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Results for “Phenotypic modulation”

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PubMed1992

Cardiac fibroblasts: function, regulation of gene expression, and phenotypic modulation.

Cardiac fibroblasts constitute the majority of the non-myocyte cell population in the ventricular myocardium. These cells are located in the interstitium, in areas between and surrounding cardiac myocytes. Cardiac fibroblasts are responsible for the synthesis of extracellular matrix proteins such as fibrillar collagen types I and III, basement membrane type IV collagen, fibronectin, and laminin. In addition to its role in muscle development and myoblast differentiations, extracellular matrix consisting primarily of fibrillar collagen is an intricate and highly organized structure that serves to support cardiac myocytes and to maintain functional integrity of the myocardium. Balanced synthesis and degradation of this matrix is the key to normal development of cardiac muscle and perfect myocardial function. Collagen remodeling and accumulation has been demonstrated in several experimental models of cardiac hypertrophy. To gain insights into molecular and cellular mechanisms that affect cardiac fibroblast behavior, cardiac fibroblasts from rat and rabbit ventricular myocardium were cultured and the impact of neurotransmitters and growth factors such as norepinephrine and transforming growth factor--beta (TGF-beta 1), to which cardiac fibroblasts are exposed in vivo, was studied. Results of these studies, with regards to gene expression, proliferation and differentiation of cardiac fibroblasts in culture, and their biological implications are discussed.

Animals↗

PubMed1990

A new assay for invasion of HeLa 229 cells by Bordetella pertussis: effects of inhibitors, phenotypic modulation, and genetic alterations.

Invasion and intracellular survival of Bordetella pertussis in HeLa 229 cells was studied by a new assay that utilizes polymyxin B instead of gentamicin to rapidly kill extracellular organisms. Invasion measured by this assay was time and temperature dependent and was inhibited by the microfilament drug cytochalasin D. The invasion process was also dependent on a functional vir locus (also known as bvg), the positive regulator of virulence gene expression in B. pertussis. Four spontaneous Vir- phase variants of B. pertussis and a mutant with a transposon insertion mutation in the vir locus did not invade. Cells that were environmentally modulated and thus did not express virulence determinants also did not invade. Two Vir- mutants, a vir-directed plasmid insertion mutant and a UV-light-induced mutant, were capable of invasion, although they did not produce other known virulence factors such as pertussis toxin and hemolysin but did produce small amounts of filamentous hemagglutinin (FHA) and the 69-kilodalton outer membrane protein. None of 70 Tn5 IS50L::phoA (TnphoA) insertion mutants of strain Bp18323 (including three mutants defective in FHA) tested showed any reproducible defect in invasion. A mutant carrying a site-directed deletion mutation in FHA was also capable of invasion in our assay. These data suggest that there is redundancy in the invasion functions of B. pertussis and that one or more of these are coordinately regulated with FHA and the 69-kilodalton outer membrane protein more tightly than with other vir-activated gene products.

Bacterial Proteins↗

PubMed1998

Expression of decorin and biglycan by rabbit articular chondrocytes. Effects of cytokines and phenotypic modulation.

In this study, the levels of mRNAs coding for aggrecan, decorin and biglycan in rabbit articular chondrocytes were investigated, using both monolayer and 3D-alginate cultures treated with TGF-beta 1 and IL-1 beta. The cells were shown to express higher amounts of proteoglycan messages, specially the aggrecan, in gels than in monolayers. TGF-beta 1 increased aggrecan mRNA in both systems, whereas biglycan message was elevated only in alginate. It markedly decreased decorin expression in monolayer, either in primary or passaged cultures. In contrast, IL-1 beta had a weak inhibitory effect on both decorin and biglycan expression. Subculturing induced a dramatic decrease of aggrecan mRNA, while that of decorin augmented. Biglycan expression transiently increased after two passages, whereas it declined in further subcultures. Passaged chondrocytes transferred to alginate re-expressed high levels of aggrecan, decorin and biglycan. The data point to the influence of morphology, proliferative state and environment of the articular chondrocytes on their biosynthetic responses to cytokines. Although these immature cells do not fully reflect the adult chondrocytes present in the cartilage, this study may help in understanding the behaviour of these cells in osteoarticular diseases, where the surrounding extracellular matrix is profoundly altered.

