[Mandibular fibrous dysplasia: a monostotic form]. / Dysplasie fibreuse mandibulaire : une forme monostotique.

INTRODUCTION: The onset of one or several diastema in adults with no link of etiology to tooth loss or to a periodontal problem can be the first evocative sign of an acromegaly or a benign or malignant tumoral process. OBSERVATION: A 40-year-old patient consulted for an implant to solve an esthetic problem caused by a diastema. The complementary exams revealed an osteolytic lesion marked by condensing areas. The biopsy proved the diagnosis of fibrous dysplasia. DISCUSSION: Etiologies of fibrous dysplasia are varied. They can be related to a congenital defect of osteo mesenchyma development or be the consequence of trauma, reaction to infection, or an endocrine or metabolic disorder.

[Vertical alveolar distraction osteogenesis of the posterior edentulous mandible: a case report]. / Distraction alvéolaire des secteurs postérieurs mandibulaires: à propos d'un cas clinique.

When it is necessary to increase the vertical height of the residual alveolar ridge, alveolar distraction osteogenesis has numerous advantages compared to other preprosthetic surgical procedures. It is frequently used for this purpose in the anterior region because of the obvious accessibility. The authors present a clinical case of edentulous posterior mandible, with insufficient vertical alveolar bone height, treated by alveolar distraction osteogenesis leading to three titanium fixtures. They explain their choice and discuss the preliminary results.

[Malignant lymphoma of the mandible. A new case]. / Lymphome malin de la mandibule. A propos d'un nouveau cas.

Primary extranodal malignant lymphoma is relatively rare. Clinical and radiological features may lead to the misdiagnosis of chronic osteomyelitis. We report a case of primary non-Hodgkin's lymphoma that involved the mandibular region in a 53-year-old man. Differential diagnosis with other mandibular diseases is difficult because there is a non specific clinico-radiological features and the difficulty of histologic interpretation. This pathology is important to recognize because of specific treatment. Global prognosis is relatively favorable if the lesion is localized.

Nuclear import of activated D-ERK by DIM-7, an importin family member encoded by the gene moleskin.

The initiation of gene expression in response to Drosophila receptor tyrosine kinase signaling requires the nuclear import of the MAP kinase, D-ERK. However, the molecular details of D-ERK translocation are largely unknown. In this regard, we have identified D-Importin-7 (DIM-7), the Drosophila homolog of vertebrate importin 7, and its gene moleskin. DIM-7 exhibits a dynamic nuclear localization pattern that overlaps the spatial and temporal profile of nuclear, activated D-ERK. Co-immunoprecipitation experiments show that DIM-7 associates with phosphorylated D-ERK in Drosophila S2 cells. Furthermore, moleskin mutations enhance hypomorphic and suppress hypermorphic D-ERK mutant phenotypes. Deletion or mutation of moleskin dramatically reduces the nuclear localization of activated D-ERK. Directly linking DIM-7 to its nuclear import, this defect can be rescued by the expression of wild-type DIM-7. Mutations in the Drosophila Importin beta homolog Ketel, also reduce the nuclear localization of activated D-ERK. Together, these data indicate that DIM-7 and Ketel are components of the nuclear import machinery for activated D-ERK.

Delayed wound repair and impaired angiogenesis in mice lacking syndecan-4.

The syndecans make up a family of transmembrane heparan sulfate proteoglycans that act as coreceptors with integrins and growth factor tyrosine kinase receptors. Syndecan-4 is upregulated in skin dermis after wounding, and, in cultured fibroblasts adherent to the ECM protein fibronectin, this proteoglycan signals cooperatively with beta1 integrins. In this study, we generated mice in which the syndecan-4 gene was disrupted by homologous recombination in embryonic stem cells to test the hypothesis that syndecan-4 contributes to wound repair. Mice heterozygous or homozygous for the disrupted syndecan-4 gene are viable, fertile, and macroscopically indistinguishable from wild-type littermates. Compared with wild-type littermates, mice heterozygous or homozygous for the disrupted gene have statistically significant delayed healing of skin wounds and impaired angiogenesis in the granulation tissue. These results indicate that syndecan-4 is an important cell-surface receptor in wound healing and angiogenesis and that syndecan-4 is haplo-insufficient in these processes.

Syndesmos, a protein that interacts with the cytoplasmic domain of syndecan-4, mediates cell spreading and actin cytoskeletal organization.

