PRC1 and Miyoshi myopathy: Global increases in the number of bivalent and H3K27me3‐modified genes in patient‐derived MM cells correlated with advanced stages of disease and poor survival.29 Polycomb‐group proteins are a family of transcriptional repressor proteins, which regulate the deposition and maintenance of H3K27me3 repressed chromatin domains that play roles in MM tumorigenesis.30 The two major polycomb repressive complexes are PRC1 and PRC2.