Genetic dissection of dome formation in a mammary cell line: identification of two genes with opposing action

Natural antisense transcripts enhance bone formation by increasing sense IFITM5 transcription

Interferon induced transmembrane protein 5 (IFITM5) has been recognized as an osteoblast differentiation factor. Its regulation, however, is still unclear. In this report, four novel naturally occurring antisense transcripts of rat IFITM2 and IFITM5 transcribed from the opposite strand of the IFITM gene locus, were isolated and characterized. They are alternatively transcribed from rat chromosome 1 and expressed at relatively high levels during early differentiation of primary isolates of rat osteoblast cells. There are two common fragments in all of the isoform cDNA sequences that are complimentary to both IFITM2 and IFITM5 respectively. There is an additional unique region in one isoform, immediately downstream of the putative IFITM5 complimentary region, which is also complimentary to IFITM cDNA sequence. Reading frame analysis showed that these antisense transcripts are non protein coding mRNAs. We investigated the expression of these antisense transcripts and their effects on IFITM expression as well as osteoblast differentiation. All isoforms were positively correlated with IFITM5 expression and antisense specific siRNAs inhibited osteoblast differentiation significantly. In contrast, these antisense transcripts had no effect on the expression of IFITM2. We speculate that IFITM5 may be regulated by antisense transcripts.

Shear stress reverses dome formation in confluent renal tubular cells

BACKGROUND/AIMS

It has been shown that MDCK cells, a cell line derived from canine renal tubules, develop cell domes due to fluid pumped under cell monolayer and focal detachment from the adhesion surface. In vitro studies have shown that primary cilia of kidney tubular epithelial cells act as mechanosensors, increasing intracellular calcium within seconds upon changes in fluid shear stress (SS) on cell membrane. We then studied the effect of prolonged SS exposure on cell dome formation in confluent MDCK cell monolayers.

METHODS

A parallel plate flow chamber was used to apply laminar SS at 2 dynes/cm(2) to confluent cell monolayers for 6 hours. Control MDCK cell monolayers were maintained in static condition. The effects of Ca(2+) blockade and cell deciliation on SS exposure were also investigated.

RESULTS

Seven days after reaching confluence, static cultures developed liquid filled domes, elevating from culture plate. Exposure to SS induced almost complete disappearance of cell domes (0.4±0.8 vs. 11.4±2.8 domes/mm(2), p < 0.01, n=14). SS induced dome disappearance took place within minutes to hours, as shown by time-lapse videomicroscopy. Exposure to SS importantly affected cell cytoskeleton altering actin stress fibers expression and organization, and the distribution of tight junction protein ZO-1. Dome disappearance induced by flow was completely prevented in the presence of EGTA or after cell deciliation.

CONCLUSIONS

These data indicate that kidney tubular cells are sensitive to apical flow and that these effects are mediated by primary cilia by regulation of Ca(2+) entry in to the cell. SS induced Ca(2+) entry provokes contraction of cortical actin ring that tenses cell-cell borders and decreases basal stress fibers. These processes may increase paracellular permeability and decrease basal adhesion making dome disappear. Elucidation of the effects of apical fluid flow on tubular cell function may open new insights on the pathophysiology of kidney diseases associated with cilia dysfunction.

Characterization of the osteoblast-specific transmembrane protein IFITM5 and analysis of IFITM5-deficient mice

Interferon-inducible transmembrane protein 5 (IFITM5) is an osteoblast-specific membrane protein whose expression peaks around the early mineralization stage during the osteoblast maturation process. To investigate IFITM5 function, we first sought to identify which proteins interact with IFITM5. Liquid chromatography mass spectrometry revealed that FK506-binding protein 11 (FKBP11) co-immunoprecipitated with IFITM5. FKBP11 is the only protein it was found to interact with in osteoblasts, while IFITM5 interacts with several proteins in fibroblasts. FKBPs are involved in protein folding and immunosuppressant binding, but we could not be sure that IFITM5 participated in these activities when bound to FKBP11. Thus, we generated Ifitm5-deficient mice and analyzed their skeletal phenotypes. The skeletons, especially the long bones, of homozygous mutants (Ifitm5(-/-)) were smaller than those of heterozygous mutants (Ifitm5(+/-)), although we did not observe any significant differences in bone morphometric parameters. The effect of Ifitm5 deficiency on bone formation was more significant in newborns than in young and adult mice, suggesting that Ifitm5 deficiency might have a greater effect on prenatal bone development. Overall, the effect of Ifitm5 deficiency on bone formation was less than we expected. We hypothesize that this may have resulted from a compensatory mechanism in Ifitm5-deficient mice.

