UASt regulatory sequences drive expression of the 'Casor' sensor, designed to allow caspase activity to be detected in vivo via a change in subcellular location of a fluorescent signal. The sensor is a fusion protein that consists of a Tag:M(mCd8a) membrane-targeting sequence, a 40 amino acid residue portion of Hsap\PARP1 which contains a caspase cleavage site, the EGFP fluorescent protein and a Tag:NLS(tra) nuclear localization signal. The design means that in the absence of caspase activity, the sensor is expected to be tethered to the plasma membrane due to the presence of the Tag:M(mCd8a) sequence, while in cells which contain an active caspase, cleavage within the Hsap\PARP1 sequence should release the Tag:NLS(tra)-tagged EGFP fragment, which can then enter the nucleus. Casor is a reliable sensor of apoptosis when expressed in neuronal cell types, with the change in subcellular location occurring as expected, but in non-neuronal cell types, cytoplasmic aggregates are formed, preventing its use as a caspase sensor in these cell types.