Jessica Sawyer       2004-present     Ph.D. Student in Biology American Heart Assoc. Predoctoral Fellow

Exploring the roles of Canoe/Afadin in adhesion and cytoskeletal regulation

Cells undergo coordinated changes in shape and position during animal development. This process of morphogenesis requires cells to be able to interact with other cells and the extracellular matrix, and to be able to modulate both adhesion and the connections of cell-cell and cell-matrix junctions with the actin cytoskeleton. Adherens junctions (AJs) are the major sites of cell-cell contact in epithelial cells and this multi-protein complex also links the cytoskeleton of adjacent cells. While the key components of AJs are known, there are other proteins that are recruited AJs whose functions are less well understood. These presumed non-core AJ proteins may act redundantly to modulate junctions by regulating connections to the actin cytoskeleton or to signal transduction machinery.

Two presumed non-core AJ proteins are Canoe (Cno/AF-6) and Polycheatoid (Pyd/ZO-1). Studies of the mammalian homolog of Cno, AF-6, suggest that it plays a key role in AJs. The primary function of mammalian ZO-1 is in the tight junctions, but there is some evidence that it plays a transient role in the AJs. Both Cno and Pyd localize to the AJs in flies and have been found to genetically and physically interact. However, the role(s) of Cno and Pyd in AJs remains unclear. Cno has several putative binding partners (Ras, Rap1, Profilin, JNK pathway) and this sheds some light onto its function, but its involvement in such a large array of processes make clarifying its function a challenge. It is possible that Cno and Pyd are in fact core components of AJs and are essential for adhesion. Alternatively, Cno and Pyd may modulate adhesion by coupling it to signal transduction pathways. We will start begin analysis with Cno and will later use the same approach for Pyd. To distinguish between these two possibilities, we will first examine the consequence of removing all Cno function on embryogenesis by generating embryos that maternally and zygotically mutant for a strong allele of cno. If this experiment indicates that Cno is a core component of AJs we will examine if it is a component of the cadherin-catenin complex. However, if the phenotype is more consistent with Cno being a regulator of adhesion we will determine which processes Cno does modulate.