesis in culture. We speculate that abrogation of TGF-beta signaling stimulates lung morphogenesis by potentiating the inductive and permissive effects of other endogenous peptide growth factors such as EGF and PDGF-AA.

Adenoviridae↗
PubMed1998

Laminin 2 attachment selects myofibroblasts from fetal mouse lung.

Laminins (LNs) are extracellular matrix glycoproteins that are involved in cell adhesion, proliferation, and differentiation. So far, 11 LN variants (LN1 to LN11) have been described. In the lung, at least six LN variants have been identified. However, only the role of LN1 has been characterized to any extent. In this study, we hypothesized that the LN2 variant may play a role during lung development. We identified, by RT-PCR analysis, that the alpha2-chain mRNA of LN2 is expressed during mouse lung development. LN2 adhesion assays were then performed with cells from fetal mouse lung primary cultures. Our results showed that a specific subpopulation of fetal lung cells that expressed vimentin, alpha-smooth muscle actin, and desmin attached onto LN2, whereas the cells that did not adhere to LN2 as well as the total cell population were able to adhere readily on fibronectin. Cell attachment onto LN2 was inhibited by EDTA. In addition, we demonstrated, by RT-PCR and Western analysis, that the LN2-adherent cells autoexpressed the alpha2-chain of LN2. In the late pseudoglandular period, LN2 was localized by immunohistochemistry in the basement membrane of airways and blood vessels and around mesenchymal cells. We conclude that LN2 is expressed during lung development and that a specific subpopulation of fetal lung mesenchymal cells expressing a myofibroblastic phenotype can be selected by attachment to LN2 in primary culture. These findings lead us to speculate that LN2 may play a key role in the cell biology of myofibroblasts during lung development.

Actins↗
PubMed1998

The Shc 66 and 46 kD isoforms are differentially downregulated at parturition in the fetal mouse lung.

Many of the signaling pathways regulating fetal lung mesenchymal cell proliferation are mediated by the Shc intracellular signaling proteins. Shc is expressed as three isoforms: 52 kD and 46 kD proteins (Shc 52 and Shc 46, respectively) translated from the same mRNA, and a 66 kD form (Shc 66) translated from a separate mRNA. Shc 52 is an activator of Ras and mitogen-activated protein kinase, whereas Shc 66 antagonizes Ras activation. The function of Shc 46 is unclear. We hypothesized that the Shc isoforms are differentially regulated during fetal mouse lung morphogenesis. Relative Shc 66 and Shc 46 protein expression are high until parturition (term = 18.5 d), when a dramatic decrease begins; by postconceptual d 20, relative Shc 66 and Shc 46 expression have fallen by 75 and 69%, respectively. A similar pattern of decreasing Shc 66 mRNA expression in the peripartum period was detected by reverse transcription and competitive polymerase chain reaction during the same period. By isoform-specific immunohistochemistry, Shc 66 is widely distributed in the embryonic lung but becomes restricted to the bronchial smooth muscle and overlying epithelia, periarterial smooth muscle, and the interlobar pleura late in gestation. After parturition, Shc 66 is virtually absent from the lung. All three Shc isoforms are phosphorylated by epidermal growth factor stimulation in fetal lung mesenchymal cells, indicating that Shc 66 is functional in these cells. These data indicate that Shc isoforms are differentially regulated during lung development.

3T3 Cells↗
PubMed1998

Induction of amelogenin and ameloblastin by insulin and insulin-like growth factors (IGF-I and IGF-II) during embryonic mouse tooth development in vitro.

