Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “differentiation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36Linked to original sources
PubMed1988

Inhibition of differentiation and affinity purification with a monoclonal antibody to a myeloid cell differentiation-inducing protein.

The normal myeloid hematopoietic regulatory proteins include four growth-inducing proteins called colony-stimulating factors (CSF), including interleukin-3 (IL-3), or macrophage and granulocyte inducers, type 1 (MGI-1), and another type of protein (MGI-2) with no myeloid cell growth-inducing activity that induces differentiation of normal myeloid precursor cells and certain clones of myeloid leukemic cells. An IgG2a monoclonal antibody was prepared and it neutralized two forms of MGI-2 (MGI-2A and MGI-2B) produced by mouse Krebs ascites tumor cells. The monoclonal antibody was used for affinity purification of MGI-2. This antibody also neutralized MGI-2 produced by normal mouse macrophages, normal myeloblasts incubated with IL-3, and MGI-2 produced by the lungs and found in the serum of mice injected with lipopolysaccharide (LPS). The anti-MGI-2 antibody did not inhibit the activity of any one of the four myeloid growth-inducing proteins (CSF or IL-3 = MGI-1), IL-1, tumor necrosis factor, or lymphotoxin. This antibody also inhibited induction of differentiation of myeloid leukemic cells by LPS, which is mediated by the endogenous production of MGI-2, but did not inhibit induction of differentiation in these leukemic cells by dexamethasone or cytosine arabinoside, which is not mediated by MGI-2. Anti-MGI-2 antibody thus inhibited differentiation when MGI-2 was added externally to cells or when it was mediated by endogenously produced MGI-2.

Animals↗
PubMed1988

Differentiation-induced gene expression in 3T3-L1 preadipocytes. Characterization of a differentially expressed gene encoding stearoyl-CoA desaturase.

Previous studies have shown that differentiation of 3T3-L1 preadipocytes leads to the activation of transcription of an unidentified gene which encodes a 4.9-kilobase (kb) mRNA. Several cDNAs that include the complete sequence of this mRNA were obtained and used to isolate and characterize the gene. Analysis of the nucleotide and amino acid sequences of both cDNA and genomic clones revealed that the gene encodes the mouse stearoyl-CoA desaturase (SCD), an enzyme known to be expressed upon differentiation of 3T3-L1 preadipocytes. The predicted amino acid sequence (355 residues) of the mouse 3T3-L1 adipocyte SCD exhibits 92% identity to that of the rat liver SCD. There is also a high degree of nucleotide sequence identity between the mouse and rat mRNAs in their unusually long approximately 3.5-kb 3'-untranslated regions. Mice fed a diet containing unsaturated triacylglycerides express SCD mRNA only in adipose tissue, whereas mice starved and refed a fat-free diet, express SCD mRNA in both liver and adipose tissue. The mouse gene for the desaturase spans approximately 15 kb and contains 6 exons and 5 introns with all intron-exon junctions conforming to the GT/AG splicing rule. As determined by S1 nuclease mapping and primer extension analysis, the transcriptional initiation site maps 152 nucleotides upstream from the initiation methionine codon. A canonical promoter "TATA" box is located 30 base pairs upstream of the Cap site. A typical "CCAAT" box sequence is not present in the adjacent 5'-flanking region; however, there is a GC-rich sequence (at nucleotide -215) similar to the binding site for the nuclear transcription factor Sp1. Upstream from the transcriptional initiation site are elements with homology (approximately 75%) to the putative fat-specific transcriptional element FSE2 and core consensus sequences for cAMP and glucocorticoid regulatory elements. A chimeric construct, containing 363 base pairs of 5'-flanking sequence and 30 nucleotides of 5'-untranslated sequence of the mouse SCD gene ligated to the bacterial chloramphenicol acetyltransferase gene, was transfected into 3T3-L1 cells. When cells were induced to differentiate into adipocytes, expression of the SCD chloramphenicol acetyltransferase gene increased approximately 63-fold, suggesting that the SCD promoter region contains elements that mediate the response to adipogenic agents which induce differentiation.

