The degree of demethylation at D4Z4 in the FSHD LCL clones is as expected for FSHD1, and the 61 FSHD LCLs generally display robust DUX4 expression, as well as DUX4 target genes ZSCAN4, TRIM43 and MBD3L2 (42). Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.