APBA1 and Friedreich ataxia: Comparison of CTCF occupancy at the MYC locus, and at another CTCF binding site at the APBA1 (Amyloid beta A4 precursor protein-binding family A member 1) locus on chromosome 9q, in FRDA versus normal cell lines did not show a similar reduction, indicating that FRDA cells do not have a generalized defect of CTCF binding (Fig. S1).