Adipose Tissue↗
PubMed1987

Suppressor T cell growth and differentiation: production of suppressor T cell differentiation factor by the murine thymoma BW5147.

Previous studies have identified a lymphokine, termed Ts differentiation factor (TsDF), in primary MLR supernatants that induces effector function of alloantigen-primed MLR-Ts. The present report describes constitutive production of TsDF by the murine thymoma BW5147, and its use to analyze alloantigen and TsDF requirements for MLR-Ts activation to TsF production. Serum-free supernatants of BW5147 restored the capacity of MLR-TsF production to alloantigen-primed MLR-Ts cultured with glutaraldehyde-fixed allogeneic stimulator cells, and were not themselves directly suppressive in the MLR assay. BW5147 supernatant induced MLR-TsF production from primed L3T4-Ly2+ MLR-Ts in the absence of concomitant proliferation, suggesting that the function of BW5147 supernatant, like that of MLR-derived TsDF, is a differentiative rather than a proliferative one, and is required for the synthesis or release of TsF. The differentiative activity of BW5147 supernatant was associated with a molecular species of approximately 14,500 m.w. by HPLC fractionation and was expressed independently of detectable IL 2, IL 3, IFN-gamma, and IL 1. The functional activity of BW5147 supernatant has therefore been provisionally designated BW5147-derived Ts differentiative factor, or BW-TsDF. By using BW-TsDF, it was demonstrated that MLR-Ts fail to respond to TsDF in the absence of, or preceding, reexposure to priming alloantigen. Instead, alloantigen binding by primed MLR-Ts appears to create a transient state of TsDF responsiveness. Primed MLR-Ts were fully sensitive to delayed addition of TsDF for approximately 12 hr after reexposure to alloantigen, but became TsDF-unresponsive within 24 to 36 hr. MLR-Ts cultured alone for 36 hr were fully responsive to the combined addition of TsDF and alloantigen. Thus, MLR-Ts activation to TsF release requires the sequential events of specific alloantigen binding, which induces a TsDF-responsive state, followed by interaction with TsDF. The transience of induced TsDF responsiveness suggests a precise mechanism for control of antigen-initiated Ts activation to effector function.

Animals↗
PubMed1987

Regulation of B cell maturation and differentiation. I. Suppression of pokeweed mitogen-induced B cell differentiation by tumor necrosis factor (TNF).

Growth and differentiation of B cells into Ig-secreting plasma cells is regulated by both T cells and macrophages and/or their secreted factors. Although the regulatory role of various cell-derived factors has been examined, the involvement of the macrophage-derived factor, TNF, in human B cell growth and differentiation has not yet been investigated. In the present study we examine the role of rTNF in polyclonal B cell response of human PBL induced by PWM. The addition of rTNF at the initiation of the culture resulted in the dose-dependent inhibition of the generation of both IgG and IgM PFC. Inhibition of PFC development followed the same dose response as rTNF-mediated cytotoxicity against a TNF-sensitive tumor target. The mechanism of rTNF-mediated suppression was examined in different experimental systems. Recombinant TNF did not affect the viability or proliferation of either the T cell or B cell subpopulations, suggesting that TNF does not mediate its suppressive effect by cytotoxic mechanisms. Kinetic studies in which rTNF was added at different times after initiation of culture indicated that inhibition can be observed as late as 4 days of culture and suggested that TNF acts at a late phase of the growth and differentiation pathway of B cells. In further studies we examined the cellular level of TNF-mediated suppression. The addition of rTNF to supernatants containing helper factors and enriched B cells resulted in no inhibition, suggesting that TNF does not act at the B cell level. This was confirmed by demonstrating that rTNF does not inhibit spontaneous PFC development by the CESS B cell line. The effect of TNF on T cell subpopulations was examined by using normal or irradiated T cells, which inactivate suppressor cells. Addition of rTNF to B cells combined with either T cell population suppressed both IgG and IgM PFC development, indicating that the target cell for suppression is the T helper cell but not ruling out an effect on macrophages or the T suppressor cells. Combined, the observed results demonstrate that rTNF suppresses PWM-induced B cell differentiation without affecting B cell proliferation. TNF appears to mediate the suppression by acting directly on T helper cells or else by regulating the production of factors controlling T cell activation and lymphokine secretion.