Aggrecans↗

PubMed1985

Human endothelial cell cultures: phenotypic modulation by leukocyte interleukins.

We report here that soluble factors from activated mononuclear leukocytes have a dramatic effect on cultured endothelial cells. While human umbilical vein endothelial cells grown under standard conditions show a polygonal, epithelial-like morphology, cells exposed to culture media conditioned by lectin-activated human mononuclear leukocytes become extremely elongated and/or send out numerous cytoplasmic processes, assuming a dendritic configuration. This effect cannot be mimicked by exogenous cyclic AMP, is reversible upon interruption of the treatment, and appears specific for endothelial cells, since it has not been observed so far with other cell types. The shape changes are accompanied by a reorganization of the endothelial cell cytoskeleton: actin microfilament bundles tend to be disposed in parallel arrays, while intermediate filaments and microtubules penetrate up to the extremity of the cytoplasmic processes. Colchicine prevents endothelial cell elongation but only slightly impairs the formation of lateral cell processes ("dendritic configuration"). Purified interleukins were tested for their ability to induce these changes of cell shape. Escherichia coli-recombinant human interleukin 2 had no effect, and gamma-interferon only a slight effect on endothelial cell morphology. Interleukin 1 induced moderate cell elongation, while combined treatment with both interleukin 1 and gamma-interferon resulted in shape changes indistinguishable from those elicited by supernatants of activated mononuclear leukocytes. The possible relevance of the observed endothelial cell changes to the reported angiogenic activity of mononuclear cell products is discussed.

Cells, Cultured↗

PubMed1987

Phenotypic modulation of chronic lymphocytic, prolymphocytic, and lymphoplasmacytic leukemia cells by TPA: induction of TRAP isoenzyme 5 and HD6 (CD22) antigen and enhancement of IgM messenger RNA.

B-cell neoplasias such as CLL can be viewed as models of monoclonal populations restricted within discrete ranges of B-cell maturation. It is unknown whether other B-cell leukemias such as prolymphocytic leukemia (PLL), lymphoplasmacytoid immunocytoma (IC), and hairy cell leukemia (HCL) involve different B lineages or are malignant variants of B cells in successive stages of development along the same lineage. Therefore in vitro maturation was induced with the phorbol ester TPA in leukemic cell samples from 10 CLL, 4 PLL, and 4 IC patients. Morphologically, both plasmacytic and hairy cell-like phenomena were induced. The latter unexpected finding was confirmed by reaction with HD6 (CD22) antibody which stains HCL but is unreactive with plasma cells, multiple myeloma, and CLL cells. Tartrate-resistant acid phosphatase was demonstrated in TPA-cultured CLL, PLL, and IC cells, and the same isoenzyme band as in HCL was revealed by isoelectrofocusing. On the other hand, an increase of IgM messenger RNA was detected in up to 20% of the cells in CLL cultures by single-cell in situ hybridization with fluoro-chrome-labeled DNA probes. An abundance of IgM messenger RNA characterizes lymphoplasmacytoid cells as found in IC. Our data demonstrate that CLL, PLL, and IC can be induced to realize a common genetic program which bears characteristics of HCL indicating that these four entities are more closely related than previously thought.

Acid Phosphatase↗

PubMed1982

Phenotypic modulation of the canine prostate after long-term treatment with androgens and estrogens.