Syndecan-4 is a cell surface heparan sulfate proteoglycan which, in cooperation with integrins, transduces signals for the assembly of focal adhesions and actin stress fibers in cells plated on fibronectin. The regulation of these cellular events is proposed to occur, in part, through the interaction of the cytoplasmic domains of these transmembrane receptors with intracellular proteins. To identify potential intracellular proteins that interact with the cytoplasmic domain of syndecan-4, we carried out a yeast two-hybrid screen in which the cytoplasmic domain of syndecan-4 was used as bait. As a result of this screen, we have identified a novel cellular protein that interacts with the cytoplasmic domain of syndecan-4 but not with those of the other three syndecan family members. The interaction involves both the membrane proximal and variable central regions of the cytoplasmic domain. We have named this cDNA and encoded protein syndesmos. Syndesmos is ubiquitously expressed and can be myristylated. Consistent with its myristylation and syndecan-4 association, syndesmos colocalizes with syndecan-4 in the ventral plasma membranes of cells plated on fibronectin. When overexpressed in NIH 3T3 cells, syndesmos enhances cell spreading, actin stress fiber and focal contact formation in a serum-independent manner.

Syndecan-4 signals cooperatively with integrins in a Rho-dependent manner in the assembly of focal adhesions and actin stress fibers.

The assembly of focal adhesions and actin stress fibers by cells plated on fibronectin depends on adhesion-mediated signals involving both integrins and cell-surface heparan sulfate proteoglycans. These two cell-surface receptors interact with different domains of fibronectin. To attempt to identify the heparan sulfate proteoglycans involved, we used fibronectin-null (FN-/-) mouse fibroblasts to eliminate the contribution of endogenous fibronectin during the analysis. FN-/- fibroblasts plated on the cell-binding domain of fibronectin or on antibodies directed against mouse beta1 integrin chains attach but fail to spread and do not form focal adhesions or actin stress fibers. When such cells are treated with antibodies directed against the ectodomain of mouse syndecan-4, they spread fully and assemble focal adhesions and actin stress fibers indistinguishable from those seen in cells plated on intact fibronectin. These results identify syndecan-4 as a heparan sulfate proteoglycan involved in the assembly process. The antibody-stimulated assembly of focal adhesions and actin stress fibers in cells plated on the cell-binding domain of fibronectin can be blocked with C3 exotransferase, an inhibitor of the small GTP-binding protein Rho. Treatment of cells with lysophosphatidic acid, which activates Rho, results in full spreading and assembly of focal adhesions and actin stress fibers in fibroblasts plated on the cell-binding domain of fibronectin. We conclude that syndecan-4 and integrins can act cooperatively in generating signals for cell spreading and for the assembly of focal adhesions and actin stress fibers. We conclude further that these joint signals are regulated in a Rho-dependent manner.

Rek, a gene expressed in retina and brain, encodes a receptor tyrosine kinase of the Axl/Tyro3 family.

Rek (retina-expressed kinase) has been identified as a putative novel receptor-type tyrosine kinase of the Axl/Tyro3 family with a potential role in neural cell development. rek clones were isolated from a chick embryonic brain cDNA library with a DNA probe obtained by reverse transcriptase-polymerase chain reaction of mRNA from Müller glia-like cells cultured from chick embryonic retina. Sequence analysis indicated that Rek is a protein of 873 amino acids with an extracellular region composed of two immunoglobulin-like domains followed by two fibronectin type III domains with eight predicted N-glycosylation sites. Two consensus src homology 2 domain binding sites are present in the cytoplasmic domain, suggesting that Rek activates several signal transduction pathways. Northern analysis of rek mRNA revealed a 5.5-kilobase transcript in chick brain, retina, and kidney and in primary cultures of retinal Müller glia-like cells. Rek protein was identified by immunoprecipitation and immunoblotting as a 140-kDa protein expressed in the chick retina at embryonic days 6-13, which corresponded to the major period of neuronal and glial differentiation. Transfection of rek cDNA into COS cells resulted in transient expression of a putative precursor of 106 kDa that autophosphorylated in immune complex protein kinase assays. Overexpression of rek cDNA in mouse NIH3T3 fibroblasts resulted in activation of the 140-kDa rek kinase and induction of morphologically transformed foci. These properties indicated that Rek has oncogenic potential when overexpressed, but its normal function is likely to be related to cell-cell recognition events governing the differentiation or proliferation of neural cells.

Structure and organization of the mouse elk1 gene.

In the ets gene family of transcription factors, elk1 belongs to the subfamily of Ternary Complex Factors (TCFs) which bind to the Serum Response Element (SRE) in conjunction with a dimer of Serum Response Factors (SRFs). In this communication we report the isolation of cDNAs from the mouse elk1 gene, containing the full coding sequence homologous (87% identical) to the human gene, and the structure and organization of 22 kb of the mouse elk1 locus. The coding sequence is spread through 5 exons (numbered 1 to 5): exons 1 to 4 range from 102 bp to 447 bp and exon 5 is at least 620 bp. Exon 0 was not found in the 8.5 kb sequence upstream of exon 1. The intron between exons 1 and 2 is 4 kb long and the 3 other introns are less than 500 bp long. This information will be useful to engineer targeted mutations of this gene in mice and to determine the genomic structure of the other TCF genes.

