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Phasevarion mediated random switching of gene expression in Helicobacter Pylori

ABSTRACT: Many host-adapted bacterial pathogens contain DNA methyltransferases (mod genes) that are subject to phase-variable expression (high-frequency reversible ON/OFF switching of gene expression). In Haemophilus influenzae, Neissera Meningtidis and Neisseria Gonorrhoeae, the random switching of the modA gene, associated with a phase variable type III restriction modification (R-M) system, controls expression of a phase-variable regulon of genes (a “phasevarion”), via differential methylation of the genome in the modA ON and OFF states. Phase variable type III R-M systems are also found in Helicobacter pylori, suggesting that phasevarions may also exist in this intriguing pathogen. Phylogenetic studies on the phase-variable type III modC gene revealed that there are 12 distinct alleles in H. pylori, which differ only in their DNA recognition domain, with the majority containing the C5 allele. Microarray analysis comparing the H. pylori wild-type P12modC5 ON strain to the P12(delta)modC5 mutant revealed that six genes were either up-regulated or down-regulated, some of which were virulence-associated. For example flaA, which encodes a flagella protein important in motility and hopG, which encodes an important outer membrane protein. This study, in conjunction with our previous work, indicates that phasevarions may be a common strategy used by host-adapted bacterial pathogens to randomly switch between “differentiated” cell types.

ORGANISM(S): Helicobacter pylori Helicobacter pylori P12

PROVIDER: GSE26759 | GEO | 2012/01/16

SECONDARY ACCESSION(S): PRJNA136307

REPOSITORIES: GEO

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Project description:In this study, a whole-genome CombiMatrix Custom oligonucleotide tiling microarray with 90000 probes covering six sequenced Helicobacter pylori(H. pylori) genomes was designed and utilized for comparative genomic profiling of eight unsequenced strains isolated from patients with different gastroduodenal diseases in Heilongjiang province of China. Since significant genomic variation were found among these strains, an additional 76 H. pylori stains with different clinical outcomes isolated from various provinces of China were further tested by PCR to demonstrate this distinction. We observed several highly variable regions among strains of gastritis, gastric ulceration and gastric cancer. They are involved in genes associated with bacterial type I, type II and type III R-M system as well as in a virB gene neighboring the well studied cag pathogenic island. Previous studies have reported the diverse genetic characterization of this pathogenic island, but it is conserved in the strains tested by microarray in this study. Moreover, a number of genes involved in the type IV secretion system related to DNA horizontal transfer between H. pylori strains were identified based on the comparative analysis of the strain specific genes. These findings may provide new insights for discovering biomarkers for prediction of gastric diseases. Here we describe the design and use of a high-density oligonucleotide microarray covering six sequenced H. pylori genomes as well as several sequenced plasmids. The performance of this microarray is evaluated, and its utility is illustrated for the hybridization of genomic DNA in order to compare eight uncharacterized H. pylori strains which have not been sequenced with the six known, sequenced strains. We utilize this microarray to identify variable genomic region among H. pylori strains isolated from patients with different gastroduodenal diseases in a Chinese patient population. H. pylori isolates from 2 patients with chronic superficial gastritis, 2 patients with atrophic gastritis, 2 patients with gastric ulcer, and 2 patients with gastric cancer were studied. All eight strains were isolated from Heilongjiang province of China. A number of variable regions with high genetic diversity was identified. 26 selected genes were validated by large scale PCR in both microarray tested strains while an additional 76 strains were isolated from eight provinces.

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Phasevarion mediated random switching of gene expression in Helicobacter Pylori

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