MECP2 and rheumatoid arthritis: Recently, by using loss and gain of function experiments in vitro, Miao et al. identified that the methyl-CpG-binding protein (MeCP2) had a function on regulation frizzled-related protein 4 (SFRP4) expression in RA through a mechanism of epigenetic modification of SFRP4 gene, which could be used as a diagnostic marker and prognostic indicators of RA [34, 35].