Antibody Formation↗
PubMed1986

Variants of a human monocytic leukemia cell line (THP-1): induction of differentiation by retinoic acid, interferon-gamma, and T-lymphocyte-derived differentiation-inducing activity.

Induction of terminal differentiation of two variant sublines derived from the human monocytic leukemia cell line THP-1 by all-trans-beta-retinoic acid (RA) was studied. One of the variants was approximately 10 times more resistant to RA and the other, approximately 10 times more sensitive than the parent THP-1. Differentiation of the RA-resistant variant could be induced by immune interferon (IFN-gamma) and a T-lymphocyte-derived lymphokine of a differentiation-inducing activity (DIA), alone or in combination with 10 nM RA. These induced cells showed many of functional monocyte and/or macrophage characteristics, such as superoxide anion production, phagocytosis, and antibody-dependent cellular cytotoxicity. RA suppressed the expression of Fc receptors, phagocytosis, and 5'-nucleotidase activity of the resistant cells, although not the expression of the sensitive variant. These results indicate that RA-resistant cells can be fully induced to differentiate by the combination of RA and IFN-gamma or DIA.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1986

Transforming growth factor-beta. A very potent inhibitor of myoblast differentiation, identical to the differentiation inhibitor secreted by Buffalo rat liver cells.

Transforming growth factor-beta (TGF-beta) is now known to have a number of actions in addition to the induction of phenotypic transformation in fibroblastic cells. In this paper, we characterize its inhibition of differentiation in rat myoblasts of Yaffe's L6 strain and demonstrate its identity or very close similarity to the differentiation inhibitor (DI) secreted by Buffalo rat liver cells cultured in serum-free medium. At concentrations as low as 60 pg/ml, TGF-beta gave detectable inhibition of differentiation measured as myoblast fusion and creatine kinase elevation; maximal inhibition was observed at and above 0.5 ng/ml (20 pM). The inhibition persisted as long as fresh TGF-beta was added at 48-h intervals, but it was reversed upon removal of the factor. By itself or in the presence of mitogens, TGF-beta had no mitogenic activity in the L6 cells. Concentration dependencies of human TGF-beta and the rat DI were closely parallel in three assays: inhibition of myoblast differentiation, stimulation of normal rat kidney cell growth in soft agar, and competition for displacement of labeled TGF-beta from binding sites on A549 human lung carcinoma cells. We conclude that most if not all of the DI activity found in medium conditioned by Buffalo rat liver cells can be attributed to the presence of TGF-beta or a very similar molecule. These observations also offer a potentially useful approach to study the control of myogenesis; the process(es) can be blocked in cloned L6 myoblasts by incubation with very small quantities of a pure protein in fully defined serum-free medium.

Animals↗
PubMed1984

Chemically induced differentiation of murine embryonal carcinoma in vivo: transplantation of differentiated tumors.

