The intronic anterobithorax regulatory region sequence that is deleted in TI{TI}Ubx4kb-abx.RMCE has been re-inserted (by replacing the RMCE cassette). The inserted abx sequence is mutated: a set of low affinity Ubx-exd protein binding sites in the abxF sub-fragment of the abxFAIRE region has been mutated to abrogate binding.