Fine structural alterations of the canine prostate induced by long-term treatment of castrated adult animals with estrogens and/or androgens and also in combination with antiandrogens and/or antiestrogens for six months have been studied with particular respect to their topographic location within the gland. Three major patterns of structural responses of the epithelium have been distinguished: squamous metaplasia, atrophy, and hypertrophy, while in stroma, regression, hypertrophy, or sclerosis were observed. In addition to cellular alterations of stromal fibrocytes and smooth muscle cells, characteristic changes in the arrangement, distribution, and pattern of the different stromal elements occurred. General squamous metaplasia of the epithelium and regressive alterations of stromal cells were most obvious in animals treated with estradiol plus androstanediol. Atrophy of the epithelium and stromal sclerosis were the salient features of antiandrogen-treated castrated animals, while hypertrophy or hyperplasia of both the epithelium and stroma was a major finding in androstanediol-substituted castrated animals. Combined treatment caused rather heterogeneous structural patterns seemingly dependent on the location within the gland. The results indicate that the prostatic epithelial cells dispose of a broad variety of structural reaction patterns that, in case of combined hormonal treatment, are expressed in a manner typical for their locations within the ductal system of the gland. However, with the exception of combined treatment with estradiol, tamoxifen, and androstanediol of castrated dogs, none of the experimental protocols used induced a morphologic response of the gland comparable to that seen in human benign prostatic hyperplasia. The canine prostate therefore is of rather limited value as a model for human BPH.

Androgens↗

PubMed1989

A variant derived from rabbit aortic smooth muscle: phenotype modulation and restoration of smooth muscle characteristics in cells in culture.

We examined the relationship between growth arrest of smooth muscle cells and structural changes in microfilament bundles, and also that between the structural changes and the actions of contractile agonist using a multipassagable variant cell line (SM-3) derived from rabbit aortic smooth muscle cells. The content of smooth muscle type alpha-actin increased with density-dependent growth arrest of the SM-3 cells, but was attenuated in the logarithmically growing cultures. As assessed cytochemically, the growth-arrested cells contained longitudinally oriented bundles of actin-containing microfilament and myosin-based filaments visualized with rhodamine-phalloidin and antibody against myosin light chain 20, respectively, whereas both actin- and myosin-containing structures in logarithmically growing cells showed slight, shortened, or diffused patterns. Electron microscopic examination of the growth-arrested cells revealed that the cells contained numerous and conspicuous microfilament bundles associated with many compact electron-dense bodies. In addition, pinocytotic vesicles were often found near the plasma membrane in the growth-arrested cells. SM-3 cells in the growth-arrested phase responded to prostaglandin F2 alpha (3-30 microM) and rat endothelin (0.1-1.0 microM) with a reversible contractile response, in association with monophosphorylation and/or diphosphorylation of the myosin light chain 20. However, the influence of the contractile agonists was greatly reduced during logarithmic growth. These results suggest that in the SM-3 cells in the growth-arrested phase, there is a restoration of the contractile architecture and the myosin light chain phosphorylation system. Thus, this SM-3 cell line is expected to serve as a useful model for examining biochemical and physiological phenomena of smooth muscle.

Actins↗

PubMed2005

Patterns of gene expression differentially regulated by platelet-derived growth factor and hypertrophic stimuli in vascular smooth muscle cells: markers for phenotypic modulation and response to injury.

In vascular smooth muscle cells (VSMC), platelet-derived growth factor (PDGF) suppresses expression of multiple smooth muscle contractile proteins, useful markers of differentiation. Conversely, hypertrophic agents induce expression of these genes. The goal of this study was to employ genomic approaches to identify classes of genes differentially regulated by PDGF and hypertrophic stimuli. Changes in gene expression were determined using Affymetrix RAE-230 GeneChips in rat aortic VSMC stimulated with PDGF. For comparison with a model hypertrophic stimulus, a microarray was performed with VSMC stably expressing constitutively active Galpha(16), which strongly induces smooth muscle marker expression. We identified 75 genes whose expression was increased by exposure to PDGF and decreased by expression of Galpha(16) and 97 genes whose expression was decreased by PDGF and increased by Galpha(16). These genes included many smooth muscle-specific proteins; several extracellular matrix, cytoskeletal, and chemotaxis-related proteins; cell signaling molecules; and transcription factors. Changes in gene expression for many of these were confirmed by PCR or immunoblotting. The contribution of signaling pathways activated by PDGF to the gene expression profile was examined in VSMC stably expressing gain-of-function H-Ras or myristoylated Akt. Among the genes that were confirmed to be differentially regulated were CCAAT/enhancer-binding protein delta, versican, and nexilin. All of these genes also had altered expression in injured aortas, consistent with a role for PDGF in the response of injured VSMC. These data indicate that genes that are differentially regulated by PDGF and hypertrophic stimuli may represent families of genes and potentially be biomarkers for vascular injury.