Distinct populations of tumor-initiating cells derived from a tumor generated by rat mammary cancer stem cells

Tumors derived from rat LA7 cancer stem cells (CSCs) contain a hierarchy of cells with different capacities to generate self-renewing spheres and tubules serially ex vivo and to evoke tumors in vivo. We isolated two morphologically distinct cell types with distinct tumorigenic potential from LA7-evoked tumors: cells with polygonal morphology that are characterized by expression of p21/(WAF1) and p63 and display hallmarks of CSCs and elongated epithelial cells, which generate tumors with far less heterogeneity than LA7 CSCs. Serial transplantation of elongated epithelial cells results in progressive loss of tumorigenic potential; tumor heterogeneity; CD44, E-cadherin, and epithelial cytokeratin expression and increased alpha-smooth muscle actin I and vimentin expression. In contrast, serial transplantation of LA7 CSCs can be performed indefinitely and results in tumors that maintain their heterogeneity, consistent with self-renewal and multilineage differentiation potential. Collectively, our data show that polygonal cells are CSCs, whereas epithelial elongated cells are lineage-committed progenitors with tumorigenic potential, and suggest that tumor progenitors, although lacking indefinite self-renewal potential, nevertheless may make a substantial contribution to tumor development. Because LA7 cells can switch between conditions that favor maintenance of pure CSCs vs. differentiation into other tumor cell types, this cell system provides the opportunity to study factors that influence CSC self-renewal and differentiation. One factor, p63, was identified as a key gene regulating the transition between CSCs and early progenitor cells.

The regulation of selective and nonselective Na+ conductances in H441 human airway epithelial cells

Analysis of membrane currents recorded from hormone-deprived H441 cells showed that the membrane potential (V(m)) in single cells (approximately -80 mV) was unaffected by lowering [Na+]o or [Cl(-)]o, indicating that cellular Na+ and Cl(-) conductances (GNa and GCl, respectively) are negligible. Although insulin (20 nM, approximately 24 h) and dexamethasone (0.2 microM, approximately 24 h) both depolarized Vm by approximately 20 mV, the response to insulin reflected a rise in GCl mediated via phosphatidylinositol 3-kinase (PI3K) whereas dexamethasone acted by inducing a serum- and glucocorticoid-regulated kinase 1 (SGK1)-dependent rise in GNa. Although insulin stimulation/PI3K-P110 alpha expression did not directly increase GNa, these maneuvers augmented the dexamethasone-induced conductance. The glucocorticoid/SGK1-induced GNa in single cells discriminated poorly between Na+ and K+ (PNa/PK approximately 0.6), was insensitive to amiloride (1 mM), but was partially blocked by LaCl3 (La3+; 1 mM, approximately 80%), pimozide (0.1 mM, approximately 40%), and dichlorobenzamil (15 microM, approximately 15%). Cells growing as small groups, on the other hand, expressed an amiloride-sensitive (10 microM), selective GNa that displayed the same pattern of hormonal regulation as the nonselective conductance in single cells. These data therefore 1) confirm that H441 cells can express selective or nonselective GNa (14, 48), 2) show that these conductances are both induced by glucocorticoids/SGK1 and subject to PI3K-dependent regulation, and 3) establish that cell-cell contact is vitally important to the development of Na+ selectivity and amiloride sensitivity.

Restriction of sulfur-containing amino acids alters claudin composition and improves tight junction barrier function

Restriction of sulfur-containing amino acids (SCAA) has been shown to elicit a similar increase in life span and decrease in age-related morbidity as caloric restriction. The singular importance of epithelial barrier function in both physiological homeostasis and prevention of inflammation raised the issue of examining the effect of SCAA restriction on epithelial tight junction structure and permeability. Using a well-described in vitro, epithelial model, the LLC-PK(1) renal epithelial cell line, we studied the effects of SCAA restriction in culture medium. Reduction of methionine by 90%, cysteine by 50%, and total elimination of cystine resulted in dramatically lower intracellular pools of these amino acids and their metabolite, taurine, but the intracellular pools of the non-SCAA were all elevated. Cell growth and differentiation were maintained, and both confluent cell density and transepithelial short circuit current were unaffected. Certain tight junctional proteins, such as occludin and claudins-1 and -2 were not altered. However, claudins-3 and -7 were significantly decreased in abundance, whereas claudins-4 and -5 were markedly increased in abundance. The functional result of these structural changes was improved barrier function, as evidenced by increased transepithelial electrical resistance and decreased transepithelial (paracellular) diffusion of D-mannitol.