Murine embryonal carcinoma tumors were induced to differentiate in vivo by administration of retinoic acid. Six long-term surviving animals had seven slowly growing tumors which were transplanted s.c. into strain 129 mice. Untreated embryonal carcinomas were transplanted as controls. All of the 16 control transplants grew rapidly and killed their hosts within 25 days. All of the 24 transplants of retinoic acid-differentiated tumor survived. Sixteen experimental transplants originating from five original tumors showed no or slow growth for up to 16 weeks and were found to be histologically benign cystic teratomas. Two original tumors gave rise to eight relatively rapidly growing transplants. One tumor resulted in four histologically similar solid tumors which resembled chondrosarcomas, and the second tumor gave rise to four histologically similar solid tumors which proved to be a mixture of glioma and chondrosarcoma. Examination of the tumor sources of these latter transplants showed benign cystic teratomas with focal solid, mitotically active cellular areas which were histologically similar to the transplants. These data confirm that retinoic acid-induced differentiation of murine embryonal carcinoma cells results in altered biological potential of these cells and usually the formation of a benign teratoma. Rarely (about 1 per 2 X 10(8], the resulting differentiated cells will give rise to rapidly growing, histologically malignant tumors. One can predict such biological propensity when solid, mitotically active areas in the original tumor are found.

Animals↗
PubMed1994

Self-renewal and differentiation of stem cells in a biopotential murine leukemia: an in vitro model for differentiation therapy.

PGM-2 is a variant of the transplantable PGM-1 leukemia of strain C3H/HeJ. Freshly explanted cells had lymphoid morphology with a CD5+ CD45R (B220)- IgM- phenotype. They were not viable in unstimulated cultures, but formed IgM+ lymphoid colonies in response to interleukin-2 (IL-2), IL-4, IL-5, IL-6, IL-7, and Steel factor, and macrophage colonies in response to IL-3. IL-3-stimulated colonies had no recloning potential, but colonies from IL-7 cultures gave rise to large numbers of secondary macrophage colonies in IL-3-stimulated cultures and secondary lymphoid colonies in IL-7-stimulated cultures. The latter ones could be serially transferred in vitro for several months, and formed typical PGM-2 tumors in vivo. IL-7-stimulated colonies could therefore be used to measure leukemic stem cells in vitro. Supramaximal IL-3 stimulation (2,500 U/mL) of suspension cultures was followed by an increase in overall cell numbers and a disappearance of leukemic stem cells, compatible with differentiation induction. This could not be counteracted by simultaneous stimulation with IL-7. However, lower IL-3 concentrations (500 U/mL) induced an expansion of the stem cell pool, possibly by facilitating density-dependent autostimulatory mechanisms involving endogenous production of IL-7. The system described is a simple in vitro model for differentiation therapy. It shows that leukemic stem cells can be induced by hematopoietic growth factors to undergo terminal differentiation, but the concentrations required for differentiation induction in stem cells are much higher than those required for other biologic effects. Submaximal stimulation may favor expansion rather than repression of the leukemic cell population.

Animals↗
PubMed1995

Differential effects of N-(4-hydroxyphenyl)retinamide and retinoic acid on neuroblastoma cells: apoptosis versus differentiation.

