TUNEL Staining in Sections of Paraffin-Enabled Planarians

Planarians are a model animal for the study of regeneration and homeostasis. Understanding how planarians control their cellular balance is key to the knowledge of their plasticity. Both apoptotic and mitotic rates can be quantified in “whole mount” planarians. Apoptosis is usually analyzed through terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), a technique that detects cell death by identifying DNA breaks. In this chapter we detail a protocol to analyze apoptotic cells in paraffin sections of planarians, which enables a more accurate cellular visualization and quantification than in “whole mount.”