The properties of a mammary gland cancer stem cell

The cancer stem cell hypothesis posits that tumors are derived from a single cancer-initiating cell with stem cell properties. The task of identifying and characterizing a single cancer-initiating cell with stem cell properties has proven technically difficult because of the scarcity of the cancer stem cells in the tissue of origin and the lack of specific markers for cancer stem cells. Here we show that a single LA7 cell derived from rat mammary adenocarcinoma has the following properties: the differentiation potential to generate all of the cell lineages of the mammary gland; the ability to generate branched duct-like structures that recapitulate morphologically and functionally the ductal-alveolar-like architecture of the mammary tree; and the capacity to initiate heterogeneous tumors in nonobese diabetic-SCID mice. In addition, we show that cultured cells derived from tumors generated by a single LA7 cell-injection have properties similar to LA7 cells, can generate all of the cell lineages of the mammary gland, and recapitulate the ductal-alveolar-like architecture of the mammary tree. The properties of self-renewal, extensive capacity for proliferation, multilineage differentiation potential, and single-cell tumor-initiation potential suggest that LA7 cells are cancer stem cells and can be used as a model system to study the dynamics of tumor formation at the single-cell level.

Cell confluence-induced activation of signal transducer and activator of transcription-3 (Stat3) triggers epithelial dome formation via augmentation of sodium hydrogen exchanger-3 (NHE3) expression

Cell confluence induces the activation of signal transducer and activator of transcription-3 (Stat3) in various cancer and epithelial cells, yet the biological implications and the associated regulatory mechanisms remain unclear. Because confluent polarized epithelia demonstrate dome formation and sodium influx that mimic the onset of differentiation, we sought to elucidate the role of Stat3 in association with the regulation of selective epithelial transporters in this biological phenomenon. This study established the correlation between Stat3 activation and cell confluence-induced dome formation in Madin-Darby canine kidney cells (MDCK) by following Stat3 activation events in dome-forming cells. Epifluorescent and confocal microscopy provided evidence showing specific localization of phosphorylated Stat3 Tyr(705) in the nuclei of dome-forming cells at initial stages. The relationship was further elucidated by the establishment of tetracycline-inducible expression of constitutive Stat3 mutant (Stat3-C) in MDCK cells or expression of dominant negative Stat3 (Stat3-D) stable cell lines (MDCK and NMuMG). Dome formation was promoted by the expression of Stat3-C but inhibited by Stat3-D. Two trans-epithelial transporters, NHE3 and ENaC alpha-subunit, were found to be increased during cell confluence. Interestingly, NHE3 expression could be specifically up-regulated by Stat3-C but inhibited by Stat3-D through promoter regulation, whereas NHE1 and ENaC alpha-subunit were not affected by Stat3 expression. Application of NHE3 shRNA, NHE3 inhibitors (EIPA and S3226) suppressed confluence-induced dome formation in MDCK or NMuMG cells. These results demonstrate a cell confluence-induced Stat3 signaling pathway in epithelial cells in triggering dome formation through NHE3 augmentation.

TBX3, the gene mutated in ulnar-mammary syndrome, promotes growth of mammary epithelial cells via repression of p19ARF, independently of p53

TBX3, the gene mutated in ulnar-mammary syndrome (UMS), is involved in the production of a transcription factor of the T-box family, known to inhibit transcription from the p14ARF (p19ARF in mouse) promoter in fibroblasts and to contribute to cell immortalization. One of the main features of the UMS phenotype is the severe hypoplasia of the breast, associated with haploinsufficiency of the TBX3 gene product. In mice homozygous for the targeted disruption of Tbx3, the mammary glands (MGs) are nearly absent from early stages of embryogenesis, whereas in heterozygous adults, the MGs show reduced ductal branching. All these data strongly suggest a specific role of TBX3 in promoting the growth of mammary epithelial cells (MECs), although direct evidence of this is lacking. Here, we provide data showing the growth-promoting function of Tbx3 in several models of MECs, in association with its ability to repress the ARF promoter. However, no effect of Tbx3 on cell differentiation or apoptosis has been observed. The growth promoting function also entails the down-regulation of p21 ( CIP1/WAF ) and an increase in cyclin D1 but is independent of p53 and Mdm2 cell-cycle regulatory proteins, as p53-null MECs show similar growth responses associated with the up- or down-regulation of Tbx3. This is the first direct evidence that the level of Tbx3 expression positively controls the proliferation of MECs via pathways alternative to Mdm2-p53.

