Epigenome Association Study for DNA Methylation Biomarkers in Buccal and Monocyte Cells for Female Rheumatoid Arthritis

This study used buccal cells and purified blood monocytes from two different clinical cohorts involving Caucasian or African American female populations with or without arthritis. The differential DNA methylation regions (DMRs) between the control and RA populations were identified using MeDIP-seq. The DMRs (i.e., epimutations) identified in the buccal cells and monocytes were found to be distinct. The DMR associated genes were identified and many have previously been shown to be associated with arthritis. Observations indicate DMRs are cell type specific. Overall design: Buccal and monocyte samples from females of similar age were collected for comparison of individuals with and without rheumatoid arthritis. White Caucasian non-Hispanic female samples were obtained by the Arthritis Northwest (ANW) Clinic in Spokane, Washington. The African American (AA) female samples were obtained by Dx Biosamples, LLC in San Diego, California, with sample collections in the Los Angeles California area. An MeDIP-seq procedure was used to detect methylation and differential DNA methylation sites between control and arthritis sample groups were identified. These DMRs were then compared and annotated. Four seperate comparisons were made. The Caucasian (CC) buccal cell control without RA (n=13) and with RA (n=13) were compared. The Caucasian monocyte cell control without RA (n=13) and with RA (n=13) were compared. The African American (AA) buccal cell control without RA (n=9) and with RA (n=13) were compared. A combination of Caucasian and African American samples without (n=23) and with RA (n=26) were compared.