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Phasevarions mediate random switching of gene expression in pathogenic Neisseria.

Srikhanta YN, Dowideit SJ, Edwards JL, Falsetta ML, Wu HJ, Harrison OB, Fox KL, Seib KL, Maguire TL, Wang AH, Maiden MC, Grimmond SM, Apicella MA, Jennings MP - PLoS Pathog. (2009)

Bottom Line: Phylogenetic studies on phase-variable mod genes associated with type III restriction modification (R-M) systems revealed that these organisms have two distinct mod genes--modA and modB.ModA11 was only found in N. meningitidis and modA13 only in N. gonorrhoeae.Microarray analysis revealed that in all three modA alleles multiple genes were either upregulated or downregulated, some of which were virulence-associated.

View Article: PubMed Central - PubMed

Affiliation: School of Molecular and Microbial Sciences, The University of Queensland, St Lucia, Brisbane, Queensland, Australia.

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, the random switching of the modA gene 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 mod genes are also present in Neisseria meningitidis and Neisseria gonorrhoeae, suggesting that phasevarions may occur in these important human pathogens. Phylogenetic studies on phase-variable mod genes associated with type III restriction modification (R-M) systems revealed that these organisms have two distinct mod genes--modA and modB. There are also distinct alleles of modA (abundant: modA11, 12, 13; minor: modA4, 15, 18) and modB (modB1, 2). These alleles differ only in their DNA recognition domain. ModA11 was only found in N. meningitidis and modA13 only in N. gonorrhoeae. The recognition site for the modA13 methyltransferase in N. gonorrhoeae strain FA1090 was identified as 5'-AGAAA-3'. Mutant strains lacking the modA11, 12 or 13 genes were made in N. meningitidis and N. gonorrhoeae and their phenotype analyzed in comparison to a corresponding mod ON wild-type strain. Microarray analysis revealed that in all three modA alleles multiple genes were either upregulated or downregulated, some of which were virulence-associated. For example, in N. meningitidis MC58 (modA11), differentially expressed genes included those encoding the candidate vaccine antigens lactoferrin binding proteins A and B. Functional studies using N. gonorrhoeae FA1090 and the clinical isolate O1G1370 confirmed that modA13 ON and OFF strains have distinct phenotypes in antimicrobial resistance, in a primary human cervical epithelial cell model of infection, and in biofilm formation. This study, in conjunction with our previous work in H. influenzae, indicates that phasevarions may be a common strategy used by host-adapted bacterial pathogens to randomly switch between "differentiated" cell types.

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Phylogenetic tree inferred from aligned modA genes belonging to a collection of 107 N. meningitidis isolates.More than 500 trees were generated using Clonalframe from which a 95% majority-rule consensus tree was derived and imported into MEGA version 4.0 for further interpretation. (A) Each modA gene was annotated according to clonal complex. (B) Each modA gene was annotated according to the serogroup of the corresponding isolate distinguishing modA12 genes belonging to capsule A meningococci.
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ppat-1000400-g002: Phylogenetic tree inferred from aligned modA genes belonging to a collection of 107 N. meningitidis isolates.More than 500 trees were generated using Clonalframe from which a 95% majority-rule consensus tree was derived and imported into MEGA version 4.0 for further interpretation. (A) Each modA gene was annotated according to clonal complex. (B) Each modA gene was annotated according to the serogroup of the corresponding isolate distinguishing modA12 genes belonging to capsule A meningococci.

Mentions: A complete analysis of modA allele distribution was conducted in N. meningitidis, which has a well characterized population structure defined by multi locus sequence typing (MLST; [18]). The complete 107 strain MLST modA survey revealed that the majority of N. meningitidis strains had either the modA11 or modA12 allele, with modA15 found in two strains and modA4 and modA18 found in one isolate each (Figure 1, Figure 2A and 2B, Table S1). The most notable associations were in capsule type, where 100% of serogroup A strains and 92% of serogroup C strains contained the modA12 allele (Table 1, Figure 2B). Some association with clonal complex was also observed, with meningococci belonging to the ST-32 clonal complex predominantly harbouring the modA11 allele. Further clustering could be seen among ST-41/44 and ST-8 clonal complexes. Unlike N. gonorrhoeae, which contained only one type of modB allele, modB1, N. meningitidis strains contained either modB1 or modB2. There were seven strains, all from the ST-32 group, which contained point mutations in modB1 suggesting the gene is inactive in these strains (Figure 1, Table S1).


