MYOD1 and facioscapulohumeral muscular dystrophy: We transduced human MB135 control (non-FSHD) myoblasts with a lentiviral vector co-expressing FLAG-tagged, nuclease-deficient Cas9 (FLAG-dCas9) and guide RNA (gRNA) targeting the 3’ end (gD4Z4-1), middle (gD4Z4-2) or 5’ end (gD4Z4-3) of the D4Z4 unit, or the MYOD1 distal regulatory region (DRR) (gMYOD1) for comparison.