Profiling of genes differentially expressed in a rat of early and later gestational ages with high-density oligonucleotide DNA array

The early gestational fetus heals dermal wounds rapidly and scarlessly. This phenomenon appears to be intrinsic to fetal skin and is probably modulated by interplay of many genes. We ventured to study differences in gene expression between earlier gestational skin (EGS) and later gestational skin (LGS) with the aid of high-density oligonucleotide DNA array to explore the molecular mechanism underlying scarless healing. Total RNA was isolated from fetal Wistar rat skin of the scarless (E15) and scar-forming (E18) periods of gestation (term=21.5 days), and purified to mRNAs. Both the mRNAs from EGS and LGS were reversely transcribed to cDNAs, and were labeled with the incorporation of fluorescent dCTP for preparing the hybridization probes through single primer amplification reaction and Klenow labeling methods. The mixed probes were then hybridized to the oligonucleotide DNA arrays that contained 5,705 DNA fragments representing 5,705 rat genes. After highly stringent washing, the microarray was scanned for fluorescent signals to display the differentially expressed genes between two groups of tissues. Among 5,705 rat genes, there were 53 genes (0.93%) with differentially expressed levels between EGS and LGS; 27 genes, including fibroblast growth factor 8 and follistatin, were up-regulated (0.47%); and 26 genes, containing lymphoid enhancer binding factor-1 and beta-catenin, were down-regulated (0.46%) in fetal skin of scarless period vs. scar-forming period. Analyses of genes related to ion channels, growth factors, extracellular matrix and cellular skeleton, and movement confirmed that our molecular data obtained by oligonucleotide DNA array were consistent with the published biochemical and clinical findings of fetal scarless healing. Stronger expression of fibroblast growth factor 8, follistatin, and weaker expression of lymphoid enhancer binding factor-1 and beta-catenin in EGS vs. LGS were also testified with reverse transcription-polymerase chain reaction and Western blotting methods. Oligonucleotide DNA array was a powerful tool for investigating different gene expression between scarless and scar-forming periods of gestation in the rat fetal skin. Many genes were involved in the phenotypic transition from scarless to scar-forming wound repair during gestation. Further analysis of the obtained genes will help to understand the molecular mechanism of fetal scarless healing.

Claudins--key pieces in the tight junction puzzle

Tight junctions restrict the flow of ions and aqueous molecules between cells by forming a selective barrier to the paracellular pathway. Permeability of the tight junction barrier is determined by a class of transmembrane proteins known as claudins. The relationship between claudins and paracellular permeability is complex and determined not only by the profile of claudin expression but also by the arrangement of claudins and other proteins into tight junction strands. This review summarizes progress in understanding how claudins are assembled into tight junctions and how they interact with other tight junction proteins.

Expression of the mouse fragilis gene products in immune cells and association with receptor signaling complexes

The mouse genome possesses five genes encoding proteins homologous to human Leu-13. The Leu-13 protein associates with immune cell receptor activation complexes: a monoclonal antibody against Leu-13 induces T and B cells to form homotypic aggregates, inhibits activation-induced proliferation and induces the shedding of L-selectin. The mouse fragilis proteins have not been previously analyzed as components of the immune response. Antibody and nucleic acid reagents were generated that are specific for each of the five fragilis gene products. Expression of some of these genes (fragilis and fragilis3) is wide spread in a variety of mouse immune (and nonimmune) tissues while others (fragilis5) appear to be much more restricted. These proteins have been predicted to span the membrane twice with both amino- and carboxyl-terminal sequences extracellular: we show that a highly conserved loop of the protein between the transmembrane domains is intracellular. The fragilis proteins are associated with tetraspanin proteins CD81 and CD9: B cell activation positions fragilis into lipid rafts along with the CD81, CD19, and CD21. The mouse functional equivalent to human Leu-13 may not be single gene product, but instead may require the contribution of multiple fragilis proteins.

