Before a cell can do its job, it needs to get oriented. Cells must determine their purpose in life, tell their tops from their bottoms, and quite literally find their place amidst a confusing array of physical and chemical signals. Cell polarization meets these challenges. Spatial segregation assumes different roles in embryonic cells, epithelial cells, and neural precursors. And each cell type relies on a complex web of signal-transduction events to establish asymmetry.
The protein players are largely conserved across cell type and across species. Using genetic and biochemical clues, researchers are working to collect the important molecular pieces, fit them together, and figure out what they do. The research process is painstaking, but the potential payoff in understanding how such an essential cellular system is initiated cannot be overstated: Loss of polarity is a key event in epithelial cells becoming cancerous, for example, and migration of neuroglial cells determines ...