Retinoids exert various important biological effects in the control of normal growth, differentiation, and fetal development. While retinoic acid (RA) has entered clinical trials as a differentiation-promoting agent, it is only recently that the synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) has been shown to be of potential clinical interest in cancer chemoprevention and treatment. Since thus far no data exist on the effects of HPR on neural crest cell-derived tumors, we have examined its in vitro effects on neuroblastoma (NB) cell lines and found that at relevant pharmacological concentrations it induces a dose-dependent growth inhibition. The antiproliferative effects of HPR were, in six of six cell lines tested, drastically more potent that those induced by an equimolar dose of RA. Time course growth analysis showed that HPR at 3 x 10(-6) M induces a very rapid (24-72 h) fall in thymidine uptake (> 90%), whereas at 3 x 10(-7) M it exhibits cytostatic effects. In contrast to RA, HPR did not show morphological changes typical of NB cell maturation nor did it induce the expression of any cytoskeletal protein associated with neuronal differentiation. DNA flow cytofluorimetric analysis revealed that HPR did not induce an arrest in a specific phase of the cell cycle while triggering apoptosis. This phenomenon was evidenced both by the visualization of "DNA ladders" on gel electrophoresis and by a quantitative assay for evaluating programmed cell death based upon the labeling of DNA breaks with tritiated thymidine. With the latter method, apoptotic cells were detectable as early as 3-6 h after treatment of NB cells with 10(-5) M HPR, while more than 50% of cells were apoptotic by 24-72 h following exposure to 3 x 10(-6) M HPR. In contrast, RA induced a low rate of apoptosis in NB cells only after 3-5 days. Time lapse photomicroscopy showed that NB cells treated with HPR underwent a death process highly reminiscent of apoptosis, with progressive condensation of the cytoplasm around the nucleus and intense cell shrinkage. The cells then rounded up and detached from the plate. Furthermore, propidium iodide staining of the DNA showed that a high proportion of cells treated with HPR displayed a small and brightly staining nucleus; chromatin appeared aggregated into dense masses in the nuclear periphery, a typical feature of apoptotic cells. In conclusion, our study demonstrates that contrary to the differentiation-promoting activity of RA, HPR dramatically suppresses NB cell growth by inducing programmed cell death.(ABSTRACT TRUNCATED AT 400 WORDS)

Apoptosis↗
PubMed1994

Expression of the catalytic and regulatory subunits of protein phosphatase type 2A may be differentially modulated during retinoic acid-induced granulocytic differentiation of HL-60 cells.

To elucidate the regulation of protein phosphatases types 1 (PP1) and 2A (PP2A) during all-trans retinoic acid (ATRA)-induced granulocytic differentiation of HL-60 cells, the phosphatase activity, proteins, and gene expressions of PP1 and PP2A were examined. Treatment with 1 microM ATRA caused an 85% decrease in the PP2A activity in extracts from HL-60 cells, while the PP1 activity was constant. This reduction in PP2A activity appeared to parallel phenotypic and functional changes of HL-60 cells induced by ATRA. Western blot analysis showed that the level of PP2A catalytic subunit (PP2A-C) decreased during the course of ATRA-induced differentiation, whereas expressions of A and B (M(r) 55,000) regulatory subunits of PP2A were relatively unaltered. Expressions of PP1 catalytic subunit isozymes (PP1 alpha, PP1 gamma, and PP1 delta) were not significantly affected by ATRA treatment. Northern blot analysis revealed that mRNA levels of PP2A-C beta and A alpha regulatory subunits were decreased following treatment with ATRA, while levels of PP2A-C alpha and B (M(r) 55,000) alpha regulatory subunit transcripts were relatively constant. Selective down regulation of PP2A-C beta preceded the granulocytic maturation induced by ATRA. Expressions of PP2A-C isoforms and A and B regulatory subunits may be differentially modulated during ATRA-induced granulocytic differentiation of HL-60 cells.

Blotting, Northern↗
PubMed1993

Induction of monocytic differentiation and tumorigenicity by v-Ha-ras in differentiation arrested hematopoietic cells.

Activated ras genes are often associated with human myeloid leukemias with a monocytic differentiated phenotype. To investigate the role of the activated ras gene in leukemogenesis, a myeloid nontumorigenic cell line (FDC-P1) was infected with a selectable retroviral vector carrying the v-Ha-ras gene (H1neo). Infected FDC-P1 cells were not only tumorigenic, but also showed increased monocytic differentiation in vitro. Monocytic differentiation and tumorigenicity in vivo were correlated with several-fold increased levels of activated ras gene expression. Tumorigenic cells were arrested with respect to monocytic marker expression at a much later stage of macrophage differentiation than the parental noninfected FDC-P1 cells. These data thus suggest a model of how activated ras genes could be involved in the preferential induction of hematopoietic malignancies with a myelomonocytic phenotype.

Animals↗
PubMed1995

Subtraction hybridization identifies a novel melanoma differentiation associated gene, mda-7, modulated during human melanoma differentiation, growth and progression.