Animals↗

PubMed1993

Phenotypic modulation of human hair matrix cells (trichocytes) by environmental influence in vitro and in vivo.

Trichocytes, i.e. precursor cells of the hair cortex and medulla, isolated from plucked human scalp hair follicles (HF) were propagated on feeder layers of post-mitotic human dermal fibroblasts (HDF). Cell isolates from five HF routinely yielded about 0.5-1 x 10(5) cells within 3 weeks. When grown as 'surface epithelia' in vitro (on dermal equivalents exposed to air), trichocytes organized into stratified epithelia largely reminiscent of epidermis with regard to both tissue architecture and localization of epidermal differentiation products (keratins K1 and K10, involucrin, filaggrin). However, when HDF in the collagen matrix were replaced by dermal papilla cells (DPC) epidermoid differentiation was largely prevented while still allowing growth and stratification. Epidermal differentiation (keratinization) was virtually complete when trichocytes grown on collagen gels with HDF were transplanted onto nude mice; this was apparent by tissue organization, expression of K1 and K10 and the nearly regular epidermal localization of involucrin. In addition, the deposition of basement membrane components (laminin, type IV collagen, bullous pemphigoid antigen) at the epithelium-collagen interface further increased and was more regular in transplants than in vitro. Cells embedded in Matrigel together with HDF developed large spheroidal structures with inward-directed differentiation and all the epidermal markers found in 'surface' cultures, while only small keratinizing spheroids formed without HDF. In this system co-culture of trichocytes with DPC suppressed almost completely epidermal keratinization. Although typical hair proteins were not detectable, our data clearly demonstrate that: (1) bona fide trichocytes inherit the options for alternative directions of differentiation, and (2) external (in part mesenchymal cell-mediated) influences play a pivotal role in this determination.

Animals↗

PubMed2003

The HLA-DR phenotype modulates the humoral immune response to enterovirus antigens.

AIMS/HYPOTHESIS: Enterovirus infections are among the environmental risk factors potentially contributing to the pathogenesis of Type 1 diabetes. The aim of this study was to evaluate virus-host interaction by analysing the enterovirus antibody levels in subjects carrying different HLA-DR alleles associated with either increased or decreased risk of Type 1 diabetes. METHODS: Antibodies against coxsackievirus B4 were measured to study immune responses induced by natural enterovirus infections and against poliovirus 1 to study immune responses induced by immunisation by enterovirus antigens (vaccine). Antibodies against the mumps virus were measured as a control. Study subjects included siblings of children with Type 1 diabetes taking part in the Childhood Diabetes in Finland (DiMe) Study and carrying either HLA-DR risk (DR3 and/or DR4) or protective (DR2) alleles. RESULTS: Children with either the HLA-DR3 or HLA-DR4 allele and those with both these risk alleles had higher Coxsackie B4 antibody levels than children carrying the HLA-DR2 allele ( p=0.01, p=0.01 and p=0.008, respectively). High responders (IgG levels higher than 75 percent) were also more frequent among genetically susceptible children compared to children with the protective DR2 allele (27% vs 12%) ( p<0.009). The same trend was seen for poliovirus antibodies, while mumps antibody levels had a different pattern (high responders more common among DR2-positive subjects). CONCLUSIONS/INTERPRETATION: Diabetes-associated HLA-DR risk alleles were associated with a strong immune responsiveness and protective alleles with a weak responsiveness against enterovirus antigens. This phenomenon should be taken into consideration in serological case-control studies and it might play a role in virus-induced beta-cell damage.