Characterization of a new melanocyte-specific gene (QNR-71) expressed in v-myc-transformed quail neuroretina.

Quail neuroretina cells (QNR) infected with the v-myc-expressing retrovirus MC29 become pigmented after several passages in vitro. After differential screening of a cDNA library constructed from these cells, we have isolated a cDNA clone (QNR-71) which identifies an RNA expressed only in the pigmented layer of the retina and in the epidermis. This gene can also be induced in other cell types transformed by MC29, suggesting that QNR-71 may be regulated by the v-myc protein. Sequence analysis showed that the QNR-71 cDNA exhibits stretches of homologies with melanosomal proteins encoding genes. From bacterially expressed QNR-71 peptides we obtained rabbit antisera able to specifically recognize two proteins of 95 and 100 kDa in pigmented retinal cells, but not in the neuroretina. To study the regulation of QNR-71, we used promoter fragments linked to the CAT reporter gene, in transient co-expression assay. We observed an increase in CAT expression with a c-MYC and microphtalmia (mi) expression vectors. Both MYC and mi activate the QNR-71 promoter through direct binding to a CATGTG site present in the promoter fragment.

Conservation of regulated alternative splicing and identification of functional domains in vertebrate homologs to the Drosophila splicing regulator, suppressor-of-white-apricot.

Although several splicing regulatory proteins have been identified in Drosophila through characterization of various genetic mutations, including sex-lethal, transformer, transformer-2, suppressor-of-white-apricot (su(wa)), and possibly suppressor-of-sable, none of these have been identified in vertebrates. We describe the cloning and characterization of human (HsSWAP) and mouse (MmSWAP) homologs of the su(wa) gene. Comparison of the Drosophila and mammalian proteins reveals five highly homologous regions, including an arginine/serine-rich domain and two repeated modules that are homologous to regions in the constitutive splicing factor, SPP91/PRP21. These modules thus define a new motif likely important in the regulatory and constitutive splicing functions of these proteins. The Drosophila su(wa) gene autoregulates its expression by control of splicing of its first two introns. Comparison of mammalian and Drosophila SWAP mRNAs revealed that the splice junctions of these regulated introns are precisely conserved, showing definitively that these genes are ancestrally related. Moreover, mammalian SWAP mRNAs are also alternatively spliced at the same splice sites, showing that mammalian SWAP expression is regulated (presumably autogenously) by control of splicing of these two introns. These several structural features therefore strongly suggest that the mammalian SWAP gene functions as a vertebrate alternative splicing regulator.

Sequence specific protein binding to and activation of the TGF-beta 3 promoter through a repeated TCCC motif.

We have previously characterized the TGF-beta 3 promoter and shown that the activity of this promoter is highly variable in different cell types. Although the promoter contains a proximal cAMP responsive element, which is critical to basal and forskolin-induced promoter activity, this element is not responsible for the variable, cell-specific regulation of the promoter. In this paper, we identify a 25 base pair sequence in the proximal region of the TGF-beta 3 promoter that binds a novel DNA-binding protein. This region includes the sequence T-CCCTCCCTCCC, (3 x TCCC), and mutation of these T-CCC repeats inhibits protein binding. Further, we show that in the cell line A375, which we have previously shown expresses high levels of TGF-beta 3 mRNA, this region is responsible for mediating high level TGF-beta 3 promoter activity. Immediately 3' to the 3 x TCCC sequence is a consensus AP-2 binding site, however, we show that this region does not bind AP-2, and AP-2 does not transactivate the TGF-beta 3 promoter. Therefore, we provide strong evidence that high level expression of TGF-beta 3 in A375 cells results from transactivation of the TGF-beta 3 promoter by a protein that binds to a repeated TCCC motif in the promoter and suggest that this DNA-binding protein likely also regulates aspects of developmental and tissue-specific expression of this cytokine.

Embryonic gene expression patterns of TGF beta 1, beta 2 and beta 3 suggest different developmental functions in vivo.

We have compared the expression of the genes encoding transforming growth factors beta 1, beta 2 and beta 3 during mouse embryogenesis from 9.5 to 16.5 days p.c. using in situ hybridisation to cellular RNAs. Each gene has a different expression pattern, which gives some indication of possible biological function in vivo. All three genes appear to be involved in chondroossification, though each is expressed in a different cell type. Transcripts of each gene are also present in embryonic epithelia. Epithelial expression of TGF beta 1, beta 2 and beta 3 RNA is associated with regions of active morphogenesis involving epithelial-mesenchymal interactions. In addition, widespread epithelial expression of TGF beta 2 RNA can be correlated with epithelial differentiation per se. The localisation of TGF beta 2 RNA in neuronal tissue might also be correlated with differentiation. Finally both TGF beta 1 and beta 2 transcripts are seen in regions actively undergoing cardiac septation and valve formation, suggesting some interaction of these growth factors in this developmental process.

