UC Berkeley

How animals develop the complex structures and morphologies that result in diversification and speciation is a fundamental question in evolutionary biology that can be addressed through studies of embryogenesis. Gastrulation is an early morphogenetic event that establishes the embryonic tissue layers that will give rise to the various organs and characteristics of the adult. Cells and their interactions are the basis of this process. Outside of Drosophila melanogaster, little is known about the behavior of cells during gastrulation in arthropods.

This dissertation focuses on cell behavior during gastrulation in the amphipod crustacean Parhyale hawaiensis. Using a variety of techniques, we make novel observations about cell shape change, the autonomy of cell behavior, and investigate possible molecular regulators of the entire process. I found cell shape change in the rosette that confirms previous hypotheses suggesting that gastrulation in Parhyale proceeds through ingression or invagination. I also found that the rosette and epithelial sheet act autonomously, and that the descendants of different lineages within the rosette are able to internalize independently. Using drug inhibition, I identified rho-kinase as important to epithelial integrity during gastrulation, and discovered a phenotype that may be associated with abnormal cell division. Finally, I investigated several candidate genes in an effort to discover a molecular marker for early mesoderm and ectoderm fate. This study provides valuable information about the process of cell internalization, cell autonomy during gastrulation, and suggests potential highly conserved mechanisms for cell behavior during Parhyale gastrulation.