Wnt Signaling

Wnt signaling refers to a major form of communication between nearby cells. It can be conceptually divided into two main branches or biochemical pathways.

Wnt/b-catenin pathway: regulates levels of b-catenin, a protein that controls gene expression (i.e. whether a gene is "on" or "off") inside the cell nucleus. This pathway helps determine crucial biological decisions such as how many times an immature cell divides, when it stops dividing, and what kind of mature cell it becomes.

b-catenin-independent Wnt pathway: by definition this is any Wnt pathway that does not regulate b-catenin levels. Multiple b-catenin-independent pathways have been described in different cell types. One common ouput of these pathways is cytoskeletal dynamics, which controls cell shapes and movements. Perhaps the best defined b-catenin-independent pathway is the:

Planar Cell Polarity (PCP) pathway, which determines the transverse orientation of cells in many epithelial tissues. The PCP pathway also regulates some types of cell migration during development.

Each of these biochemical pathways interacts with protein structures located on the plasma membrane that help determine adhesive properties between neighboring cells, such as the cadherin/catenin complex (partly composed of the b-catenin protein in a structural role). Relationships between these pathways are a focus of investigation in many laboratories.