Matteusz: "Insights into the mechanism and evolution of glial ensheathment" Renske: "Evolution of selfish multicellularity: changes in gene regulation at the origin of multicellularity"

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• Renske Vroomans; Matteusz Trylinski
• Monday 25 October 2021, 14:30-15:30
• Online.

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Matteusz Trylinski Coordination of cellular behaviours enables both the formation of tissues and complex organs during development and the appearance of new structures during evolution. One of such events is the emergence of glial wrapping during Metazoan history, which among others increased the speed and the precision of information transfer along axons. Although we have a good understanding on the current mechanisms regulating this process, little is known about their evolutionary origin. Here, we address this question by using an evolutionary-conserved sensory organ, the Drosophila thoracic microchaete. These organs are made of four lineage-related cells – two outer structural cells and two inner sensory cells – that are organised in a concentric, or “onion-like”, fashion. Given that homologous structures can be found in Tardigrades, which have diverged from Arthropods over 500 million years ago, we speculate that the mechanisms involved in the successive ensheathments during microchaete morphogenesis might be reminiscent of the ancestral state. In particular, we investigate how, following the first lineage division that gives rise to the outer-cell and inner-cell progenitors, the future structural-sensory interface is generated, and how the inner-cell progenitor is enwrapped by the outer-cell progenitor. Our preliminary results suggest that this wrapping event combines both non-transcriptional effectors related to asymmetric cell division and transcriptional targets expressed by the inner-cell progenitor.

Renske Vroomans Most multicellular organisms undergo some form of development and morphogenesis. Recent studies have shown that many of the genetic tools to regulate these processes were already present in their unicellular ancestor. This suggests that the most ubiquitous developmental processes may also be traced back all the way to the emergence of multicellularity itself. Furthermore, the evolutionary transition to multicellularity may have predominantly required changes in regulation and coordination, more than changing the gene content. We use evolutionary models to study the evolution of cell adhesion and gene regulation at the onset of multicellularity. We find that the physical properties of cell clusters can be sufficient to drive selection for cell adhesion. Once cells evolve adhesion however, their regulatory dynamics evolve as well: while cells evolve adhesion to survive collectively, within such cohesive clusters, intercellular competition drives cells to behave “selfishly” by dividing sooner and perform the collective task later. The model demonstrates how the transition to multicellularity may have driven a drastic switch in cell behaviour, leading to complex coordinated dynamics compared to the unicellular cousins, without changing the genetic toolkit.

This talk is part of the Morphogenesis Seminar Series series.

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