Meeting Abstract
Placozoans are one of the earliest diverging metazoans with a simple body plan. They have six cell types arranged in a three-layered sheet morphology without ECM. Their extreme diversity of shape and tissue plasticity are properties arising from local interactions between cells, whose emergence can be probed due to the simplicity of the system. The animal reproduces asexually through fission induced by uncoordinated flocking of cilia, but also sometimes buds spherical pelagic swarmer balls from its dorsal surface. These balls have been reported to undergo a topological transition during which the ventral epithelium enclosing an inner cavity is exposed to the outer environment. The dorsal and ventral surfaces have characteristic functions illustrated by unique distinguishable cell arrangements. We aim to better understand the role of self-organization processes that lead to these simple tissue architectures. A shear-based dissociation assay allows us to obtain tissue fragments with tens to hundreds of cells. These fragments show motility and reaggregation followed by slow rearrangements of cells to gain defined arrangements. This process provides room for in vitro formation of swarmer balls along with other artificial morphologies with multiple cavities. The assay also allows us to obtain animals with tuned sizes which show a transition from a more rounded to a flatter morphology with increase in size. Comparative study of this process between aggregates and native animals allows us to probe the development of robust architecture in these animals using a few cell types. Our current work opens doors to building artificial animals with non-native cellular compositions, further enabling us to decipher the role of various cell types in this self-organization process.
