Chapter 8
Live Imaging of Epithelial-Mesenchymal Transition
in Mesoderm Cells of Gastrulating Drosophila Embryos
Lingkun Gu and Mo Weng
Abstract
Epithelial-mesenchymal transitions (EMTs) drive the generation of cell diversity during both evolution and
development. More and more evidence has pointed to a model where EMT is not a binary switch but a
reversible process that can be stabilized at intermediate states. Despite our vast knowledge on the signaling
pathways that trigger EMT, we know very little about how EMT happens in a step-wise manner. Live
imaging of cells that are undergoing EMT in intact, living, animals will provide us valuable insights into how
EMT is executed at both the cellular and molecular levels and help us identify and understand the
intermediate states. Here, we describe how to image early stages of EMT in the mesoderm cells of live
Drosophila melanogaster embryos and how to image contractile myosin that suspends EMT progression.
Key words Live imaging, Drosophila embryo, Epithelial-mesenchymal transition, Adherens junctions, Myosin
1 Introduction
The epithelial-mesenchymal transition (EMT) is a process where
highly organized epithelial cells lose cell polarity and junctions and
leave epithelial sheets to become migratory mesenchymal cells. The
emergence of EMT allowed the evolution from animals with epithelial cells only, to animals with diverse tissue types [1]. Accordingly, during embryogenesis, the first EMT occurs upon
gastrulation to generate three germ layers, which lay out the foundations of different tissues [1]. Despite EMT being first discovered
in development, it has also been found to play a central role during
tumorigenesis [2, 3]. Recent advances in EMT studies suggest that
cells that activate EMT programs often only progress partially along
the epithelial-mesenchymal axis, expressing a mixture of epithelial
and mesenchymal markers. In addition, EMT can be followed by its
reverse process MET, such as in the case of endoderm development,
epithelial wound healing, and tumor metastasis. The concept of
Kyra Campbell and Eric Theveneau (eds.), The Epithelial-to Mesenchymal Transition: Methods and Protocols,
Methods in Molecular Biology, vol. 2179, https://doi.org/10.1007/978-1-0716-0779-4_8,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
65
Live Imaging of Epithelial-Mesenchymal Transition
in Mesoderm Cells of Gastrulating Drosophila Embryos
Lingkun Gu and Mo Weng
Abstract
Epithelial-mesenchymal transitions (EMTs) drive the generation of cell diversity during both evolution and
development. More and more evidence has pointed to a model where EMT is not a binary switch but a
reversible process that can be stabilized at intermediate states. Despite our vast knowledge on the signaling
pathways that trigger EMT, we know very little about how EMT happens in a step-wise manner. Live
imaging of cells that are undergoing EMT in intact, living, animals will provide us valuable insights into how
EMT is executed at both the cellular and molecular levels and help us identify and understand the
intermediate states. Here, we describe how to image early stages of EMT in the mesoderm cells of live
Drosophila melanogaster embryos and how to image contractile myosin that suspends EMT progression.
Key words Live imaging, Drosophila embryo, Epithelial-mesenchymal transition, Adherens junctions, Myosin
1 Introduction
The epithelial-mesenchymal transition (EMT) is a process where
highly organized epithelial cells lose cell polarity and junctions and
leave epithelial sheets to become migratory mesenchymal cells. The
emergence of EMT allowed the evolution from animals with epithelial cells only, to animals with diverse tissue types [1]. Accordingly, during embryogenesis, the first EMT occurs upon
gastrulation to generate three germ layers, which lay out the foundations of different tissues [1]. Despite EMT being first discovered
in development, it has also been found to play a central role during
tumorigenesis [2, 3]. Recent advances in EMT studies suggest that
cells that activate EMT programs often only progress partially along
the epithelial-mesenchymal axis, expressing a mixture of epithelial
and mesenchymal markers. In addition, EMT can be followed by its
reverse process MET, such as in the case of endoderm development,
epithelial wound healing, and tumor metastasis. The concept of
Kyra Campbell and Eric Theveneau (eds.), The Epithelial-to Mesenchymal Transition: Methods and Protocols,
Methods in Molecular Biology, vol. 2179, https://doi.org/10.1007/978-1-0716-0779-4_8,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
65