In many animals, the asymmetries that underlie the specification of the body axes are established in the fertilized egg. For example, in frog and ascidian eggs, fertilization triggers massive cytoskeletal-dependent reorganizations of the cytosol to asymmetrically pattern developmental determinants along the prospective body axes. Thus, to understand axis specification, we must elucidate how cytoskeletal forces are organized in space and time and how eggs harness these forces to establish polarity.
Despite its critical role in determining cell fate, remarkably little is known about the mechanisms that orchestrate cytoplasmic reorganization and the distribution of maternal factors in ascidians. The overall aim of this proposal was to elucidate the molecular, cellular, and biophysical processes that drive cytoplasmic reorganization and how cytoplasmic reorganization determines the localization of maternal factors that pattern the developing embryo.
This project employed high-resolution microscopy, force and cell shape manipulations, and proximity biotinylation to address the following fundamental questions:
1) What are the microtubule-dependent mechanisms that regulate cytoplasmic reorganization
and anterior-posterior polarity in the ascidian egg?
2) How does cytoplasmic reorganization control the precise positioning of developmental determinants?
This study will shed light on the principles underlying anterior-posterior body axis specification and embryo patterning in ascidians and deepen our understanding of how embryogenesis is conserved among chordates.