Antibody Formation↗

PubMed1987

Isolation of rat aortic endothelial cells by primary explant techniques and their phenotypic modulation by defined substrata.

An efficient and reliable procedure for the isolation and culture of endothelium from large vessels of small animals (e.g., rat) is described, which takes advantage of endothelial cell-extracellular matrix interactions to promote the outgrowth of cells from tissue explants. The procedure may also permit the isolation by nonenzymatic means, of endothelial cells from other vessels and tissues. Rings and opened segments of aortic tissue were placed on a variety of substrates including: untreated tissue culture plastic; films of fibronectin, laminin, type I collagen, and gelatin; gels of type I collagen (Vitrogen, Collagen Corporation, Palo Alto, California), of basement membrane components derived from the EHS sarcoma (Matrigel, Collaborative Research Inc., Lexington, Massachusetts), and of agar and agarose. The medium used was OPTI-MEM or RPMI 1640 (Gibco Laboratories, Grand Island, New York) with 3% or 20% fetal calf serum, and 50 micrograms/ml endothelial cell growth supplement. Only explants on Vitrogen and on Matrigel produced a significant and consistent outgrowth of cells and this occurred shortly after the initiation of explants. Virtually no outgrowth occurred from explants on the other substrata, even after 10 days in culture. On Vitrogen gels, the cells emerged from the explants as single stellate and bipolar cells, whereas those on Matrigel grew as chains and sheets from the edges of the explant. Cells were passaged from both types of gels onto plastic or glass surfaces. The passaged cells isolated from both gel matrices exhibited specific endothelial cell characteristics including a "cobbled" morphology at confluence, positive staining for von Willebrand factor, and uptake of Di-I-Ac-low density lipoprotein. Because rat and other small animal aortic endothelial cells are resistant to isolation by enzymatic treatment, this technique provides a simple means to obtain large numbers of this cell type. Further, the method permits study of endothelial cell functions in vitro, and the roles which the extracellular matrix may play in these processes.

Animals↗

PubMed1995

Phenotypic modulation of newly synthesized proteoglycans in human cartilage and chondrocytes.

The proteoglycans synthesized by human osteoarthritic femoral head cartilage and nonarthritic articular cartilage age-matched to the osteoarthritic cartilage specimens was studied in explant cultures and in chondrocytes generated by explant outgrowth from the cartilages. Twenty-four hours after explanation, both nonarthritic articular cartilage and osteoarthritic cartilage synthesized principally one large proteoglycan core protein that migrated on 3-5% acrylamide gels with an apparent molecular mass (M(r)) of approximately 520 kDa after enzymatic digestion with chondroitinase ABC and keratanase. The proteoglycan was found in both the explant itself and in the medium compartment of the culture as well. This proteoglycan contained chondroitin-6-sulfate, keratan sulfate and the hyaluronan binding region as evidenced by immunoblotting with murine anti-proteoglycan monoclonal antibodies indicating that the proteoglycan was aggrecan. To a much lesser extent two additional proteoglycan core proteins were also found in the explant but were not seen in the culture medium compartment. These proteoglycans possessed apparent M(r)'s of approximately 480 kDa and approximately 390 kDa on 3-5% acrylamide gels after chondroitinase ABC and keratanase digestion. The medium compartment contained principally the approximately 520 kDa proteoglycan core protein. In osteoarthritic cartilage explants, the pattern of newly synthesized proteoglycans recovered from the tissue as assessed on 3-16% polyacrylamide gradient gels remained relatively the same from day 1 after explantation up to 36 days of culture. By contrast, the proteoglycans recovered from the culture medium contained chondroitin sulfate and keratan sulfate after 1, 7, and 21 days in culture but by 36 days appeared to contain only chondroitin sulfate. Chondrocytes generated from osteoarthritic cartilage and age-matched nonarthritic articular cartilage synthesized different patterns of large (greater than 200 kDa) proteoglycan. Whereas chondrocytes derived from osteoarthritic cartilage continued to synthesize principally the approximately 520 kDa proteoglycan core protein, the chondrocytes derived from nonarthritic cartilage synthesized in addition to this proteoglycan, abundant amounts of the other two proteoglycan core proteins as well.

