Expression profiling of planarians shed light on a dual role of programmed cell death during the regeneration

Most animals hold the ability to regenerate damaged cells, tissues, and even any lost part of their bodies. To date, there is little known about the precise regulatory mechanism of regeneration and many fundamental questions remain unanswered. To further understand the precise regulatory mechanism of regeneration, we used planarian Dugesia japonica as a model and sequenced the transcriptomes of their regenerated tissues at different regeneration stages. Through de novo assembly and expression profiling, we found that Heat shock protein and MAPK pathway were involved into early response of regeneration in D. japonica. In addition, immune response, cell proliferation, and migration were activated during regeneration. Of notes, our results revealed a specific functional role of programmed cell death (PCD) in regeneration of D. japonica. PCD may not only remove the damaged and superfluous tissues for further patterning with regenerated tissues, but also provide signals to trigger neoblasts proliferation and differentiation directly. Together, our results revealed Heat shock protein and MAPK pathway mediated early response of regeneration and found a dual role of PCD in regeneration D. japonica. Meanwhile, we constructed regulatory networks of apoptosis, autophagy, and related signaling pathways and proposed a schematic model, which provided a global landscape of regeneration.