sequence of RNA appearance and disappearance. This along with
the known GRN has enabled us to pry much more deeply into the
workings of the EMT than we ever thought possible. Still, there are
many questions to address.
The future holds many remaining questions. Along with gaining details of the de-adhesion, motility, invasion, and cell polarity
changes, it is important to know how uniform or diverse the EMT
process is in different tissues. As morphogenesis progresses in the
sea urchin, five different cell types undergo an EMT hours apart
from one another. In time-lapse movies, those EMTs look similar
but from what little we have learned, each EMT is quite different
from the others at a molecular level. What is needed is an in-depth
analysis of many of these EMTs to learn whether in fact each EMT
is indeed unique in its molecular control, both transcriptionally and
with effector proteins, or, are there proteins that are universally and
uniquely involved in EMTs? That universality seems to be the target
of cancer EMT studies because it would provide a focal point for
attempts to inhibit that EMT that initiates metastasis. In embryos,
such a protein would also be valuable for many reasons, ranging
from evolutionary mechanisms to targeted perturbations in studies
of morphogenesis.
Another big question in morphogenesis is how the EMT is
timed and coordinated. As indicated above, five different EMTs
occur during gastrulation. Each starts at a fairly precise time, and
each is coordinated such that all the cell biological changes of that
EMT occur harmoniously. An ability to follow events in single cells
as outlined above will help uncover these mechanisms. From the
time-lapse movies of the process it appears as though there are a
number of possibilities for mechanical sensing, and if that is the case
there will be opportunities for gaining an understanding of how
such sensing relays information to other components of the EMT.
Even though the remaining questions are quite numerous,
much has been learned about how embryos deploy epithelialmesenchymal transitions since Betty Hay named the process decades ago. Since then progress has paralleled advances in molecular
technologies. With many new technologies being introduced at a
rapid pace, the next decade should be rich with discoveries about
how EMTs work in embryos.
Acknowledgments
Thanks to the many students and postdocs in the McClay lab who
contributed so much over the years to advance our understanding
of the EMT. Thanks also to the NIH for supporting this work: RO1
HD14483 (to DRM) and PO1 HD 37105 (Project 2 to DRM).
Perspective on Epithelial-Mesenchymal Transitions in Embryos
11
the known GRN has enabled us to pry much more deeply into the
workings of the EMT than we ever thought possible. Still, there are
many questions to address.
The future holds many remaining questions. Along with gaining details of the de-adhesion, motility, invasion, and cell polarity
changes, it is important to know how uniform or diverse the EMT
process is in different tissues. As morphogenesis progresses in the
sea urchin, five different cell types undergo an EMT hours apart
from one another. In time-lapse movies, those EMTs look similar
but from what little we have learned, each EMT is quite different
from the others at a molecular level. What is needed is an in-depth
analysis of many of these EMTs to learn whether in fact each EMT
is indeed unique in its molecular control, both transcriptionally and
with effector proteins, or, are there proteins that are universally and
uniquely involved in EMTs? That universality seems to be the target
of cancer EMT studies because it would provide a focal point for
attempts to inhibit that EMT that initiates metastasis. In embryos,
such a protein would also be valuable for many reasons, ranging
from evolutionary mechanisms to targeted perturbations in studies
of morphogenesis.
Another big question in morphogenesis is how the EMT is
timed and coordinated. As indicated above, five different EMTs
occur during gastrulation. Each starts at a fairly precise time, and
each is coordinated such that all the cell biological changes of that
EMT occur harmoniously. An ability to follow events in single cells
as outlined above will help uncover these mechanisms. From the
time-lapse movies of the process it appears as though there are a
number of possibilities for mechanical sensing, and if that is the case
there will be opportunities for gaining an understanding of how
such sensing relays information to other components of the EMT.
Even though the remaining questions are quite numerous,
much has been learned about how embryos deploy epithelialmesenchymal transitions since Betty Hay named the process decades ago. Since then progress has paralleled advances in molecular
technologies. With many new technologies being introduced at a
rapid pace, the next decade should be rich with discoveries about
how EMTs work in embryos.
Acknowledgments
Thanks to the many students and postdocs in the McClay lab who
contributed so much over the years to advance our understanding
of the EMT. Thanks also to the NIH for supporting this work: RO1
HD14483 (to DRM) and PO1 HD 37105 (Project 2 to DRM).
Perspective on Epithelial-Mesenchymal Transitions in Embryos
11