Abstract: Series 108, Lecture 1
The Harvey Lectures Series 108 (2012—2013)
Lecture #1: Thursday, October 18, 2012 — Watch Video of Lecture
Cell Shape During Drosophila Gastrulation:
Science at the Interface of Biology, Biophysics and Aesthetics
Eric F Wieschaus, PhD
Squibb Professor in Molecular Biology
Professor of Molecular Biology and the Lewis-Sigler Institute for Integrative Genomics
Investigator, Howard Hughes Medical Institute
Howard Hughes Medical Institute, Princeton University
Princeton, New Jersey
During their development, embryos undergo extraordinary morphological transformations that convert what is initially a simple ball of uniform cells into a complex 3D structure. These transformations are remarkable for their speed and precision, but also for their incredible beauty. The cell shape changes that underlie such transformations depend on patterns of gene activity, but how such patterns are converted into the physical properties controlling shape and motility is a major unanswered question in biology. In my talk I will describe my lab’s attempts to address these questions over the past thirty years using the Drosophila embryo as a model system.
Much of our work has focused on the ventral region of the Drosophila embryo, where cells are assigned to the mesodermal cell fate by two transcription factors, Twist and Snail. These cell fate decisions are immediately followed by changes in cell shape that bring the mesoderm into the interior of the embryo. Our previous studies showed that expression of the two transcription factors induce a specialized pulsating network of actin and myosin in the apical surface of mesodermal cells, and that contraction of this network drives the subsequent changes in cell shape. Understanding how such localized cytoskeletal elements can govern global changes in cell shape has required computational tools to measure the physical properties of the cells and track how forces generated apically can be transmitted over large distances in the cytoplasm. Surprisingly, we find that the changes that occur in epithelial sheets can often be understood as global patterns of cytoplasmic flow, independent of the behaviors of individual cells. Consistent with this view, we also find that many of the morphological changes in mesodermal cells still occur in “syncytial embryos” in which the partitioning of the cytoplasm into discrete cells has been blocked by mutations. These findings open up a new perspective on the relationship between cells and organismal morphology.