Inducible expression of Snail selectively increases paracellular ion permeability and differentially modulates tight junction proteins

Constitutive expression of the transcription factor Snail was previously shown to trigger complete epithelial-mesenchymal transition (EMT). The aim of this study was to determine whether inducible expression of Snail could modify epithelial properties without eliciting full mesenchymal conversion. For this purpose, we expressed mouse Snail (mSnail) cDNA in Madin-Darby canine kidney (MDCK) cells under the control of a doxycycline-repressible transactivator. Inducible expression of Snail did not result in overt EMT but induced a number of phenotypic alterations of MDCK cells, the most significant of which was the absence of fluid-filled blisterlike structures called “domes.” To understand the mechanisms responsible for dome suppression, we assessed the effect of mSnail expression on epithelial barrier function. Although mSnail did not alter tight junction (TJ) organization and permeability to uncharged solutes, it markedly decreased transepithelial electrical resistance. In light of these findings, we evaluated the ability of MDCK cell monolayers to maintain ionic gradients and found that expression of mSnail selectively increases Na+and Cl−permeability. Analysis of the expression of claudins, transmembrane proteins that regulate TJ ionic permeability, showed that mSnail induces a moderate decrease in claudin-2 and a substantial decrease in claudin-4 and -7 expression. Together, these results suggest that induction of mSnail selectively increases the ionic permeability of TJs by differentially modulating the expression of specific claudins.

Altered expression of CLC, DSG3, EMP3, S100A2, and SLPI in corneal epithelium from keratoconus patients

PURPOSE

This investigation was designed to determine whether the five genes, CLC, DSG3, EMP3, S100A2 and SLPI, are differentially expressed in keratoconus, as indicated from another study.

METHODS

Gene expression was monitored using quantitative real-time PCR on 14 keratoconus samples and 16 controls, and normalized to GAPDH and B2M. The DSG3, S100A2, and SLPI proteins were quantified by Western blotting, and the cellular localization was determined by immunohistochemistry. One of the genes, CLC, was reduced in gene expression and its four exons were sequenced.

RESULTS

The five genes were all differentially expressed in keratoconus (P < 0.04) and so were at least three of the encoded proteins (P = 0.009). DSG3 was expressed in association with the cell membrane of the basal and suprabasal epithelial cells, and S100A2 was expressed in the nucleus and cytoplasm, often as intracellular granules. Two SNPs (rs374185 and rs384138) were observed in the CLC gene, each with an allele frequency of 68%. No other mutations were detected.

CONCLUSIONS

The five genes, and three of the encoded proteins, were shown differentially expressed between a group of keratoconus patients and a reference group using different techniques. These alterations, in combination with earlier findings, strongly demonstrate the genes to be involved in the corneal disease. We suggest the unambiguously expressed DSG3 protein to be used as a marker for keratoconus.

Differentiation of epithelial Na+ channel function. An in vitro model

Confluent monolayers of epithelial cells grown on nonporous support form fluid-filled hemicysts called domes, which reflect active ion transport across the epithelium. Clara-like H441 lung adenocarcinoma cells grown on glass supports and exposed to 50 nM dexamethasone developed domes in a time-dependent fashion. Uplifting of small groups of cells occurred within 6-12 h, well formed domes appeared between 24 and 48 h, and after 7 days, individual domes started to merge. Cells inside of domes compared with those outside domes, or with monolayers not exposed to dexamethasone, differed by higher surfactant production, an increased cytokeratin expression, and the localization of claudin-4 proteins to the plasma membrane. In patch clamp studies, amiloride-blockable sodium currents were detected exclusively in cells inside domes, whereas in cells outside of domes, sodium crossed the membrane through La3+-sensitive nonspecific cation channels. Cells grown on permeable support without dexamethasone expressed amiloride-sensitive currents only after tight electrical coupling was achieved (transepithelial electrical resistance (R(t)) > 1 kilohm). In real-time quantitative PCR experiments, the addition of dexamethasone increased the content of claudin-4, occludin, and Na+ channel gamma-subunit (gamma-ENaC) mRNAs by 1.34-, 1.32-, and 1.80-fold, respectively, after 1 h and was followed by an increase at 6 h in the content of mRNA of alpha- and beta-ENaC and of alpha1- and beta1-Na,K-ATPase. In the absence of dexamethasone, neither change in gene expression nor cell uplifting was observed. Our data suggest that during epithelial differentiation, coordinated expression of tight junction proteins precedes the development of vectorial transport of sodium, which in turn leads to the fluid accumulation in basolateral spaces that is responsible for dome formation.

