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The epithelium is one of the best studied tissues for morphogenesis, pattern formation, cell polarity, cell division, cell competition, tumorigenesis, and metastatic behaviors. However, it has been challenging to analyze real-time cell interactions or cell dynamics within the epithelia under physiological conditions. The Drosophila pupal abdominal epidermis is a model system that allows to combine long-term real-time imaging under physiological conditions with the use of powerful Drosophila genetics tools. The abdominal epidermis displays a wide range of stereotypical characteristics of the epithelia and cellular behaviors including cell division, cell death, cell rearrangement, apical constriction, and apicobasal/planar polarity, making this tissue a first choice for the study of epithelial morphogenesis and relevant phenomena. In this chapter, I describe the staging and mounting of pupae and the live imaging of the abdominal epidermis. Moreover, methods to combine live imaging with mosaic analysis or drug injection will be presented. The long-term live imaging of the pupal abdominal epidermis is straightforward and opens up the possibility to analyze cell dynamics during epithelial morphogenesis at an unprecedented resolution.

Epithelia are tissues that regulate exchanges with the environment. They are very dynamic and can acquire virtually any shape; at the cellular level, they are composed of cells tightly connected by junctions. Most often epithelia are amenable to live imaging; however, the large number of cells composing an epithelium and the absence of informatics tools dedicated to epithelial analysis largely prevented tissue scale studies. Here we present Tissue Analyzer, a free tool that can be used to segment and analyze epithelial cells and monitor tissue dynamics.