Chromatin characterization of FRG1 and the D4Z4 array in FSHD myoblasts revealed a reduction in H3K27me3 on the contracted D4Z4 allele, and a kinetic analysis of Polycomb dissociation during differentiation that was very similar to that observed in the control cells. This evidence concerns the gene FRG1 and Facioscapulohumeral dystrophy.