Increased DOT1L in synovial biopsies of patients with OA and RA

Abstract

The studies aimed to determine the changes of histone methylation in synovial tissues of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Synovial tissues were obtained from 30 patients including 12 OA, 16 RA, and 2 trauma that were used as control. A histone methyltransferase DOT1L of the tissues was examined for transcript level with quantitative RT-PCR and protein expression with western blot. Methylation status of DOT1L substrate, H3K79, was examined with immunohistochemistry and western blot. Two-tailed non-pair T test and chi-square test were applied for age/disease duration and gender distribution, respectively. Kruskal-Wallis test and Post hoc Dunn's test were used for examine the difference between control, OA and RA. Both transcript and protein levels of DOT1L appeared the highest in synovial tissues of RA patients and increased in that of OA patients compared to the controls with ratios of 13.8/4.7/1 and 15.5/11.2/1.0 for RA/OA/control, respectively. The changes between RA and control, and RA and OA patients were statistically significant. Both immunohistochemistry study and western blot showed an increased methylation of H3K79 in synovial tissues of OA and RA patients. Gene and protein expression of DOT1L was increased in synovial tissues of both OA and RA patients. A high level of di-methylated H3K79 was also observed in the patients. Considering the important functions of DOT1L and H3K79 contributing to the initiation and maintenance of active transcription in the genome, these unprecedented findings, although still unclear how to impact diseases, may provide novel insights to further explore pathological mechanism of OA and RA.

Pathogenesis of Osteoarthritis: Risk Factors, Regulatory Pathways in Chondrocytes, and Experimental Models

“…In addition to affecting cartilage, DOT1L seems to have an influence on synovial membrane as well. Synovial tissues of OA and RA patients show increased expression of DOT1L at both transcriptional and translational levels, along with the demethylation of its downstream H3K79 target [141]. Given its demonstrated association with OA, epigenetics-based strategies targeting the DOT1L network could be a novel therapeutic option for OA treatment; however, epigenetic modifications are regulated in an extremely complex network and other roles of DOT1L and its targeted genes are largely unknown.…”

Epigenetic Regulation in the Pathogenesis of Rheumatoid Arthritis

“…In previous studies, high transcript and protein levels of DOT1L were detected in the synovial tissues of RA patients. The results of immunohistochemistry and western blotting proved a 13.8-fold or 15.5-fold increase in methylation of H3K79 in synovial tissue of RA patients, respectively ( 33 ). The role of DOT1L and H3K79 in initiating and maintaining gnomically active transcription important functions, indirectly demonstrating that histone modifications contribute to the pathogenesis of RA.…”

Epigenetic Regulation in Knee Osteoarthritis

“…Similar to histone acetylation, changes in histone methylation are frequently related to altered gene expression and signaling pathways in chondrocytes. For instance, H3k79 methylation was reduced in OA and RA patients (He et al, 2017), while H3K9 methylation was decreased in the temporomandibular joints of elderly mice (Ukita et al, 2020). DOT1L, an enzyme involved in histone methylation of Lys79 of H3 (H3K79), was a cartilage homeostasis regulator (Monteagudo et al, 2017).…”