Live-cell Imaging and Quantitative Analysis of Embryonic Epithelial Cells in Xenopus laevis

Summary

Xenopus embryonic epithelia are an ideal model system to study cell behaviors such as polarity development and shape change during epithelial morphogenesis. Traditional histology of fixed samples is increasingly being complemented by live-cell confocal imaging. Here we demonstrate methods to isolate frog tissues and visualize live epithelial cells and their cytoskeleton using live-cell confocal microscopy.

Abstract

Embryonic epithelial cells serve as an ideal model to study morphogenesis where multi-cellular tissues undergo changes in their geometry, such as changes in cell surface area and cell height, and where cells undergo mitosis and migrate. Furthermore, epithelial cells can also regulate morphogenetic movements in adjacent tissues¹. A traditional method to study epithelial cells and tissues involve chemical fixation and histological methods to determine cell morphology or localization of particular proteins of interest. These approaches continue to be useful and provide “snapshots” of cell shapes and tissue architecture, however, much remains to be understood about how cells acquire specific shapes, how various proteins move or localize to specific positions, and what paths cells follow toward their final differentiated fate. High resolution live imaging complements traditional methods and also allows more direct investigation into the dynamic cellular processes involved in the formation, maintenance, and morphogenesis of multicellular epithelial sheets. Here we demonstrate experimental methods from the isolation of animal cap tissues from Xenopus laevis embryos to confocal imaging of epithelial cells and simple measurement approaches that together can augment molecular and cellular studies of epithelial morphogenesis.

Protocol

Before you begin Synthesize capped mRNA from linearized DNA template encoding the fluorescently tagged protein and purify mRNA by standard methods (AmpliCap Transcription kit; Epicentre Biotechnologies, Madison WI). mRNA should be aliquoted for single time use in 0.2 ml centrifuge tubes and stored at -80°C. Standard methods to obtain eggs, in vitro fertilization, and removal of the egg coat have been described previously2. A procedure to obtain eggs from a …

Discussion

We have presented experimental protocols used regularly in our lab to image dynamically changing cytoskeleton in the apical cell cortex and oscillating cell membranes of epithelial cells in Xenopus embryos. One should use these protocols as a starting point for live-imaging of epithelial cell shapes; optimization of this protocol is essential and some of the settings will change depending on the type of microscope system one has and the type of proteins one is interested in imaging. Together, the protocol steps …