Cultured human melanoma cells lose proliferative capacity and terminally differentiate after treatment with the combination of recombinant human fibroblast interferon (IFN-beta) and mezerein (MEZ). Subtraction hybridization of cDNA libraries prepared from actively proliferating human H0-1 melanoma cells from cDNA libraries produced from H0-1 cells treated with IFN-beta + MEZ identifies a novel melanoma differentiation-associated (mda) cDNA, mda-7, that displays elevated expression in differentiation inducer-treated H0-1 cells. mda-7 encodes a novel protein of 206 amino acids with a predicted size of 23.8 kDa. The level of mda-7 mRNA is elevated in actively proliferating normal human melanocytes versus primary and metastatic human melanomas. In the Matrigel-assisted melanoma progression model, mda-7 expression decreases in early vertical growth phase primary human melanoma cells selected for autonomous or enhanced tumor formation in nude mice. Treatment of human melanomas with IFN-beta + MEZ, and to a lesser extent with MEZ, results in growth suppression and induced or enhanced mda-7 expression. Immunoprecipitation analyses using peptide-derived rabbit polyclonal antibodies detect increases in mda-7 protein, and a higher molecular weight protein of approximately 90 to 100 kDa, in MEZ and IFN-beta + MEZ treated H0-1 cells. mda-7 is a highly conserved gene with an homologous sequence in the genome of yeast. Transfection of mda-7 expression constructs into H0-1 and C8161 human melanoma cells reduces growth and inhibits colony formation. These results confirm that mda-7 has antiproliferative properties in human melanoma cells and in this context may contribute to terminal cell differentiation. The mda-7 gene may also function as a negative regulator of melanoma progression.

Amino Acid Sequence↗
PubMed1996

Inhibition of protein kinase C suppresses megakaryocytic differentiation and stimulates erythroid differentiation in HEL cells.

The bisindolylmaleimide, GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide ), a highly selective inhibitor of protein kinase C (PKC), was used to test the role of this enzyme in phorbol ester-induced megakaryocytic differentiation of HEL cells. Treatment of these cells with 10 nmol/L phorbol 12-myristate 13-acetate (PMA) for 3 days caused a complete inhibition of proliferation and a threefold increase in the surface expression of glycoprotein (GP) IIIa, a marker of megakaryocytic differentiation that forms part of the fibrinogen receptor complex, GPIIb/IIIa. A similar effect was observed with phorbol 12,13-dibutyrate, but not with the biologically inactive derivative PMA-4-O-methyl ether. The PMA-induced increase in GPIIIa expression was completely inhibited by GF109203X in a dose-dependent manner (IC50 = 0.5 mumol/L), with a maximal effect at 2.5 to 5.0 mumol/L. GF109203X also blocked the inhibitory effect of PMA on cell growth and inhibited PMA-stimulated phosphorylation of the 47-kD PKC substrate, pleckstrin. Incubation of HEL cells with 25 mumol/L hemin for 3 days caused a fourfold to fivefold increase in expression of the erythroid differentiation marker, glycophorin A. In contrast to the inhibitory effect of GF109203X on GPIIIa expression, hemin induction of glycophorin A was enhanced by this compound. Furthermore, GF109203X alone caused a dose-dependent increase in glycophorin A expression, and induced hemoglobinization. Consistent with these changes, Northern blot analysis revealed that GF109203X treatment reduced the steady-state level of GPIIb mRNA and increased those for glycophorin A and gamma-globin. These results suggest that PKC may act as a developmental switch controlling erythroid/megakaryocytic differentiation.

Aphidicolin↗
PubMed1996

Differential effects of macrophage- and granulocyte-macrophage colony-stimulating factors on cytokine gene expression during rat alveolar macrophage differentiation into multinucleated giant cells (MGC): role for IL-6 in type 2 MGC formation.

