Role of DNA methylation on human CTSG in dermatomyositic myoideum

Dermatomyositis (DM) is a multifactorial chronic autoimmune disorder with characteristic skin and muscle pathological changes and involvement of other organ systems. Cathepsin G (CTSG) contributes to the risk of developing DM, which is likely to be associated with inflammatory cytokines. Differential DNA methylation on CTSG has been determined to be implicated in DM in vivo. However, the underlying mechanism of this epigenetic regulation on CTST in DM is poorly explored. In this study, we investigated DNA methylation signature on CTSG at single-nucleotide resolution in quadriceps femoris of six DM patients and paracancerous muscles of three patients with rhabdomyosarcoma on inner thigh using pyrosequencing, and observed that the overall DNA methylation level of CTSG was increased in DM compared to control, in which CpG loci at third and fourth exons but not promoter contributed to the significantly hypermethylation. Furthermore, we observed that transcription and DNA methylation of CTSG were both declined in DNMT3a knockdown compared to DNMT1 and DNMT3b knockdown in human skeletal muscle SJCRH30 and A-204 cell lines exposed to TNF-α. Furthermore, Bortezomib (NF-κB inhibitor) and Brevilin A (JAK/STAT inhibitor) were employed to treat SJCRH30 and A-204 cells respectively, and we observed that CTSG was hypomethylated and silenced after Bortezomib treatment compared to untreatment and Brevilin A. Finally, ChIP-qPCR indicated that DNMT3a could bind to the coding regions of CTSG and the interaction was dependent on NF-κB activity. Taken together, our results determined a novel regulatory mechanism of DNA methylation on CTSG in DM. This article is protected by copyright. All rights reserved.

Keywords: CTSG; DNA methylation; Dermatomyositic; NF-κB signaling pathway.