The cadherin-catenin complex is necessary for cell adhesion and embryogenesis in Nematostella vectensis.

The cadherin-catenin complex is a conserved, calcium-dependent cell-cell adhesion module that is necessary for normal development and the maintenance of tissue integrity in bilaterian animals. Despite longstanding evidence of a deep ancestry of calcium-dependent cell adhesion in animals, the requirement of the cadherin-catenin complex to coordinate cell-cell adhesion has not been tested directly in a non-bilaterian organism. Here, we provide the first analysis of classical cadherins and catenins in the Starlet Sea Anemone, Nematostella vectensis. Gene expression, protein localization, siRNA-mediated knockdown of α-catenin, and calcium-dependent cell aggregation assays provide evidence that a bonafide cadherin-catenin complex is present in the early embryo, and that α-catenin is required for normal embryonic development and the formation of cell-cell adhesions between cells dissociated from whole embryos. Together these results support the hypothesis that the cadherin-catenin complex was likely a complete and functional cell-cell adhesion module in the last common cnidarian-bilaterian ancestor. SUMMARY STATEMENT: Embryonic manipulations and ex vivo adhesion assays in the sea anemone, Nematostella vectensis, indicate that the necessity of the cadherin-catenin complex for mediating cell-cell adhesion is deeply conserved in animal evolution.

Cilium structure, assembly, and disassembly regulated by the cytoskeleton.

The cilium, once considered a vestigial structure, is a conserved, microtubule-based organelle critical for transducing extracellular chemical and mechanical signals that control cell polarity, differentiation, and proliferation. The cilium undergoes cycles of assembly and disassembly that are controlled by complex inter-relationships with the cytoskeleton. Microtubules form the core of the cilium, the axoneme, and are regulated by post-translational modifications, associated proteins, and microtubule dynamics. Although actin and septin cytoskeletons are not major components of the axoneme, they also regulate cilium organization and assembly state. Here, we discuss recent advances on how these different cytoskeletal systems- affect cilium function, structure, and organization.

Intercellular adhesion in morphogenesis: molecular and biophysical considerations.

A major challenge in developmental biology is to understand how cellular processes that result from expression of the genetic program determine the material properties and shape transformations of tissues during morphogenesis. Cell/cell adhesion is critical in development, and it controls many aspects of tissue rearrangements that support morphogenesis. Intercellular adhesion not only allows cells to adhere together but also supports structure and function compartmentalization on the scale of cell assemblies, tissues, and organs. In metazoans, cadherins comprise a major class of cell/cell adhesion proteins. They form Ca(2+)-dependent, homophilic adhesive contacts between neighboring cells that results in remodeling of the underlying cortical cytoskeleton with consequential changes in mechanical properties of cells. During development, programmed cues modulate cadherin levels and subtype expression, and downstream signaling to the cortical cytoskeleton resulting in a wide continuum of adhesive properties. A quantitative output from cell/cell adhesion is intercellular adhesion energy, which as a critical determinant of cell shape and position within the tissue, and tissue shape and position in the organism. We discuss molecular mechanisms underlying intercellular adhesion energy and its role in tissue morphogenesis.