Insulin and insulin-like growth factors (IGF-I and IGF-II) are considered pleiotropic, acting as both mitogen and differentiation factors. Several investigators have demonstrated the expression of insulin, IGFs, their cognate receptors and IGF binding proteins during tooth morphogenesis. Previous work done in our laboratory indicated that exogenous insulin and IGFs induce the accumulation of enamel extracellular matrix on mouse mandibular molars cultured in a serumless, chemically defined medium. In order to determine the level of control of these factors in the induction of enamel biomineralization, we designed experiments to quantitate mRNAs for enamel specific-gene products. Mandibular first molars (MI) obtained from E15 Swiss Webster mice were placed in organ culture in the presence of insulin (1,000 ng/ml), IGF-I (100 ng/ml) or IGF-II (100 ng/ml) for 6, 12 and 18-days. At termination date, the RNA was extracted and the concentration of mRNAs for amelogenin, tuftelin and ameloblastin were determined using a quantitative competitive reverse transcription-polymerase chain reaction (RT-PCR) technique (PCR mimic). Our results showed that after 6-days in culture; treatment with insulin, IGF-I and IGF-II increased the synthesis of amelogenin and ameloblastin. In contrast, the expression of tuftelin mRNA was not affected by either factor. 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. These studies also suggest that the regulatory mechanisms controlling tuftelin gene expression are different than the mechanisms regulating ameloblastin and amelogenin transcription.

Amelogenin↗
PubMed1998

Transgene animal model for protein expression and accumulation into forming enamel.

Understanding the cellular and molecular events that regulate the formation of enamel is a major driving force in efforts to characterize critical events during amelogenesis. It is anticipated that through such an understanding, improvements in prevention, diagnosis and treatment-intervention into heritable and acquired diseases of enamel could be achieved. While knowledge of the precise role of an enamel-specific protein in directing the formation of inorganic crystallites remains refractory, progress has been made with other aspects of amelogenesis that can be brought to bear on the subject. One such area of progress has been with the identification of an ameloblast-lineage specific amelogenin gene promoter. This promoter can be used to direct the expression of enamel-specific proteins, as well as the expression of proteins foreign to amelogenesis, into the enamel extracellular matrix where their effect on biomineralization can be ascertained in a prospective manner. The resulting enamel from such animals can be examined by morphologic and biochemical modalities in order to identify the effect of the transgene protein on enamel crystallite formation and subsequent biomineralization. This manuscript outlines such a strategy with the potential for enhancing our understanding of amelogenesis.

Ameloblasts↗
PubMed1998

A mouse mandibular culture model permits the study of neural crest cell migration and tooth development.

A major issue in developmental biology is to determine how time and position-restricted instructions are signaled and received during morphogenesis of different phenotypes, of which tooth, Meckel's cartilage and tongue formation are classical examples. It is now evident that a hierarchy of growth factors and their downstream transcription factors regulate the timing, sequence and position of cells and tissues in forming different phenotypes during embryogenesis. Here we report the development of an early mandibular organ culture model. Explants of E8 and E9 first branchial arch were cultured and produced mandibular processes with cap stage tooth formation, Meckel's cartilage and tongue development. In tandem, vital dye (Dil) labeling studies confirmed that rhombomeres 1-4 give rise to craneal neural crest (CNC) cells which emigrate from the neural fold to the forming maxillary and mandibular arches. Furthermore, we have tested the feasibility of investigating the regulation of different phenotypes within the first branchial arch by a transcription factor using this early mandibular organ culture model. Lymphoid enhancing factor 1 (Lef1), a transcription factor, has been implicated to regulate tooth formation in vivo. We have analyzed the expression of Lef1 and studied the biological effects of Lef1 on E8 embryonic mouse first branchial arch explants in organ culture. Collectively, these results demonstrate that first branchial arch explant model is suitable for studies of rhombencephalic crest cell fate during mandibular morphogenesis and can be used as a model with direct access to investigate the molecular mechanism in regulating first branchial arch morphogenesis.

Animals↗
PubMed1997

Characterization of the fate of midline epithelial cells during the fusion of mandibular prominences in vivo.

The fusion of the mandibular prominences along the midline is achieved with the absence of medial epithelial cells at the fusion site. Failure of fusion of the mandibular prominences results in median cleft of the lower lip and mandible. Cellular and molecular events controlling mandibular fusion were examined during the fusion process in mouse embryogenesis. Cell lineage analyses at the fusion site revealed that epithelial cells migrated to the surface and oral epithelia. DiI-labeled epithelial cells were not observed within the mandibular mesenchyme at any state of fusion. Examination of the midline region did not reveal cells with ultrastructural changes characteristic of apoptotic cell death. An increase in lysosomal enzymes in the midline epithelial cells, which would be correlated with programmed cell death, was not observed. Mice lacking TGF-beta 3 did not have cleft mandible, but had clefting of the secondary palate as a feature of null mutation phenotype. We interpret our comparisons between wild type and homozygous TGF-beta 3 (-/-) mice to suggest that different developmental processes control palatal vs. mandibular fusion. We hypothesize that medical epithelial cells at the fusion site of mandibular prominences migrate to the surface epithelium during the fusion process and neither transdifferentiate into mesenchyme nor express apoptosis.