Phasevarions mediate random switching of gene expression in pathogenic Neisseria.

Srikhanta YN, Dowideit SJ, Edwards JL, Falsetta ML, Wu HJ, Harrison OB, Fox KL, Seib KL, Maguire TL, Wang AH, Maiden MC, Grimmond SM, Apicella MA, Jennings MP - PLoS Pathog. (2009)

Phylogenetic tree inferred from aligned modA genes belonging to a collection of 107 N. meningitidis isolates.More than 500 trees were generated using Clonalframe from which a 95% majority-rule consensus tree was derived and imported into MEGA version 4.0 for further interpretation. (A) Each modA gene was annotated according to clonal complex. (B) Each modA gene was annotated according to the serogroup of the corresponding isolate distinguishing modA12 genes belonging to capsule A meningococci.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2667262&req=5

ppat-1000400-g002: Phylogenetic tree inferred from aligned modA genes belonging to a collection of 107 N. meningitidis isolates.More than 500 trees were generated using Clonalframe from which a 95% majority-rule consensus tree was derived and imported into MEGA version 4.0 for further interpretation. (A) Each modA gene was annotated according to clonal complex. (B) Each modA gene was annotated according to the serogroup of the corresponding isolate distinguishing modA12 genes belonging to capsule A meningococci.
Mentions: A complete analysis of modA allele distribution was conducted in N. meningitidis, which has a well characterized population structure defined by multi locus sequence typing (MLST; [18]). The complete 107 strain MLST modA survey revealed that the majority of N. meningitidis strains had either the modA11 or modA12 allele, with modA15 found in two strains and modA4 and modA18 found in one isolate each (Figure 1, Figure 2A and 2B, Table S1). The most notable associations were in capsule type, where 100% of serogroup A strains and 92% of serogroup C strains contained the modA12 allele (Table 1, Figure 2B). Some association with clonal complex was also observed, with meningococci belonging to the ST-32 clonal complex predominantly harbouring the modA11 allele. Further clustering could be seen among ST-41/44 and ST-8 clonal complexes. Unlike N. gonorrhoeae, which contained only one type of modB allele, modB1, N. meningitidis strains contained either modB1 or modB2. There were seven strains, all from the ST-32 group, which contained point mutations in modB1 suggesting the gene is inactive in these strains (Figure 1, Table S1).

Bottom Line: Phylogenetic studies on phase-variable mod genes associated with type III restriction modification (R-M) systems revealed that these organisms have two distinct mod genes--modA and modB.ModA11 was only found in N. meningitidis and modA13 only in N. gonorrhoeae.Microarray analysis revealed that in all three modA alleles multiple genes were either upregulated or downregulated, some of which were virulence-associated.

View Article: PubMed Central - PubMed

Affiliation: School of Molecular and Microbial Sciences, The University of Queensland, St Lucia, Brisbane, Queensland, Australia.

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, the random switching of the modA gene 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 mod genes are also present in Neisseria meningitidis and Neisseria gonorrhoeae, suggesting that phasevarions may occur in these important human pathogens. Phylogenetic studies on phase-variable mod genes associated with type III restriction modification (R-M) systems revealed that these organisms have two distinct mod genes--modA and modB. There are also distinct alleles of modA (abundant: modA11, 12, 13; minor: modA4, 15, 18) and modB (modB1, 2). These alleles differ only in their DNA recognition domain. ModA11 was only found in N. meningitidis and modA13 only in N. gonorrhoeae. The recognition site for the modA13 methyltransferase in N. gonorrhoeae strain FA1090 was identified as 5'-AGAAA-3'. Mutant strains lacking the modA11, 12 or 13 genes were made in N. meningitidis and N. gonorrhoeae and their phenotype analyzed in comparison to a corresponding mod ON wild-type strain. Microarray analysis revealed that in all three modA alleles multiple genes were either upregulated or downregulated, some of which were virulence-associated. For example, in N. meningitidis MC58 (modA11), differentially expressed genes included those encoding the candidate vaccine antigens lactoferrin binding proteins A and B. Functional studies using N. gonorrhoeae FA1090 and the clinical isolate O1G1370 confirmed that modA13 ON and OFF strains have distinct phenotypes in antimicrobial resistance, in a primary human cervical epithelial cell model of infection, and in biofilm formation. This study, in conjunction with our previous work in H. influenzae, indicates that phasevarions may be a common strategy used by host-adapted bacterial pathogens to randomly switch between "differentiated" cell types.

Show MeSH
Related in: MedlinePlus