In gastrocnemius muscle of D4Z4-2.5 mice, the D4Z4 units were relatively hypomethylated (10–20%; p<3.10−5) (Figure 5C), similar to FSHD patients and in concordance with the observed difference in DUX4 expression between the two mouse lines (Figure 3A). This evidence concerns the gene DUX4 and Facioscapulohumeral dystrophy.