Matthias Pechmann
University of Cologne, Cologne Biocenter, Institute of Zoology
Germany
How to "organize" a spider embryo. Insights into early spider embryogenesis and beyond.
The establishment of the anteroposterior (AP) and dorsoventral (DV) body axes is a crucial process during the early embryonic development of bilaterally symmetric animals. In many animals, ‘organizers’ are key players to induce the main body axes and to induce gastrulation and germ layer patterning. In spiders, the organizer is known as the ‘cumulus’. The spider cumulus, a cluster of migratory and signalling cells, is formed during early embryogenesis and induces the formation of the dorsoventral (DV) body axis via the activation of the BMP signalling pathway in cumulus adjacent cells. In close association to this process, cumulus migration is crucial to induce dorsal cell fate at the correct position within the embryo. Previous studies indicate that Hedgehog- as well as FGFR-signalling is involved in cumulus migration. Overall, the proper formation and migration of cumulus cells is key to normal spider embryogenesis. While the loss of the cumulus is blocking DV axis formation, duplication of the cumulus can induce embryonic twinning.
Many aspects of the organizing capacities of the spider cumulus are still poorly understood. Especially the gene regulatory networks that are associated with cumulus migration, cumulus cell cohesion and signalling are crucial to understand axes formation in spiders. Our analyses focus on these cumulus specific gene regulatory networks (GNRs) and provide a better understanding of the mechanisms that lead to proper axes formation in spiders and other chelicerate species.
Taller or smaller: How feeding controls body plasticity in a sea anemone?
Most animals regulate their growth rates and body sizes to match the amount of nutrients available in the environment. Although this capacity constitutes one of the oldest physiological control processes in animals, it is only poorly understood on a cellular and molecular level.
I will present our current cellular and molecular understanding of how changes in nutrient supply affect body size and growth rates in the sea anemone Nematostella vectensis. On a whole-body level, we found that feeding drives body growth by cell proliferation while starvation leads to whole-body shrinkage and massive cell loss. I will show how food supply affects cell cycle progression, TOR signalling activity and apoptosis levels on a whole-body level and in a specific population of multipotent stem-like cells. In addition, we observed that epithelial cell extrusion occurs during starvation-induced cell loss and is likely evolutionary conserved between cnidarians and bilaterians.
Altogether, our research forms the foundation to start understanding how cell physiology integrates nutritional input to control cell cycle progression and body plasticity in animals with lifelong growth.
