Fri. 4/6 @4pm in SCI B133

Laura Burrus, San Francisco State University, Department of Biology

During embryonic development, a single morphogen, such as Wnt, can pattern an entire field of cells. This remarkable feat is accomplished by the formation of a morphogen gradient, which then elicits concentration-dependent effects in target cells. Though we have made significant progress in understanding how upstream regulators of Wnt secretion, such as Porcupine (PORCN) and Wntless (WLS), function in the trafficking of Wnt proteins from the endoplasmic reticulum (ER) to the cell surface, far less is known about how vertebrate Wnts are transported from the site of synthesis to target cells. For many years, it was presumed that Wnt gradients were formed by the diffusion of secreted Wnt proteins away from the site of synthesis. However, the observation that Wnts are lipid modified and poorly secreted raised questions about the validity of this model. Recently, data from a number of labs, including our own, suggest a new model in which Wnts are transported to target cells via long cellular projections (eg, cytonemes, filopodia, filopodia like protrusions, and tunneling nanotubes).