Cell Proliferation Analysis during Xenopus Metamorphosis: Using 5-Ethynyl-2-Deoxyuridine (EdU) to Stain Proliferating Intestinal Cells

Proper cell proliferation is important for organ homeostasis and normal tissue development. Aberrations in cell proliferation, however, can give rise to degenerative diseases and cancer. Therefore, accurate and simple methods to evaluate cell proliferation are important and necessary to understand the pathways regulating cell proliferation and mechanisms underlying normal development and pathogenesis. The thymidine analog 5-ethynyl-2′-deoxyuridine (EdU), which is incorporated into DNA during active DNA synthesis (e.g., during S phase of the cell cycle), allows easy visualization of proliferating cells. Incorporated EdU can be detected without harsh chemical or enzymatic treatments and is fully compatible with a number of other staining methods, such as immunohistochemistry and in situ hybridization. This protocol describes how to detect proliferating cells using EdU staining in the intestines of Xenopus tadpoles (stages 54–66). Although this method was developed for studying intestinal metamorphosis, it should be applicable to other tissues/organs and other developmental stages as well.