Macrophage colony-stimulating factor (M-CSF) and granulocyte-macrophage (GM)-CSF stimulate the differentiation of rat alveolar macrophages (AM) into multinucleated giant cells (MGC) with distinct phenotypes (type 1 and type 2 MGC). In the present study, we analyzed the profile of cytokine gene expression induced respectively, by M-CSF and GM-CSF during rat AM differentiation using reverse transcription-PCR. Enhanced mRNA expression for IL-1alpha, TNF-alpha, and TGF-beta1 was observed 3 h after treatment with M-CSF (50 U/ml) or GM-CSF (50 U/ml). In contrast, IL-6 mRNA expression was increased by GM-CSF but not M-CSF. Kinetic analysis indicated that GM-CSF stimulated IL-6 expression early (1.5 h), with maximal effect observed at 24 h and up to 5 days thereafter. Increased mRNA levels for IL-6 were associated with higher IL-6 activity in the culture media of differentiating AM. IL-6 activity was stimulated 3 h after treatment with GM-CSF and increased with time (up to 5 days). Interestingly, addition of exogenous IL-6 (20-100 ng/ml) alone or in combination with GM-CSF to AM cultures increased slightly and selectively the formation of MGC with type 2 phenotype. Conversely, neutralization of endogenous IL-6 during AM differentiation into MGC inhibited significantly (up to 50%) the formation of type 2 MGC. These results suggest a role for IL-6 in the formation of type 2 MGC and provide some insights into the mechanisms of MGC formation and the processes that regulate it positively.

Animals↗
PubMed1996

Differential intracellular distribution and activities of mu- and m-calpains during the differentiation of human myogenic cells in culture.

Calpains are intracellular calcium-dependent cystein proteases active at neutral pH. There have been found in human adult myogenic cells (i.e. satellite cells) 2 forms of calpains requiring either micromolar Ca2+: mu-calpain, or millimolar Ca2+: m-calpain. Calpains could be involved in both intracellular proteolysis and cytoskeleton reorganization required for myogenic cell fusion. We showed significant differences in calpains distribution during differentiation of myogenic cells. Using mono- and polyclonal antibodies against both types of calpains, we localized mu-calpain and m-calpain in cultured human satellite cells. mu-calpain was detected in the nuclei of myoblasts and in the cytoplasm of myotubes. m-calpain was only present in the cytoplasm, and was concentrated near the nuclear envelope. Biochemical assays for calpain activities showed that the amounts of these proteinases were modulated during cell growth and differentiation. m-calpain activity was high at the proliferation phase (day 4 of culture) and reached a maximum with the beginning of fusion (day 8) and decreased slightly when the number of myotubes increased (day 12). This activity profile suggests that m-calpain could play a role in the initiation of fusion of satellite cells. The activity of mu-calpain increased regularly with cell growth, the maximum being reached when the cells differentiate, i.e. when its intracellular localization shifted from the nucleus to the cytoplasm. We conclude that the activity and the intracellular localization of the 2 forms of calpains differ with the state of differentiation of myogenic cells.

Calpain↗
PubMed1996

Effects of long-term retinoic acid treatment on epidermal differentiation in vivo: specific modifications in the programme of terminal differentiation.

To investigate the effects of long-term all-trans-retinoic acid (RA) treatment on epidermal differentiation in vivo, rhino mice were treated topically with 0.005% RA, and their epidermis was analysed histologically and biochemically after 5, 13 and 26 weeks of treatment. Effects of RA were observed first in the living layers of the epidermis, and then in the non-viable stratum corneum. Five weeks of topical RA led to thickening of the spinous and granular compartments, induction of keratins K6, K16 and K17, and suppression of filaggrin expression. After 13 and 26 weeks of RA treatment, the number of anucleate cornified cell layers remained similar to controls, but additional changes in histology and protein expression were observed. The results showed that prolonged administration of topical RA induced epidermal hyperproliferation, but did not suppress differentiation, in contrast to results observed in keratinocyte cultures. However, the distinct histological and biochemical changes observed in the spinous, granular and cornified layers of RA-treated skin after 26 weeks of treatment, suggested that the progeny of RA-treated basal cells undergo a modified programme of terminal differentiation. Considering the present data together with results of previous in vivo studies, we propose that long-term topical RA treatment retards, or specifically modulates, the later stages in epidermal differentiation, or programmed cell death.

