Figure 8. Working model of the pathways mediating apoptosis versus axon pruning.

Proteins highlighted in yellow have been shown to be required for both apoptosis and axon pruning pathways. Our results indicate that Apaf-1 and Caspase-6 (highlighted in blue) are two points of divergence. Future experiments will be required to determine what role, if any, is played by the mitochondria and cytc release in axon-selective degeneration. In addition, how Caspase-9 is able to activate Caspase-6 and Caspase-3 without Apaf-1 remains to be determined. While Casp6 and Casp3 are both required for axon pruning, their exact order of activation during axon pruning in neurons is still unclear.