Animals↗
PubMed1997

TGF-alpha, EGF, and their cognate EGF receptor are co-expressed with desmin during embryonic, fetal, and neonatal myogenesis in mouse tongue development.

The developing mouse tongue provides a model for discrete patterns of morphogenesis during short periods of embryonic development. Occipital somite-derived myogenic cells interact with cranial neural crest-derived ecto-mesenchymal cells to form the musculature of the tongue. The biochemical signals that control close range autocrine and/or paracrine signaling processes required to establish the fast-twitch complex tongue musculature are not known. The present study was designed to test the hypothesis that desmin, epidermal growth factor (EGF), and transforming growth factor-alpha (TGF alpha) and their cognate receptor, epidermal growth factor receptor (EGFr), are co-expressed during tongue myogenesis and define specific developmental stages of tongue muscle cell differentiation. To test this hypothesis, we performed studies to analyze the timing, position, and concentration of desmin, TGF alpha, EGF, and EGFr from embryonic day 9 (E9) through birth in Swiss Webster mouse tongue development. Desmin, TGF alpha, EGF, and EGFr co-localized to cells of myogenic lineage in the four occipital somites and subsequently in myoblasts and myotubes from E9 through E17. By newborn stage, desmin is localized to discrete regions in myofibers corresponding to Z-line delimiting sarcomeres, and A-band within sarcomeres; immunostaining for desmin, TGF alpha, and EGF persisted in differentiated myotubes and striated skeletal muscle. Desmin increased from 0.01% at E11 to 0.51% of the total protein by E17 and at birth. Concomitantly, the patterns and increases in TGF alpha, EGF, and EGFr showed significant increases during the same developmental period. The temporal and positional co-localization of TGF alpha, EGF, and EGFr support the hypothesis that autocrine and paracrine regulation of desmin by actions of growth factor ligand and receptor defines critical stages of tongue myogenesis.

Animals↗
PubMed1996

Co-culture of contiguous developmental fields in a serumless, chemically-defined medium: an in vitro model permissive for coordinate development of the mouse ear.

Pattern formation is intrinsically hierarchical, increasing in complexity from the first early embryonic inductive tissue interactions to the eventual integration of multiple organ systems. Viewed as a problem in pattern formation, the vertebrate ear is an exceedingly complex organ system in which normal morphogenesis requires multiple inductive interactions between a variety of adjacent tissues. In order to model the process of higher level pattern formation, we have developed a method for organ culture of the embryonic murine ear. E10.5 mouse embryos (38 to 42 somite pairs) were microdissected into explants that consist of the first and second branchial arches, the otocyst, and the adjacent neural tube. The growth of these explants in a serumless, chemically-defined medium was compared to medium supplemented with 10% fetal calf serum. After 6 days in culture using serumless medium, we observed that this environment was permissive for the formation of pinnae, rudimentary semicircular canals and cochlear ducts, chondrogenesis of the otic capsule and elongation of the endolymphatic ducts. Posterior elements of Meckel's and Reichert's cartilages were identified as ossicular anlagen. All of these structures maintained appropriate anatomic interrelationships during in vitro development. Furthermore, no significant differences were observed in explants grown in serum-supplemented medium. We conclude that during ear development several histogenetic and morphogenetic processes, including aspects of higher level pattern formation, are mediated primarily by paracrine and/or autocrine factors. The development of an organ culture model using serumless medium should facilitate the discovery of intrinsic factors which regulate the coordinate development of inner, middle and external ear structures.

Animals↗
PubMed1995

Effects of flumethrin on hepatic drug-metabolizing enzymes and antipyrine disposition in rats.