Age Factors↗

PubMed1997

Reconstitution of the NF-kappa B system in Saccharomyces cerevisiae for isolation of effectors by phenotype modulation.

NF-kappa B is a ubiquitous transcription factor that contributes to the induction of many genes playing a central role in immune and inflammatory responses. The NF-kappa B proteins are subject to multiple regulatory influences including post-translational modifications such as phosphorylation and proteolytic processing. A very important component of this regulation is the control of their subcellular localization: cytoplasmic retention of NF-kappa B is achieved through interaction with I kappa B molecules. In response to extracellular signals, these molecules undergo degradation, NF-kappa B translocates to the nucleus and activates its target genes. To investigate novel proteins involved in this dynamic response, we have reconstituted the NF-kappa B/I kappa Beta system in the yeast Saccharomyces cerevisiae. We have successively introduced p65, the main transcriptional activator of the NF-kappa B family, which leads to the activation of two reporter genes controlled by kappa B sites, and the I kappa B alpha inhibitory protein, which abolishes this activation. By transforming such a yeast strain with a cDNA library we have performed a genetic screen for cDNAs encoding proteins capable of either dissociating the p65/I kappa B alpha complex or directly transactivating the expression of the reporter genes. The efficiency of our screen was demonstrated by the isolation of a cDNA encoding the p105 precursor of the p50 subunit of NF-kappa B. We also used this system to test stimuli known to activate signalling pathways in yeast, in order to investigate whether the related mammalian cascades might be involved in NF-kappa B activation. We showed that yeast endogenous kinase cascades activated by pheromone, hypo- or hyperosmotic shock cannot modulate NF-kappa B activity in our system, and that the p38 human MAP kinase does not act directly on the p65/I kappa B alpha complex.

DNA, Complementary↗

PubMed2000

Phenotypic modulation of neointimal smooth muscle cells during the evolution of transplant renal arteriosclerosis determined via myosin heavy chain expression.

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Adolescent↗

PubMed2000

Early treatment with corticosteroids ameliorates proteinuria, proliferative lesions, and mesangial phenotypic modulation in adult diffuse proliferative IgA nephropathy.

Diffuse proliferative immunoglobulin A (IgA) nephropathy has the potential risk for end-stage renal disease. However, treatment of IgA nephropathy has not been well established. To determine whether early treatment with corticosteroids ameliorates the proliferative lesions of diffuse proliferative IgA nephropathy, we conducted a prospective, randomized, controlled trial. Inclusion criteria were as follows: duration of abnormal urinalysis results less than 36 months, proteinuria less than 1.5 g/d of protein, serum creatinine level less than 1.5 mg/dL, and mesangial cell proliferation or matrix accumulation involving more than 50% of glomeruli. Twenty-one patients were randomly assigned to two groups: the corticosteroid group and the antiplatelet group. After 1 year of treatment, repeated renal biopsy was performed in 19 patients. We evaluated glomerular filtration rate, blood pressure, proteinuria, and histological parameters, including light microscopic findings and staining of alpha-smooth muscle actin (alphaSMA), as a marker of myofibroblast-like cells and fibronectin EDA (EDA-FN) as an indicator of renal fibrosis. After 1 year of treatment, proteinuria significantly decreased in the corticosteroid group. Histological findings, such as mesangial cell proliferation, mesangial matrix accumulation, and cellular crescents, showed significant improvement in the corticosteroid group but not in the antiplatelet group. Expression of alphaSMA in glomeruli significantly decreased in the corticosteroid group but not in the antiplatelet group. EDA-FN did not change in either group. We conclude that early treatment with corticosteroids for adult diffuse proliferative IgA nephropathy is effective in reducing renal injury.

