In contrast to FSHD cells, which sporadically express DUX4 in only a few nuclei at different times (1 in every 200 to 1000 cells [179]), MB135-DUX4i cells can be simultaneously stimulated to induce high-level expression of DUX4. This enables molecular analysis of DUX4 pathologies “under controlled and acute experimental conditions” [215]. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.