Association of rat8 with Fyn protein kinase via lipid rafts is required for rat mammary cell differentiation in vitro

We previously identified rat8 in the pathway involved in epithelial cell differentiation that occurs in the rat mammary gland at pregnancy when tubules and alveoli are formed. rat8, which encodes an IFN-inducible membrane protein, is the rat homologue of the mouse gene fragilis. By differential detergent extraction and isopycnic sucrose density gradients, we show that rat8 protein is associated to lipid membrane domains together with Lyn and Fyn, members of the Src tyrosine kinase family. We also show that recruitment of rat8 to lipid membrane domains is a necessary step in mammary epithelial cell differentiation. Immunoprecipitation analysis, performed with an anti-Fyn protein antibody, shows that rat8 was present in the Fyn immunoprecipitate. Antisense oligonucleotides, used to inhibit Fyn protein expression, block mammary cell differentiation. Taken together, these results suggest that the functional interaction, via lipid membrane domains, of rat8 and Fyn proteins is required for mammary cell differentiation. Therefore, rat8, like fragilis, may be involved in developmental decisions and the demarcation of a subset of cells in the mammary gland that cause epithelial cells to develop into a network of tubuloalveolar structures involved in secretion.

Simultaneous changes in the function and expression of beta 1 integrins during the growth arrest of poorly differentiated colorectal cells (LISP-1)

Cells usually lose adhesion and increase proliferation and migration during malignant transformation. Here, we studied how proliferation can affect the other two characteristics, which ultimately lead to invasion and metastasis. We determined the expression of beta 1 integrins, as well as adhesion and migration towards laminin-1, fibronectin, collagens type I and type IV presented by LISP-1 colorectal cancer cells exposed to 2.5% dimethyl sulfoxide (DMSO), an agent capable of decreasing proliferation in this poorly differentiated colorectal cell line. Untreated cells (control), as shown by flow cytometry and monoclonal antibodies, expressed alpha 2 (63.8 11.3% positive cells), alpha 3 (93.3 7.0%), alpha 5 (50.4 12.0%) and alpha 6 (34.1 4.9%) integrins but not alpha1, alpha 4, alpha v or 4. Cells adhered well to laminin-1 (73.4 6.0%) and fibronectin (40.0 2.0%) substrates but very little to collagens. By using blocking monoclonal antibodies, we showed that alpha 2, alpha 3 and alpha 6 mediated laminin-1 adhesion, but neither alpha 3 nor alpha 5 contributed to fibronectin adherence. DMSO arrested cells at G0/G1 (control: 55.0 2.4% vs DMSO: 70.7 2.5%) while simultaneously reducing alpha 5 (24.2 19%) and alpha 6 (14.3 10.8%) expression as well as c-myc mRNA (7-fold), the latter shown by Northern blotting. Although the adhesion rate did not change after exposure to DMSO, alpha 3 and alpha 5 played a major role in laminin-1 and fibronectin adhesion, respectively. Migration towards laminin-1, which was clearly increased upon exposure to DMSO (control: 6 2 cells vs DMSO: 64 6 cells), was blocked by an antibody against alpha 6. We conclude that the effects of DMSO on LISP-1 proliferation were accompanied by concurrent changes in the expression and function of integrins, consequently modulating adhesion/migration, and revealing a complex interplay between function/expression and the proliferative state of cells.

Soluble extracts from Helicobacter pylori induce dome formation in polarized intestinal epithelial monolayers in a laminin-dependent manner

Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid "dome" formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding alpha 6 beta 4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response.

