An important properly of all cells is their ability to sense and respond to their environment. Mounting the appropriate response to an environmental challenge often involves large-scale changes in cell morphology. For example, environmental cues such as hormones or growth factors can lead to cell differentiation, proliferation, or migration. Key components of the cytoskeleton that mediate these responses are the actomyosin and microtubule systems. Nearly all aspects of cytoskeletal dynamics are tightly regulated by a network of signaling proteins that include the Rho family of small GTPases. These proteins play central roles in regulating the actin cortex, the tilamentous, actin-based meshwork that lies adjacent to the cell membrane.

As a model system for investigating cytoskeletal dynamics, we focus on the morphological oscillations that occur during cell spreading. This experimental system provides a novel window into the interactions between microtubule and filamentous actomyosin subsystems of the cytoskeleton. Modem light microscopy affords the unprecedented capability to visualize the dynamic location of cytoskeletal proteins and the activities of signaling molecules that are postulated to be important for the oscillatory phenotype(see movies below). To understand the self-emergent properties of the cytoskeletal system that give rise to this complex behavior requires the aid of mathematical modeling and computational simulations. Therefore, our goal is to develop a quantitative biophysical model that provides a mechanistic understanding of the observed oscillations. In addition to providing insight into a dynamic cytoskeletal system, our research provides a prototype for achieving a quantitative understanding of the mechanochemical coupling that underlie many cellular behaviors. Moreover, because many disorders, including cancer, involve a dysregulation of the cytoskeleton, a mechanistic understanding of this system may suggest novel therapeutic strategies for treating disease.

PUBLICATIONS   HOME

Differential Interference Contrast (DIC) timelapse (grayscale) at 40x magnification of an oscillating Swiss 3T3 cell. In red is histone-mCherry which identifies the nucleus. This timelapse was taken 25 minutes after plating and is 100x real time.

The Lifeact-RFP protein was imaged in an oscillating Swiss 3T3 cell on polystyrene using an upright confocal microscope. Lifeact-RFP binds to filamentous actin. In these rounded, oscillating cells, one can see the lifeact bound to cortical actin. The distribution of the cortical actin is polarized dynamically during oscillations. This timelapse was taken 25 minutes after plating and is 100x real time.

The RBD-3xGFP protein was imaged in an oscillating Swiss 3T3 cell on polystyrene using an upright confocal microscope. RBD-3xGFP binds to RhoA-GTP (active RhoA). In these rounded, oscillating cells, one can see RBD-3xGFP at the cell periphery, co-localizing with the cell cortex. This timelapse was taken 25 minutes after plating and is 100x real time.