Chapter 3
EMT, One of Many Morphological Transitions in Cellular
Phase Space
Denise J. Montell
Abstract
The epithelial to mesenchymal transition (EMT) is an enticingly simple mechanism that converts stationary
epithelial cells into migratory mesenchymal cells. EMT is meant to provide a unified explanation for
phenomena as complex as gastrulation and metastasis. However, cell movements turn out to be diverse,
and many are collective. Cells commonly migrate in clusters, strands, sheets, elongating tubes, or in fluidlike masses. Moreover, plenty of cells move without activating the EMT program. Here I propose that EMT
can be understood as one of many types of transitions in a broader landscape—or phase space—of cell
morphologies and behaviors. Throughout biology, and at multiple scales, complexity arises from the
combinatorial deployment of simple, modular components. I propose that diversity of cell shapes and
behaviors similarly arises from combinatorial use of modular biomechanical properties.
Key words Epithelial to mesenchymal transition, Collective cell migration, Cell forces, Mechanical
properties, Cell shape and behavior
1 The Enticing EMT
Simple ideas are enticing. Take the DNA double helix. Just like
that, the simple concept of base pairing explained all kinds of
puzzling phenomena such as replication of genetic information,
built-in redundancy, and the known but perplexing perfect match
between the number of adenine and thymine bases and between
guanine and cytosine. Base pairing neatly explains it all. Or consider
action potentials. The electricity that generates our ideas, thoughts,
and feelings boils down to the mathematical simplicity of the
Nernst equation. Simple ideas that explain complex phenomena
are the pinnacle in science.
The epithelial to mesenchymal transition (EMT) is an enticingly simple idea meant to explain some of the most complex
phenomena in all of biology, like gastrulation and tumor metastasis.
This simplicity has been the source of the EMT’s popularity over
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_3,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
13
EMT, One of Many Morphological Transitions in Cellular
Phase Space
Denise J. Montell
Abstract
The epithelial to mesenchymal transition (EMT) is an enticingly simple mechanism that converts stationary
epithelial cells into migratory mesenchymal cells. EMT is meant to provide a unified explanation for
phenomena as complex as gastrulation and metastasis. However, cell movements turn out to be diverse,
and many are collective. Cells commonly migrate in clusters, strands, sheets, elongating tubes, or in fluidlike masses. Moreover, plenty of cells move without activating the EMT program. Here I propose that EMT
can be understood as one of many types of transitions in a broader landscape—or phase space—of cell
morphologies and behaviors. Throughout biology, and at multiple scales, complexity arises from the
combinatorial deployment of simple, modular components. I propose that diversity of cell shapes and
behaviors similarly arises from combinatorial use of modular biomechanical properties.
Key words Epithelial to mesenchymal transition, Collective cell migration, Cell forces, Mechanical
properties, Cell shape and behavior
1 The Enticing EMT
Simple ideas are enticing. Take the DNA double helix. Just like
that, the simple concept of base pairing explained all kinds of
puzzling phenomena such as replication of genetic information,
built-in redundancy, and the known but perplexing perfect match
between the number of adenine and thymine bases and between
guanine and cytosine. Base pairing neatly explains it all. Or consider
action potentials. The electricity that generates our ideas, thoughts,
and feelings boils down to the mathematical simplicity of the
Nernst equation. Simple ideas that explain complex phenomena
are the pinnacle in science.
The epithelial to mesenchymal transition (EMT) is an enticingly simple idea meant to explain some of the most complex
phenomena in all of biology, like gastrulation and tumor metastasis.
This simplicity has been the source of the EMT’s popularity over
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_3,
© Springer Science+Business Media, LLC, part of Springer Nature 2021
13