title: ModM DNA methyltransferase methylome analysis reveals a potential role for Moraxella catarrhalis phasevarions in otitis media.
abstract: Moraxella catarrhalis is a significant cause of otitis media and exacerbations of chronic obstructive pulmonary disease. Here, we characterize a phase-variable DNA methyltransferase (ModM), which contains 5'-CAAC-3' repeats in its open reading frame that mediate high-frequency mutation resulting in reversible on/off switching of ModM expression. Three modM alleles have been identified (modM1-3), with modM2 being the most commonly found allele. Using single-molecule, real-time (SMRT) genome sequencing and methylome analysis, we have determined that the ModM2 methylation target is 5'-GAR(m6)AC-3', and 100% of these sites are methylated in the genome of the M. catarrhalis 25239 ModM2 on strain. Proteomic analysis of ModM2 on and off variants revealed that ModM2 regulates expression of multiple genes that have potential roles in colonization, infection, and protection against host defenses. Investigation of the distribution of modM alleles in a panel of M. catarrhalis strains, isolated from the nasopharynx of healthy children or middle ear effusions from patients with otitis media, revealed a statistically significant association of modM3 with otitis media isolates. The modulation of gene expression via the ModM phase-variable regulon (phasevarion), and the significant association of the modM3 allele with otitis media, suggests a key role for ModM phasevarions in the pathogenesis of this organism.
authors.affiliation: Institute for Glycomics and.
authors.forename: Luke V
authors.initials: LV
authors.lastname: Blakeway
authors.affiliation: Institute for Glycomics and.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Power
authors.affiliation: Institute for Glycomics and.
authors.forename: Freda E-C
authors.initials: FE
authors.lastname: Jen
authors.affiliation: Institute for Glycomics and.
authors.forename: Sam R
authors.initials: SR
authors.lastname: Worboys
authors.affiliation: Pacific Biosciences, Menlo Park, California, USA; and.
authors.forename: Matthew
authors.initials: M
authors.lastname: Boitano
authors.affiliation: Pacific Biosciences, Menlo Park, California, USA; and.
authors.forename: Tyson A
authors.initials: TA
authors.lastname: Clark
authors.affiliation: Pacific Biosciences, Menlo Park, California, USA; and.
authors.forename: Jonas
authors.initials: J
authors.lastname: Korlach
authors.affiliation: Center for Microbial Pathogenesis, Research Institute at Nationwide Children's Hospital, Columbus, Ohio, USA.
authors.forename: Lauren O
authors.initials: LO
authors.lastname: Bakaletz
authors.affiliation: Institute for Glycomics and.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jennings
authors.affiliation: Institute for Glycomics and School of Medical Science, Griffith University, Southport, Queensland, Australia;
authors.forename: Ian R
authors.initials: IR
authors.lastname: Peak
authors.affiliation: Institute for Glycomics and k.seib@griffith.edu.au.
authors.forename: Kate L
authors.initials: KL
authors.lastname: Seib
mesh_terms: D000595:Amino Acid Sequence; D015254:DNA Modification Methylases / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D001936:Moraxella catarrhalis / Q000472:pathogenicity*; D045828:Moraxellaceae Infections / Q000201:enzymology / Q000382:microbiology*; D010033:Otitis Media / Q000201:enzymology / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D015254:DNA Modification Methylases
keywords: SMRT; epigenetic regulation; middle ear infection; phase variation; single-molecule, real-time genome sequencing