Session Title: Genetics and Genomics of Rheumatic Diseases
Session Type: Abstract Submissions (ACR)
The importance of the epigenetic signature in RA is unclear but levels of methylation of CpG motifs in the TNF promoter are known to be important determinants of transcriptional activity. In view of the central importance of this cytokine in RA we hypothesised that methylation of the TNF gene in peripheral blood cells might differ between RA patients and controls. The primary objectives were to determine if CpG motifs in the TNF gene promoter were differentially methylated in RA compared with controls and if TNF mRNA levels correlated with DNA methylation. We also determined whether methotrexate was associated with alterations in genomic or TNF promoter DNA methylation levels.
A cross-sectional RA population (n=218) and healthy controls (n=312) was used to investigate the primary objective. A second population of RA patients starting MTX were recruited (n=33) and DNA and DAS28 scores were obtained prior to treatment and at 3 months. Methylation of seven TNF 5′ CpG motifs (-349 to -78) and LINE-1, an assay of genomic mehtylation, in peripheral blood leucocytes were assessed by pyrosequencing and levels of TNF mRNA were measured using quantitative PCR.
Levels of methylation of 4 TNF CpGs (-170, -239, -245, -304) were higher in RA compared with controls (p=7.1×10-5 to 1.3×10-10) and TNF mRNA was 58% lower in RA cases (p=1.5 x10-10). In both RA and controls negative correlations of TNF-245 methylation with TNF mRNA levels were detected (p=0.02 and 0.04 respectively). There was no difference in LINE-1 or TNF methylation in MTX treated patients and no correlation between change in methylation with DAS28 response after 3 months.
Conclusion: Higher levels of methylation of the TNF promoter are present in RA leukocytes compared with controls, and levels of TNF mRNA were lower in the patients. Methylation levels of TNF-245 were inversely correlated with TNF mRNA levels in both groups. Treatment with MTX was not associated with changes in genomic or TNF methylation levels. These results suggest that methylation of the TNF promoter is higher in RA compared with controls and that methylation of TNF-245 is an important regulatory mark for TNF expression.
J. R. Maxwell,
L. H. Taylor,
R. A. Pachecho,
G. W. Duff,
M. D. Teare,
A. G. Wilson,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/inverse-relation-between-the-tumor-necrosis-factor-promoter-methylation-and-trascript-leveles-in-leukocytes-from-patients-with-rheumatoid-arthritis/