Meeting Abstract
A fundamental requirement for multicellularity is cell adhesion. This includes mechanisms by which cells adhere to each other, and to their secreted extracellular matrix (ECM). Two well characterized adhesion complexes in animals include: 1) adherens junctions (AJs), which are involved in cell-cell adhesion and minimally composed of cadherin receptors, p120-, α and β-catenin, and 2) focal adhesions (FAs), which are involved in cell-ECM adhesion and include proteins such as integrins, vinculin, paxillin, talin and focal adhesion kinase (FAK). Dynamic regulation of AJs is critical for developmental morphogenesis and tissue homeostasis, whereas FAs are dynamically regulated in single- and collective cell migration. The molecular components of AJs are widely conserved in animals, and largely absent in non-animals. In contrast, the molecular components of FAs have more ancient origins and can be traced to animal outgroups, and beyond. From an experimental perspective, much less is known about how AJ and FA components function and are regulated in non-bilaterian animals. A recent study of the AJ protein β-catenin in the sponge Ephydatia muelleri found that it localizes to AJ like structures at cell-cell contacts, but also to FA-like structures at the cell-ECM interface. This led us to further examine the localization patterns of the focal-adhesion proteins, vinculin and FAK in sponge tissues. Surprisingly, we find evidence that these canonical FA-components co-localize with β-catenin at both cell-cell and cell-ECM contacts, suggesting fundamental differences between the organization and molecular composition of cell junctions in tissues of sponge compared to bilaterians. Additionally, we pharmacologically perturb FAK function in vivo to test for disrupted cell adhesion and cell migration phenotypes.
