Apoptosis plays an important role in many cellular processes. Dio-1 (Death Inducer-O bliterator-1), a putative transcription factor, has been indicated to function in the onset of apoptosis. Dio-1 expression is upregulated when an apoptosis is detected. It translocates to the nucleus, and activates apoptosis during limb development. Dio-1 expression can be suppressed by caspase inhibitors and Bcl-2 expression.