Establishment and characterization of clonal cell lines from the vagina of p53-deficient young mice

Clonal cell lines have been established from vagina of prepubertal female p53(-/-) mice. Because the mouse vagina has a dual origin (the cranial three-fifths derived from the Müllerian duct and the caudal two-fifths derived from the urogenital sinus), both parts were separately subjected to cloning. Sixteen epithelial and two fibroblastic cell lines were established from the cranial three-fifths (Müllerian vagina group), and four epithelial and three fibroblastic cell lines were established from the caudal two-fifths (sinus vagina group). They were maintained in Dulbecco's modified Eagle medium and Ham's nutrient mixture F-12 containing 10% fetal calf serum and 17 beta-estradiol at 10(-8) M. Two cell lines (one epithelial and one fibroblastic) were examined using soft agar assay, but no colonies were formed. The doubling time of the cell lines was approximately 24 h, and all of them divided more than 200 times without crisis, suggesting that they were immortalized. All epithelial cell lines expressed cytokeratin 8. However, the epithelial cell lines expressed cytokeratin 14 and cytokeratin 10 when exposed to medium containing different concentrations of Ca(2+). Fibroblastic cell lines expressed vimentin. All epithelial and fibroblastic cell lines expressed estrogen receptor-alpha protein. This is the first successful establishment of clonal cell lines from the normal mouse vagina, and these lines may provide good models in vitro of the vagina for the study of the mechanism of estrogen action.

Proteomic dissection of dome formation in a mammary cell line

The study of the development of the mammary gland at the molecular level in animals is difficult because of the complex tissue organization. This review introduces a proteomic approach to investigate mammary gland development in a cell culture system that we have previously developed as an in vitro model for studying mammary cell differentiation. The model is based on two cell lines, one of which is able to differentiate spontaneously and produce hemispherical blisters, called domes, when confluent. Through proteomic dissection of dome-forming cells, two types of key regulatory genes have been identified: genes inducing cellular structural modifications and genes related to functional modifications. We identified several genes in the pathway leading to dome formation in vitro and showed that the functional and structural changes taking place in dome-forming cells correspond to cellular changes occurring in vivo when tubules and alveoli are developed in the mammary gland at pregnancy.

Dome formation in cell cultures as expression of an early stage of lactogenic differentiation of the mammary gland

The study of the development of the mammary gland at the molecular level in the animal is difficult because of the complex tissue organization of the gland. We have previously developed an in vitro system for genetic analysis of mammary cell differentiation, based on the cell line LA7 clonally derived from a rat mammary adenocarcinoma. This cell line, after induction with DMSO, differentiates forming structures called domes. This process is under strict gene regulation, and we have previously identified several of the genes involved. In the present paper, we have defined the meaning of dome formation in relation to mammary development, by showing that treatment of LA7 cells with the lactogenic hormones hydrocortisone and prolactin induces dome formation; in the animal, these hormones precede and accompany milk production. Moreover, dome formation is accompanied by expression within the cells of the milk protein genes WDMN1 and beta-casein, which are differentiation markers for the gland during pregnancy and lactation. We also show that two proteins, highly expressed in the mammary gland during lactation, HSP90-beta and annexin I, are strongly expressed in DMSO-induced LA7 cells. Both proteins are essential in the formation of domes because when their synthesis is blocked by antisense RNA oligonucleotides, dome formation is abolished. Thus our in vitro system is a model for lobulo-alveolar development, and the genes identified in the pathway of dome formation are likely to be involved in the early differentiation steps occurring in the rat mammary gland during pregnancy and lactation.

Proteomic dissection of dome formation in a mammary cell line: role of tropomyosin-5b and maspin

In this work we extended the study of genes controlling the formation of specific differentiation structures called "domes" formed by the rat mammary adenocarcinoma cell line LA7 under the influence of DMSO. We have reported previously that an interferon-inducible gene, rat-8, and the beta-subunit of the epithelial sodium channel (ENaC) play a fundamental role in this process. Now, we used a proteomic approach to identify proteins differentially expressed either in DMSO-induced LA7 or in 106A10 cells. Two differentially expressed proteins were investigated. The first, tropomyosin-5b, strongly expressed in DMSO-induced LA7 cells, is needed for dome formation because its synthesis inhibition by the antisense RNA technology abolished domes. The second protein, maspin, strongly expressed in the uninduced 106A10 cell line, inhibits dome formation because 106A10 cells, transfected with rat8 cDNA (the function of which is required for the organization of these structures), acquired the ability to develop domes when cultured in presence of an antimaspin antibody. Dome formation in these cultures are accompanied by ENaC beta-subunit expression in the absence of DMSO. Therefore, dome formation requires the expression of tropomyosin-5b, in addition to the ENaC beta-subunit and the rat8 proteins, and is under the negative control of maspin.