The predominant DUX4 transcript found in gastrocnemius and tibialis anterior muscles was the predicted 1.4 kb product for DUX4-fl that retains intron 1, with a minor 1.2 kb product in which intron 1 was spliced out, as is the case in FSHD muscle cells [5, 6, 45]. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.