Department: Mechanical & Aerospace Engineering
Faculty Advisor(s): Juan Lasheras | Juan Carlos del Alamo

Primary Student
Name: Begona Alvarez-Gonzalez
Email: bealvare@ucsd.edu
Phone: 858-534-3959
Grad Year: 2014

There is still a lack of information regarding the mechanical aspects of cell migration and the quantification of the traction forces is essential to completely understand the migration process. Most of the methods developed to measure traction forces exerted by cells moving over flat substrates assume that the vertical forces exerted by the cells are negligible and they only exert tangential forces to the substrate. Now we have developed a method to determine the cellular traction forces exerted perpendicular to the substrate in addition to the in-plane forces. We measure the 3D substrate deformation by tracking the displacements of fluorescent marker beads embedded in the substrate. The traction forces exerted by the cells are obtained by solving analytically the elastostatic equation for a linearly elastic medium using the previously measured deformation of the substrate. In order to understand the role of specific cytoskeletal components in the organization of the three-dimensional stresses we are using Dictyostelium Discoideum cells, we study mutants with contractility defects and compare these mutants with Wild type cells. We are looking at Myosin II null to quantify the role that this protein plays in the mechanics of cell motility. We find that the two cell lines studied push on the substrate near the center of the cell and pull up near the periphery. The magnitude of the perpendicular forces is comparable to the magnitude of the tangential forces to the substrate; therefore this perpendicular component cannot be neglected. Our measurements indicate that the effects of mutations on the tangential and perpendicular traction forces to the substrate are different. Therefore, it suggests that the generation of the perpendicular and tangential traction forces is possibly controlled by two different mechanisms.

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