DUX4 and facioscapulohumeral muscular dystrophy: PMOs have also been used to target the PAS in exon 3 (Figure 3), which knocked down DUX4 transcript expression in immortalized patient-derived myotubes by 25–52% at a 50 nM dose (Marsollier et al., 2016) and in a xenograft FSHD mouse model by nearly 100% with a 20-μg injection (Chen et al., 2016a).