The complete genome sequence and comparative genome analysis of the high pathogenicity Yersinia enterocolitica strain 8081

The human enteropathogen, Yersinia enterocolitica, is a significant link in the range of Yersinia pathologies extending from mild gastroenteritis to bubonic plague. Comparison at the genomic level is a key step in our understanding of the genetic basis for this pathogenicity spectrum. Here we report the genome of Y. enterocolitica strain 8081 (serotype 0:8; biotype 1B) and extensive microarray data relating to the genetic diversity of the Y. enterocolitica species. Our analysis reveals that the genome of Y. enterocolitica strain 8081 is a patchwork of horizontally acquired genetic loci, including a plasticity zone of 199 kb containing an extraordinarily high density of virulence genes. Microarray analysis has provided insights into species-specific Y. enterocolitica gene functions and the intraspecies differences between the high, low, and nonpathogenic Y. enterocolitica biotypes. Through comparative genome sequence analysis we provide new information on the evolution of the Yersinia. We identify numerous loci that represent ancestral clusters of genes potentially important in enteric survival and pathogenesis, which have been lost or are in the process of being lost, in the other sequenced Yersinia lineages. Our analysis also highlights large metabolic operons in Y. enterocolitica that are absent in the related enteropathogen, Yersinia pseudotuberculosis, indicating major differences in niche and nutrients used within the mammalian gut. These include clusters directing, the production of hydrogenases, tetrathionate respiration, cobalamin synthesis, and propanediol utilisation. Along with ancestral gene clusters, the genome of Y. enterocolitica has revealed species-specific and enteropathogen-specific loci. This has provided important insights into the pathology of this bacterium and, more broadly, into the evolution of the genus. Moreover, wider investigations looking at the patterns of gene loss and gain in the Yersinia have highlighted common themes in the genome evolution of other human enteropathogens

Homology between a genetic locus ( mdoA ) involved in the osmoregulated biosynthesis of periplasmic glucans in Escherichia coli and a genetic locus ( hrpM ) controlling pathogenicity of Pseudomonas syringae

International audienceMembrane-derived oligosaccharides (MDO) of Escherichia coli are representative members of a family of glucans found in the periplasmic space of Gram-negative bacteria. The two genes forming the mdoGH operon are necessary for the synthesis of MDO. The nucleotide sequence (4759 bp) and the transcriptional start of this operon were determined. Both gene products were further characterized by gene fusion analysis. MdoG is a 56 kDa periplasmic protein whose function remains to be determined. MdoH, whose presence was shown to be necessary for normal glucosyl transferase activity, is a 97 kDa protein spanning the cytoplasmic membrane. To our surprise, these proteins are not homologous to the periplasmic gtucan biosynthetic enzymes previously characterized in the Rhizobiaceae family. However, a considerable homology (69% identical nucleotides out of 2816) was discovered between mdoGH and the two genes present at the hrpM locus of the phytopathogenic bacterium Pseudomonas syringae pv. syringae. Functions of these genes remain mysterious but they are known to be required for both the expression of disease symptoms on host plants and the development of the hypersensitive reaction on non-host plants (Mills and Mukhopadhyay, 1990). These results confirm the importance of periplasmic glucans for the physiological ecology of Gram-negative bacteria

Genome Toxicity and Impaired Stem Cell Function after Conditional Activation of CreERT2 in the Intestine

Summary: With the tamoxifen-inducible CreERT2 system, genetic recombination can be temporally controlled in a cell-type-specific manner in intact animals, permitting dissection of the molecular underpinnings of mammalian physiology. Here we present a significant drawback to CreERT2 technology for analysis of intestinal stem cells. Using the intestine-specific Villin-CreERT2 mouse strain, we observed delayed intestinal regeneration post irradiation. Villin-CreERT2 activation was associated with DNA damage and cryptic loxP site cleavage. Analysis of stem cell-specific CreERT2 strains showed that the genome toxicity impairs function of crypt base columnar stem cells, resulting in loss of organoid initiating activity. Importantly, the stem cell impairment is short-lived, with return to normal by 7 days post tamoxifen treatment. Our findings demonstrate that mouse genetic experiments that utilize CreERT2 should consider the confounding effects of enhanced stem cell sensitivity to genome toxicity resulting from CreERT2 activation. : Samuelson and colleagues demonstrate that activation of CreERT2 in the mouse intestine leads to intestinal stem cell (ISC) toxicity. Impaired stem cell function was shown by reduced organoid-forming ability in ISC-CreERT2 strains. Also, Villin-CreERT2 mice exhibited impaired crypt regeneration after ISC injury induced by γ-irradiation. DNA damage due to cryptic loxP site cleavage suggested a mechanism of ISC genotoxicity. Keywords: intestinal stem cell, organoid, CreERT2, loxP, genotoxicity, tamoxifen, mouse, crypt regeneratio

Objectivation des modifications cutanées liées au vieillissement par une technique d'imagerie non invasive de la peau : la microscopie multiphoton in vivo

Hors-Série 3 - Journées dermatologiques de Paris 2012National audienc

[Characterization of gonadotropic cells in a new pituitary tumor cell line]

The pituitary tumor cell line RC-4B/C was established in The Jackson Laboratory from an aged rat pituitary adenoma. Immunocytochemical studies of this cell line showed that all pituitary cell types were present. Approximately 20% reacted with antisera (AS) to ovine (o) LH beta, 8.6% with AS to oFSH beta, 15% with AS to rat PRL, 12% with AS to equine GH, 9% with AS to porcine TSH beta and 8.6% with AS to ACTH1-24. Using NIDDK rat kits, RIA showed about 0.38, 0.08 and 607.50 ng per 10(6) cells of LH, FSH and PRL, respectively, vs 33.9, 75.6 and 573 ng in freshly dispersed rat pituitary cells. The GnRH receptor content of the cell line was about a half that of normal rat pituitary cells but the receptor affinity was the same. A chronic treatment of the cells for about 5 months with a sub-physiological: concentration (3.7 pM) of a GnRH agonist had 3 major effects: 1) as compared to the controls, a 3-fold increase in the cell number in the log phase; 2) an increase of the percentage of FSH beta cells from 8.6 to 21.9% whereas LH beta cells and the cell content of LH and FSH remained stationary; 3) a decrease of the percentage of PRL cells from 15 to 6.5% and an almost 250-fold decrease of PRL cell content. Incorporation studies with [35S] Met demonstrated that the alpha subunit in the cell line was only partly glycosylated. Pretreatment of the cells with 5 nM estradiol restored, at least partly, glycosylation of alpha.(ABSTRACT TRUNCATED AT 250 WORDS

Objectivation des modifications cutanées cortico-induites en fonction de l'âge

Hors-Série 3 - Journées dermatologiques de Paris 2012National audienc