S03-03. High resolution live microscopy of cell motility, actin dynamics and cell-cell contacts along embryonic tissue boundaries

The planar cell polarity (PCP) signaling pathway is essential for a wide variety of celland tissue-level morphogenetic events in developing embryos. PCP research has been predominantly directed at the role played by a small number of core proteins, including Dishevelled and Frizzled. Much less is known about how these proteins signal downstream to direct the execution of such diverse cell behaviors as convergent extension and ciliogenesis. We have focused recently on the downstream PCP effector proteins, Fuz and Fritz. We show that Fuz is essential for ciliogenesis, but plays only a minor role in convergent extension. Combining bioinformatics with confocal and electron microscopy, we establish a central role for Fuz in membrane trafficking, showing that Fuz is essential for apical trafficking of ciliogenesis factors in ciliated cells and for exocytosis in secretory cells. Unlike Fuz, Fritz plays a major role in convergent extension. Time-lapse imaging reveals a cytoskeletal role for Fritz that is essential for the maintenance plasma membrane stability and cell shape. Together, these results provide novel insights into the mechanisms by which upstream developmental regulatory systems like PCP signaling are linked to the basic cellular machinery during embryonic morphogenesis.