The effects of repeated exposure to the pyrethroid insecticide flumethrin (40 mg/kg intraperitoneally once a day for 6 days) on the activity of cytochrome P450-dependent monooxygenases and UDP-glucuronosyltransferase as well as on antipyrine disposition were investigated in male Wistar rats. Pretreatment with flumethrin decreased the activities of NADPH-cytochrome c reductase (38%), aniline hydroxylase (53%), aminopyrine N-demethylase (54%), and UDP-glucuronosyltransferase (34%), and the content of cytochrome P450 (36%) in hepatic microsomes. Total plasma clearance of antipyrine was decreased by flumethrin pretreatment (54%), while the elimination half-life at beta phase and the mean residence time of antipyrine were increased (96 and 88%, respectively). Urinary excretion of norantipyrine, 4-hydroxyantipyrine, and 3-hydroxymethylantipyrine was decreased by 60, 38, and 33%, respectively, in the 96 hr after flumethrin treatment. In addition, the rate constants for formation of each of these metabolites were decreased by an average of approximately 74%. These findings provide evidence that flumethrin exposure diminishes hepatic enzyme levels and catalytic activities of monooxygenase systems as well as oxidative metabolism of antipyrine.

Animals↗
PubMed1995

Pharmacokinetics and residues of enrofloxacin in chickens.

The pharmacokinetic properties of enrofloxacin were determined in broiler chickens after single IV and orally administered doses of 10 mg/kg of body weight. After IV and oral administrations, the plasma concentration-time graph was characteristic of a two-compartment open model. The elimination half-life and the mean +/- SEM residence time of enrofloxacin for plasma were 10.29 +/- 0.45 and 9.65 +/- 0.48 hours, respectively, after IV administration and 14.23 +/- 0.46 and 15.30 +/- 0.53 hours, respectively, after oral administration. After single oral administration, enrofloxacin was absorbed slowly, with time to reach maximal plasma concentration of 1.64 +/- 0.04 hours. Maximal plasma concentration was 2.44 +/- 0.06 micrograms/ml. Oral bioavailability was found to be 64.0 +/- 0.2%. Statistically significant differences between the 2 routes of administration were found for the pharmacokinetic variables--half-lives of the distribution and elimination phase and apparent volume of distribution and volume of distribution at steady state. In chickens, enrofloxacin was extensively metabolized into ciprofloxacin. Residues of enrofloxacin and the major metabolite ciprofloxacin in fat, kidney, liver, lungs, muscles, and skin were measured in chickens that received an orally administered dose of 10 mg/kg once daily for 4 days. The results indicate that enrofloxacin and ciprofloxacin residues were cleared slowly. Mean muscle, liver, and kidney concentrations of the metabolite ciprofloxacin ranging between 0.020 and 0.075 micrograms/g persisted on day 12 in chickens after dosing. However, at the time of slaughter (12 days), enrofloxacin residues were only detected in liver and mean +/- SEM concentration was 0.025 +/- 0.003 micrograms/g.

Administration, Oral↗
PubMed1994

Translocation of enamel proteins from inner enamel epithelia to odontoblasts during mouse tooth development.

The developmental problem of how dental epithelia and/or dental papilla ectomesenchyme induce and/or up- or down-regulate tooth formation are as yet unresolved issues. We have designed studies to map the synthesis and fate pathways of secreted amelogenin proteins from Kallenbach differentiation zones II-IV during in vivo and in vitro mouse mandibular first molar tooth development (M1). Tooth organs from cap, bell, and crown stages were processed for reverse transcriptase/polymerase chain reaction (RT-PCR) and high resolution Protein A immunocytochemistry using anti-amelogenin and anti-peptide antibodies. Cap stage M1 were cultured for periods ranging from 10-21 days in vitro using either serum-less, or 15% fetal calf sera-supplemented, chemically-defined medium. Amelogenin transcripts are expressed in the mouse embryonic molar from E15 through early postnatal development. Amelogenin antigens were first detected in Kallenbach's differentiation zone II. Amelogenin proteins secreted from preameloblasts were identified along cell processes and cell surfaces of odontoblasts adjacent to forming mantle dentine extracellular matrix (ECM) prior to biomineralization. Amelogenin proteins were restricted to forming endocytotic vesicles, clathrin-coated vesicles, and lysosomes within odontoblasts. At later stages (e.g. 2 days postnatal development), enamel proteins were not identified in odontoblasts or predentine matrix following mineralization. Comparable observations for stages of development were noted for in vitro cultured tooth explants. Preameloblasts synthesize and secrete amelogenin proteins which bind to odontoblast cell surfaces possibly through the process of receptor-mediated endocytosis. We conclude that amelogenin proteins secreted from preameloblasts, prior to the initiation of biomineralization, were translocated to odontoblasts to serve as yet unknown biological functions.

