During healthy myogenic differentiation, the up-regulation of KLF15 (shown as overexpressed in FSHD muscle cells and biopsies) induces DUX4c, following its binding to and activation of the D4Z4 enhancer that comes in direct contact with the DUX4c promoter in healthy and FSHD myoblasts [69, 70]. Here, DUX4L9 is linked to facioscapulohumeral muscular dystrophy.