Who does the hair cell's 'do? Rho GTPases and hair-bundle morphogenesis

The mechanosensitive hair bundles of vertebrate hair cells exhibit a remark able variety of shapes, For a given location in a sensory epithelium, howev er, the shape and polarity of a hair bundle are specified precisely. Recent findings, in particular with analogous experimental systems of actin polym erization, suggest a model of hair-bundle morphogenesis whereby different R ho guanosine triphosphatases (GTPases) regulate the initiation phase and th e elongation phase of local actin-filament assembly at the hair cell's apic al membrane.