ASH1L and facioscapulohumeral muscular dystrophy: Other observations argue for a role for the Polycomb proteins in the epigenetic regulation at D4Z4: The methyl-transferase EZH2 (Enhancer of zeste homolog 2), a component of Polycomb repressive complex 2 (PRC2), was shown to be reduced in FSHD muscle cells, while ASH1L (ASH1 Like Histone Lysine Methyltransferase), a member of the Trithorax complex associated with transcriptionally active chromatin, was found to be specifically recruited to D4Z4 in FSHD cells [43].