title: Genome-wide DNA methylation profiling in rheumatoid arthritis identifies disease-associated methylation changes that are distinct to individual T- and B-lymphocyte populations.
abstract: Changes to the DNA methylome have been described in patients with rheumatoid arthritis (RA). In previous work, we reported genome-wide methylation differences in T-lymphocyte and B-lymphocyte populations from healthy individuals. Now, using HumanMethylation450 BeadChips to interrogate genome-wide DNA methylation, we have determined disease-associated methylation changes in blood-derived T- and B-lymphocyte populations from 12 female patients with seropositive established RA, relative to 12 matched healthy individuals. Array data were analyzed using NIMBL software and bisulfite pyrosequencing was used to validate array candidates. Genome-wide DNA methylation, determined by analysis of LINE-1 sequences, revealed higher methylation in B-lymphocytes compared with T-lymphocytes (P ≤ 0.01), which is consistent with our findings in healthy individuals. Moreover, loci-specific methylation differences that distinguished T-lymphocytes from B-lymphocytes in healthy individuals were also apparent in RA patients. However, disease-associated methylation differences were also identified in RA. In these cases, we identified 509 and 252 CpGs in RA-derived T- and B-lymphocytes, respectively, that showed significant changes in methylation compared with their cognate healthy counterparts. Moreover, this included a restricted set of 32 CpGs in T-lymphocytes and 20 CpGs in B-lymphocytes (representing 15 and 10 genes, respectively, and including two, MGMT and CCS, that were common to both cell types) that displayed more substantial changes in methylation. These changes, apparent as hyper- or hypo-methylation, were independently confirmed by pyrosequencing analysis. Validation by pyrosequencing also revealed additional sites in some candidate genes that also displayed altered methylation in RA. In this first study of genome-wide DNA methylation in individual T- and B-lymphocyte populations in RA patients, we report disease-associated methylation changes that are distinct to each cell type and which support a role for discrete epigenetic regulation in this disease.
authors.affiliation: Institute for Science and Technology in Medicine; Keele University; Guy Hilton Research Centre; Stoke-on-Trent, Staffordshire UK; Haywood Rheumatology Centre; Haywood Hospital; Stoke-on-Trent, Staffordshire UK.
authors.forename: John R
authors.initials: JR
authors.lastname: Glossop
authors.affiliation: School of Veterinary Medicine and Science; University of Nottingham; Sutton Bonington, Leicestershire UK; Advanced Data Analysis Centre; University of Nottingham; Sutton Bonington, Leicestershire UK.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Emes
authors.affiliation: Haywood Rheumatology Centre; Haywood Hospital; Stoke-on-Trent, Staffordshire UK.
authors.forename: Nicola B
authors.initials: NB
authors.lastname: Nixon
authors.affiliation: Institute for Science and Technology in Medicine; Keele University; Guy Hilton Research Centre; Stoke-on-Trent, Staffordshire UK.
authors.forename: Kim E
authors.initials: KE
authors.lastname: Haworth
authors.affiliation: Haywood Rheumatology Centre; Haywood Hospital; Stoke-on-Trent, Staffordshire UK.
authors.forename: Jon C
authors.initials: JC
authors.lastname: Packham
authors.affiliation: Haywood Rheumatology Centre; Haywood Hospital; Stoke-on-Trent, Staffordshire UK.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Dawes
authors.affiliation: Institute for Science and Technology in Medicine; Keele University; Guy Hilton Research Centre; Stoke-on-Trent, Staffordshire UK.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Fryer
authors.affiliation: Institute for Science and Technology in Medicine; Keele University; Guy Hilton Research Centre; Stoke-on-Trent, Staffordshire UK; Haywood Rheumatology Centre; Haywood Hospital; Stoke-on-Trent, Staffordshire UK.
authors.forename: Derek L
authors.initials: DL
authors.lastname: Mattey
authors.affiliation: Institute for Science and Technology in Medicine; Keele University; Guy Hilton Research Centre; Stoke-on-Trent, Staffordshire UK.
authors.forename: William E
authors.initials: WE
authors.lastname: Farrell
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000235:genetics; D001402:B-Lymphocytes / Q000378:metabolism*; D018899:CpG Islands; D019175:DNA Methylation; D005260:Female; D015894:Genome, Human; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008875:Middle Aged; D013601:T-Lymphocytes / Q000378:metabolism*
keywords: B-lymphocyte; CpG; DNA methylation; Genome-wide; Illumina 450k array; Rheumatoid arthritis; T-lymphocyte