Animals↗
PubMed1996

Differential regulation of human ectocervical epithelial cell line proliferation and differentiation by retinoid X receptor- and retinoic acid receptor-specific retinoids.

Retinoids are important regulators of human papillomavirus (HPV)-immortalized cervical epithelial cell differentiation and have been successfully used in the treatment of HPV-involved cervical cancer. In the present study, we examine the effects of a series of natural and synthetic retinoids on differentiation and proliferation of HPV-16-positive lines, ECE16-1 and CaSki. Retinoic acid receptor alpha (RAR alpha), RAR gamma, and retinoid X receptor alpha (RXR alpha) are the major retinoid receptor subtypes expressed when ECE16-1 cells are grown in retinoid-free medium. Our results indicate that ligands that interact with RARs only or both RARs and RXRs, including all-trans-retinoic acid (all-trans-RA), 9-cis-retinoic acid (9-cis-RA), 13-cis-retinoic acid (13-cis-RA), and several synthetic retinoids, suppress ECE16-1 cell proliferation, regulate expression of the retinoid-responsive differentiation marker cytokeratin K5, and increase RAR beta mRNA levels. In contrast, ligands that specifically interact with RXRs do not suppress proliferation and are less efficient regulators of gene expression. CaSki cells express greatly reduced RAR and RXR levels compared to ECE16-1 cells. However, both RAR- and RXR-specific ligands increase CaSki number by > or = 20%. In addition, RXR-specific ligands suppress cytokeratin K5 mRNA levels slightly, compared to RAR-specific ligands that strongly suppress K5 mRNA levels. We also compare the effects of these agents on the proliferation of other cervical cell lines, including ECE16-D2, ME180, and SiHa cells. ECE16-D2 and ME180 cells are growth suppressed by RAR-specific, but not RXR-specific, retinoids. SiHa cells are not responsive to either class of retinoid. Our results indicate that: (a) the response of different human cervical cell lines varies following treatment with receptor type-specific retinoids; and (b) the relationship between retinoid regulation of proliferation and differentiation can be uncoupled.

Cell Differentiation↗
PubMed1997

Differential expression of low Mr GTP-binding proteins in human megakaryoblastic leukemia cell line, MEG-01, and their possible involvement in the differentiation process.

The expression of various low Mr GTP-binding proteins at various states of differentiation of a human megakaryoblastic leukemia cell line, MEG-01, was analyzed using thermocycle amplification of mRNA and immunoblotting. MEG-01 cells were found to express mRNAs of rap1A, rap1B, rap2B, ralA, rhoA, rac1, rac2, CDC42Hs, rab1, rab3B, rab6, ram and ran, but not rab4, and the proteins of Rap1, Rap2, RhoA, Rac1, Rac2, Rab3B, Rab4, Rab6 and Rab8 were expressed. Differentiation of MEG-01 cells induced by 100 nM 12-O-tetradecanoylphorbol-13-acetate revealed the considerable increases in mRNA expression of rap1B, rab3B, rab4, ram and ran whereas the levels of rap2B, rhoA and rac1 decreased. During the differentiation process, significant changes in protein levels of Rap1, RhoA, Rac1, Rac2, Rab3B, Rab4 and Rab6 were observed among three subcellular (cytosol, Triton X-100-soluble membrane and -insoluble cytoskeleton) fractions. The present investigation may be useful for the study of the megakaryocyte differentiation.

Blood Platelets↗