Chapter 2
Perspective on Epithelial-Mesenchymal Transitions
in Embryos
David R. McClay
Abstract
The epithelial-mesenchymal transition (EMT) is a key process required for building the early body plan of
metazoa. It involves coordinated and precisely timed changes in multiple cell processes such as de-adhesion,
motility, invasion, and cell polarity. While much has been learned about how embryos deploy epithelialmesenchymal transitions since Betty Hay named the process decades ago, a number of things are still not
well understood. Here I will discuss some of the big questions that remain, including how is all of this
controlled, how does each of the cell biological events work, and how are they so nicely coordinated with
one another?
Key words Gastrulation, Epithelial-mesenchymal transition, Morphogenesis, Sea urchin
1 Introduction
Morphogenetic movements at gastrulation reshape the embryos of
multicellular animals. Among those movements, an epithelialmesenchymal transition (EMT) removes mesoderm cells from an
epithelium and places them in between the ectoderm and endoderm. Other embryonic cell types also go through EMTs at various
stages of development in many animals. The EMT process is thus
essential for building the early body plan of metazoa, and because
of this it is important to learn how the process works at a molecular
level.
A number of properties of developmental EMTs are not well
understood. As part of the EMT, the cells become motile while still
in the epithelium. That motility results in cell shape changes, helps
the cell penetrate through the basement membrane, and mechanically contributes to the loss of adhesion as the cell leaves the
adherens junction. The invasion through the basement membrane
involves at least a partial remodeling of the basement membrane
plus a determined polarized movement of the cell. The cell
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_2,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
7
Perspective on Epithelial-Mesenchymal Transitions
in Embryos
David R. McClay
Abstract
The epithelial-mesenchymal transition (EMT) is a key process required for building the early body plan of
metazoa. It involves coordinated and precisely timed changes in multiple cell processes such as de-adhesion,
motility, invasion, and cell polarity. While much has been learned about how embryos deploy epithelialmesenchymal transitions since Betty Hay named the process decades ago, a number of things are still not
well understood. Here I will discuss some of the big questions that remain, including how is all of this
controlled, how does each of the cell biological events work, and how are they so nicely coordinated with
one another?
Key words Gastrulation, Epithelial-mesenchymal transition, Morphogenesis, Sea urchin
1 Introduction
Morphogenetic movements at gastrulation reshape the embryos of
multicellular animals. Among those movements, an epithelialmesenchymal transition (EMT) removes mesoderm cells from an
epithelium and places them in between the ectoderm and endoderm. Other embryonic cell types also go through EMTs at various
stages of development in many animals. The EMT process is thus
essential for building the early body plan of metazoa, and because
of this it is important to learn how the process works at a molecular
level.
A number of properties of developmental EMTs are not well
understood. As part of the EMT, the cells become motile while still
in the epithelium. That motility results in cell shape changes, helps
the cell penetrate through the basement membrane, and mechanically contributes to the loss of adhesion as the cell leaves the
adherens junction. The invasion through the basement membrane
involves at least a partial remodeling of the basement membrane
plus a determined polarized movement of the cell. The cell
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_2,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
7