Amelogenin↗
PubMed1994

Specific transforming growth factor-beta subtypes regulate embryonic mouse Meckel's cartilage and tooth development.

Members of the transforming growth factor-beta (TGF-beta) superfamily have emerged as critical regulators for cell growth and differentiation. Whereas the different TGF-beta subtypes are equipotent in the majority of biological assays using cell lines cultured in vitro, there are indications that in more complex systems involving epithelial-mesenchymal interactions, the TGF-beta subtypes differ in their biological activities. To test the hypothesis that TGF-beta subtypes specifically regulate either Meckel's cartilage or tooth morphogenesis, we designed experiments to compare loss of function effects of TGF-beta 1, TGF-beta 2, and TGF-beta 3 subtypes using a serumless, chemically defined medium to culture embryonic mouse E10 (42-44 somite pairs) mandibular explants. The major effect of loss of function resulting from abrogation of TGF-beta 1 using antisense treatment resulted in a 20% increase (P < 0.05) in chondrocyte number, a decrease in extracellular matrix, and dysmorphology of the rostral region of Meckel's cartilage. Exogenous TGF-beta 1 provided indistinguishable recovery to the normal phenotype. TGF-beta 2 antisense treatment produced a threefold enlargement (P < 0.05) of tooth organs and advanced their development to the cap stage. TGF-beta 2 provided recovery to the normal phenotype (e.g., reduced tooth size and development to the bud stage), whereas TGF-beta 1 or TGF-beta 3 polypeptides had no effect. TGF-beta 3 antisense treatment resulted in a reduction of approximately 15% in the length of Meckel's cartilage. We interpret these results to suggest that TGF-beta 1 functions to regulate the number of chondrogenic cells, the amount of extracellular matrix, and the rate of developmental assembly of the rostral to posterior segments in forming Meckel's cartilage. TGF-beta 2 appears to regulate tooth size and stage of development without affecting cartilage. TGF-beta 3 appears to regulate Meckel's cartilage size without altering tooth size or shape. The results are discussed in terms of the regulatory functions of the TGF-beta subtypes during embryonic craniofacial morphogenesis.

Animals↗
PubMed1994

Bioavailability, pharmacokinetics and residues of chloramphenicol in the chicken.

The pharmacokinetic properties of chloramphenicol were determined in broiler chickens after two single oral doses (30 and 50 mg/kg body weight) and after a single intravenous (i.v.) dose (30 mg/kg body weight). After oral and i.v. administration, the plasma concentration-time graph was characteristic of a two-compartment open model. After oral administration (30 and 50 mg/kg), chloramphenicol was absorbed rapidly (time to maximal concentration of 0.72 or 0.60 h) and eliminated with a mean half-life (t1/2 beta) of 6.87 or 7.41 h, respectively. The bioavailability was 29% at 30 mg/kg chloramphenicol and 38% at 50 mg/kg chloramphenicol. Concentrations greater than 5 micrograms/ml were achieved at 15 min and persisted up to 2 or 4 h post-administration, respectively. Statistically significant differences between the two routes of administration were found for the pharmacokinetic variables, half-lives of both distribution and elimination phases (t1/2 alpha, t1/2 beta) and apparent volume of distribution [Vd(area)]. The mean t1/2 beta of chloramphenicol and i.v. administration was 5.23 h. Chloramphenicol was extensively metabolized into dehydrochloramphenicol (DH-CAP), nitrophenylaminopropanedione (NPAP) and nitroso-chloramphenicol (NO-CAP) derivatives. Residues of chloramphenicol (CAP) and the three metabolites DH-CAP, NPAP and NO-CAP in kidney, liver and muscle were measured in chickens that received an oral dose of 50 mg/kg once daily for 4 days. The results indicate that CAP and DH-CAP residues were cleared slowly and were at or below the detection limit of 0.005 microgram/ml within 12 days after dosing. However, at the time of slaughter (12 days), the NPAP and NO-CAP residues were detected in the tissue.

