Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Global transcriptomic response of serum-resistant Neisseria meningitidis

ABSTRACT: Neisseria meningitidis remains an important cause of septicemia and meningitis. One of its major virulence traits is its ability to avoid killing by human serum. In the present work, the effect of growth phase (exponential versus stationary) and growth medium (THB versus Catlin) on normal human serum (NHS) sensitivity was assessed on two N. meningitidis serogroup B strains (MC58 and M982). Both strains were found to be dramatically more resistant to 20% NHS killing at early exponential phase than at stationary phase (73-100% survival after 1 to 2 hours of growth compared to less than 10% survival after 7 hours of growth). This growth phase effect was detected only when a rich medium (THB) was used while no such effect was observed using Catlin medium. KDO (2-Keto-3-deoxyoctulosonic acid) and sialic acid content were measured on serum-resistant and serum-sensitive bacteria and were found comparable, indicating that differences in LPS and capsule expression were not at the origin of the observed phenotypes. Transcriptome profiling using a PCR-array was used to compare serum-resistant and serum-sensitive bacteria. A set of 255 genes was found to be differentially expressed with 159 genes up-regulated in serum-resistant bacteria, among them 12 genes involved in glucose catabolism and 22 are known virulence factors. Overall, this study shows that serum-resistant phenotype of N. meningitidis could be obtained through modulating growth conditions. The nature of growth media and growth phases have a major impact on the ability of N. meningitidis to resist to NHS killing. Consequently, the present work underlines the critical importance of carefully controlling those parameters in any studies aimed at investigating the mechanisms and factors involved in N. meningitidis serum-resistance. All experiments were performed in dye swap. These experiments were performed with 2 strains of N. meningitidis serogroup B. In one set of experiments, the gene expression profile of bacteria cultured in THB medium during 7h was compared with the corresponding profile of bacteria cultured during 1h in the same medium. In a second set of experiments, the gene expression profile of 1 strain cultured in THB medium during 7h was compared with the corresponding profile of the same strain cultured in Catlin medium during 7h. 3 biological replicates were performed for each comparison.

ORGANISM(S): Neisseria meningitidis

SUBMITTER: Bachra Rokbi

PROVIDER: E-GEOD-26078 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Adult mouse subventricular zone (SVZ) neural progenitor cells (NPCs) retain the capacity to generate multiple lineages in vitro and in vivo. Thus far, the mechanisms involved in the regulation of these cells have not been well elucidated. We have carried out RNA profiling of adult SVZ cell cultures undergoing differentiation, to identify pathways that regulate progenitor cell proliferation and to define a set of transcripts that can be used as molecular tools in the drug discovery process. We carried out a stepwise stratification of the results to identify transcripts specifically enriched in NPCs and validated some of these using comparative literature analysis, quantitative PCR and immunological techniques. The results show a set of transcription factors, secreted molecules, and plasma membrane markers which are differentially regulated during differentiation. Pathway analysis highlights alterations in IGF, Wnt and TGFbeta signalling cascades. Further characterization of these components could provide greater insight into the mechanisms involved in the regulation of neurogenesis in the adult brain. Mouse subventricular zone neural stem cells cultures were prepared from C57Bl6/J mice (Johansson et al.,1999) and cultured in suspension in DFEM/F12 1:1 supplemented with PSF, B27 supplement and EGF/ FGF-2 at 20ng/ml. RNA was isolated from either expanding neurospheres in the presence of FGF2 and EGF (Reynolds and Weiss, 1992; Gritti et al., 1999), or from cultures induced to differentiate upon growth factor withdrawal or serum exposure, either after 24 hours (in suspension, to avoid changes induced by substrate attachment) or 5 days (as adherent cultures in poly-lysine and laminin-coated plates). Experiments were conducted in triplicate from independent batches of SVZ preparations. As a control for potential effects of media changes, a set of identical cultures were included where cells were grown for a further 24 hours in fresh media containing FGF2 and EGF (20 ng/ml each, normal growth media, NGM). Fluorescently labelled aRNA from individual samples were competitively hybridised against a pool of labelled aRNA from undifferentiated reference (starting) material on custom Agilent microarrays representing ~22,500 mouse transcripts. Technical, fluor-reversed hybridisations were performed for every sample.

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Global transcriptomic response of serum-resistant Neisseria meningitidis

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