Fig. 9. Schematic illustration of CNS maintenance and regeneration. In normal planarian regeneration (upper panel), blastema formation is followed by patterning and cell differentiation of neural cells, and then the neural cells are organized into neural circuits, which are maintained by homeostasis. In DjCHC-silenced planarians (lower panel), the patterning and cell differentiation of neural cells occur normally, but neurites regress and neural cells die via apoptosis, resulting in atrophy of the CNS.