Differential expression of TGF beta isoforms in murine palatogenesis.

We have studied the expression of genes encoding transforming growth factors (TGFs) beta 1, beta 2 and beta 3 during development of the secondary palate in the mouse from 11.5 to 15.5 days postcoitum using in situ hybridisation. The RNA detected at the earliest developmental stage is TGF beta 3, which is localised in the epithelial component of the vertical palatal shelf. This expression continues in the horizontal palatal shelf, predominantly in the medial edge epithelium, and is lost as the epithelial seam disrupts, soon after palatal shelf fusion. TGF beta 1 RNA is expressed with the same epithelial pattern as TGF beta 3, but is not detectable until the horizontal palatal shelf stage. TGF beta 2 RNA is localised to the palatal mesenchyme underlying the medial edge epithelia in the horizontal shelves and in the early postfusion palate. The temporal and spatial distribution of TGF beta 1, beta 2 and beta 3 RNAs in the developing palate, together with a knowledge of in vitro TGF beta biological activities, suggests an important role for TGF beta isoforms in this developmental process.

Cloning by polymerase chain reaction of a new mouse TGF-beta, mTGF-beta 3.

Two TGF-beta s, TGF-beta 1 and 2, have previously been isolated from the mouse. Here we report the isolation of a murine TGF-beta 3 cDNA. RNAs extracted from 15-day-old mouse embryos and several mouse cell lines were reverse-transcribed. These cDNA mixtures were used as substrates for polymerase chain-reaction amplifications, using oligonucleotides designed on the basis of known human and chicken TGF-beta 3 sequences, including the initiation and stop codons. Several overlapping cDNAs containing either the amino-terminal domain or the carboxy-terminal domain, as well as the complete 1.2-kb coding region of the mouse TGF-beta 3 cDNA were obtained. The mouse TGF-beta 3 coding region is 1230 nucleotides long and codes for a 410 amino acid polypeptide very similar to its human counterpart. This cDNA hybridizes to a unique 3.5-kb RNA and is differentially expressed in various mouse tissues and at different embryonic stages.

Activation of the second promoter of the transforming growth factor-beta 1 gene by transforming growth factor-beta 1 and phorbol ester occurs through the same target sequences.

Two distinct regions of the transforming growth factor-beta 1 (TGF-beta 1) promoter are responsive to autoregulation and activation by phorbol ester (12-O-tetradecanoylphorbol-13-acetate): sequences located between nucleotides -454 to -323 (first promoter) and between the two transcriptional start sites. We have now characterized in detail the induction of the second promoter (sequences between nucleotides + 1 to +271) of the TGF-beta 1 gene by both TGF-beta 1 and phorbol ester. By assaying progressively deleted mutations in the second promoter, we have found two regions responsible for the induction; each contains a phorbol ester-responsive element. In vitro transcription of the second promoter-chloramphenicol acetyltransferase chimeric genes using nuclear extracts of A-549 cells showed that deletion of the putative phorbol ester-responsive elements results in a 70-80% decrease in activity. DNase I footprinting and gel mobility shift assays showed that binding to an Sp1 site and the putative TRE elements are required for maximal expression of the second promoter region of the TGF-beta 1 gene. These results suggest that AP-1, which is capable of conferring phorbol ester or TGF-beta 1 responsiveness, is the major transcription factor involved in the second promoter-derived transcription of the TGF-beta 1 gene.

An invariant asparagine residue belonging to a highly conserved domain in all protein kinases is instrumental in the protein kinase activity of the v-mil gene product.

P100gag-mil, the translation product of the v-mil oncogene of MH2 is a protein kinase specific of serine/threonine residues. We report here that the P100gag-mil encoded by the MH2-Hd isolate displays a considerably reduced kinase activity in vitro. Construction of chimeric viruses and sequencing revealed that the lesion responsible for this reduced activity results from a single point mutation converting an asparagine residue at position 720 in fully active P100gag-mil kinase into serine in the P100gag-mil of MH2-Hd. Since this asparagine residue together with an invariant aspartate residue bracket a highly conserved 6 amino-acid region in all known protein kinases as well as in phosphotransferases of bacterial origin, our results indicate that integrity of this region is essential to enzymatic function and support the notion that it could be directly involved in ATP binding or phosphate transfer from ATP to kinase substrates.

Alternative splicing of RNAs transcribed from the chicken c-mil gene.

Two distinct c-mil-related cDNA clones have been isolated from a chicken embryo cDNA library. Results presented here show that the single chicken c-mil gene is coding for two c-mil mRNA species, different by at least 60 base pairs and generated by an alternative splicing mechanism. These mRNA molecules can be translated into two distinct proteins of 73 and 71 kilodaltons.