αTub84B regulatory sequences drive expression of the 'Apomut' fusion protein, which is comprised of two fluorescent proteins (mRFP1 and EGFP) separated by sequence derived from the Diap1 gene. The Diap1 sequence corresponds to amino acids 1-146 in which the DQVDNN caspase cleavage site has been mutated to DQVANN, so that it can no longer be cleaved. In addition, a transmembrane domain (Tag:M(mCd8a)) is fused to the N-terminal end of the mRFP1 sequence and a nuclear localization signal (Tag:NLS(SV40-largeT)) is fused to the N-terminal end of the EGFP sequence. Due to the cleavage site mutation, the transmembrane domain tethers both fluorescent proteins to the membrane regardless of caspase activity, and thus 'Apomut' is intended as a control for the 'Apoliner' caspase sensor.