Adult↗

PubMed1999

Intermediate stages in monocyte-macrophage differentiation modulate phenotype and susceptibility to virus infection.

The kinetics of monocyte-macrophage differentiation was analysed using two Swine Workshop Cluster (SWC) CD molecules: SWC1 and SWC9. Myeloid cells were selected by labelling for the common myeloid antigen, SWC3. Confirmation of macrophage identification used acid phosphatase and phagocytosis activities. During differentiation, SWC1 was gradually lost. SWC9 was absent on monocytes but up-regulated early. Consequently, monocytes were SWC1+ SWC9- and macrophages were SWC1- SWC9+. An additional, intermediate, cell population was identified as SWC1+ SWC9+. Size and granularity characteristics mirrored the monocyte, macrophage and intermediate-cell phenotypes. Overall, SWC9 up-regulation was central in macrophage differentiation and dependent on plasma factors. The concomitant loss of SWC1 was independent of these factors, but always associated with mature macrophages. Upon up-regulation of SWC9, the SWC1+ SWC9+ intermediate monocytic cells became susceptible to African swine fever virus infection. These results demonstrate the heterogeneity of monocytic cell differentiation and the importance of these characteristics for interaction with monocytotropic viruses.

African Swine Fever↗

PubMed2003

A transgene carrying an A2G missense mutation in the SMN gene modulates phenotypic severity in mice with severe (type I) spinal muscular atrophy.

5q spinal muscular atrophy (SMA) is a common autosomal recessive disorder in humans and the leading genetic cause of infantile death. Patients lack a functional survival of motor neurons (SMN1) gene, but carry one or more copies of the highly homologous SMN2 gene. A homozygous knockout of the single murine Smn gene is embryonic lethal. Here we report that in the absence of the SMN2 gene, a mutant SMN A2G transgene is unable to rescue the embryonic lethality. In its presence, the A2G transgene delays the onset of motor neuron loss, resulting in mice with mild SMA. We suggest that only in the presence of low levels of full-length SMN is the A2G transgene able to form partially functional higher order SMN complexes essential for its functions. Mild SMA mice exhibit motor neuron degeneration, muscle atrophy, and abnormal EMGs. Animals homozygous for the mutant transgene are less severely affected than heterozygotes. This demonstrates the importance of SMN levels in SMA even if the protein is expressed from a mutant allele. Our mild SMA mice will be useful in (a) determining the effect of missense mutations in vivo and in motor neurons and (b) testing potential therapies in SMA.

Animals↗

PubMed2002

A new chromosomal locus associated with gut-modulated phenotypes in Salmonella enterica serotype typhimurium.

A cosmid DNA library had been constructed previously from 40-kb fragments of genomic DNA from a virulent invasive strain of Salmonella enterica serotype Typhimurium (TML) in an avirulent hypo-invasive Typhimurium strain (LT7). Selection of invasive clones from the library was attempted by iterative passage through a rabbit ileal organ culture. After the fourth passage, a clone, designated LT7(pHC20-2), was isolated. Exposure to both gut tissue and Caco-2 cells enhanced the growth, invasiveness for gut and Caco-2 cells, and flagellin expression of LT7(pHC20-2) although its invasiveness was less than that of strain TML. Expression of appendages (surface structures c. 60-70 nm diameter) was shown to play a role in but not to confer invasiveness, and was demonstrated in the absence of direct contact with eukaryotic cells. Exposure to gut tissue also affected the expression of several outer-membrane proteins (OMPs) in all four Salmonella strains--TML, LT7, LT7(pHC79), LT7(pHC20 2)--used in this work. As the genes involved in flagella, invasin and porin expression are distributed around the salmonella chromosome, it is possible that pHC20-2 encodes a pleiotropic regulator of genes involved in gastro-enteritic virulence and adaptation to the in-vivo gut environment. pHC20-2 mapped at c. centisome 25 on the salmonella chromosome close to, but distinct from, SPI-5.

Adhesins, Bacterial↗