Administration, Oral↗
PubMed1993

Endogenous epidermal growth factor regulates limb development.

Mutations associated with genes of the EGF superfamily are implicated in limb malformations. To evaluate the potential role of EGF-mediated signal transduction in the control of early mammalian limb development, we developed a simple in vitro system which is permissive for morphogenesis and cytodifferentiation in serumless, chemically defined medium. Our experimental strategy was to ascertain if the EGF precursor gene was transcribed and translated into potentially bioactive growth factor. EGF mRNA transcripts are expressed in Swiss Webster mouse embryonic (42-44 somite pairs) forelimbs as determined by mRNA phenotyping. EGF transcripts are translated into precursor EGF polypeptides which were localized to limb covering epithelium and the chondrogenic mesenchymal cell lineages. EGF immunostaining patterns suggested a paracrine type of regulation for the cartilage blastema associated with forelimb development. To test whether EGF effects the timing and positional information required for limb-specific cartilage morphogenesis, we employed tyrphostin (RG 50864) which inhibits EGF receptor kinase activity in a concentration-dependent manner and severely retards limb development. These findings support our hypothesis that endogenous EGF or EGF-like proteins provide signaling for the size and shape of discrete forelimb cartilage formations during mouse embryonic morphogenesis.

Animals↗
PubMed1993

Antisense inhibition of AMEL translation demonstrates supramolecular controls for enamel HAP crystal growth during embryonic mouse molar development.

During tooth development, enamel organ epithelial cells express a tissue-specific gene product (amelogenin) which presumably functions to control calcium hydroxyapatite crystal growth patterns during enamel biomineralization. The present studies were designed to test the hypothesis that amelogenin as a supramolecular aggregate regulates crystal growth during enamel biomineralization. Antisense oligodeoxynucleotide strategy was used in a simple organ culture system to inhibit amelogenin translation. Under these experimental conditions, antisense treatment prior to and during amelogenin expression resulted in inhibition of amelogenin translation products within immunoprecipitated [35S]methionine metabolically labeled proteins. To determine the efficiency of antisense treatment in this model system, digoxigenin-labeled oligodeoxynucleotides were observed to diffuse throughout the tooth explants including the target ameloblast cells within 24 hours. Ultrastructural analyses of amelogenin supramolecular assembly as electron-dense stippled materials in antisense treated cultures demonstrated dysmorphology of the extracellular enamel matrix with a significant reduction in crystal length and width. We conclude that secreted extracellular proteins form a supramolecular aggregate, which controls both the orientation and dimensions of enamel crystal formation during tooth development.

Amelogenesis↗
PubMed1993

EGF abrogation-induced fusilli-form dysmorphogenesis of Meckel's cartilage during embryonic mouse mandibular morphogenesis in vitro.

Mutations associated with genes of the EGF superfamily are implicated in facial malformations arising from abnormal development of the first branchial arch. EGF and EGF receptor (EGFr) transcripts are expressed in the mouse embryonic first branchial arch and derivatives from E9 through E15. EGF transcripts are localized to ectomesenchymal cells associated with precartilage, cartilage, bone and tooth-forming cells. EGF and EGFr proteins co-localize to the same cells suggesting an autocrine regulation. To test whether EGF effects the timing and positional information required for Meckel's cartilage (MC) and tooth development, we cultured E10 mandibular explants in serumless, chemically defined medium with either antisense or sense EGF oligodeoxynucleotides. Antisense inhibition of EGF expression produces bilaterally symmetrical Fusilli-form dysmorphogenesis of MC and decreases tooth bud size; these effects are reversed by the addition of exogenous EGF to the culture medium. Tyrphostin RG 50864, which inhibits EGF receptor kinase activity, inhibits EGF stimulation of tyrosine phosphorylation in a concentration-dependent manner and severely retards mandibular development yet increases tooth size. These findings support the hypothesis that endogenous EGF and EGF-like proteins provide signalling to regulate the size and shape both of cartilage and tooth formation during craniofacial morphogenesis.

Animals↗