ERG and acute lymphoblastic leukemia: In DUX4-r B-ALL, repeat units from the D4Z4 or 10q26 loci are typically inserted out-of-frame into the immunoglobulin heavy locus (IGH) or – more rarely - the ETS-related gene (ERG) [3, 52], though a wide range of other gene partners have been identified in around 4.6% of DUX4-r cases (Fig. 4).