Raimon Sunyer, Vito Conte, Jorge Escribano, Alberto Elosegui-Artola, Anna Labernadie, Léo Valon, Daniel Navajas, José
Manuel García-Aznar, José J. Muñoz, Pere Roca-Cusachs and
Xavier Trepat (September 8, 2016) Science 353 (6304), 1157-1161. [doi: 10.1126/science.aaf7119]
Summary & Highlights
- Ability of cell to follow ECM stiffness = durotaxis
- “Here, we found multicellular clusters that exhibited durotaxis even if isolated constituent cells did not.”
- Applied to several epithelial cell types, required myosin motors, originated from supracellular transmission of contractile physical forces
- Using PDMS stencil, micropattern rectangular clusters of human mammary epithelial cells on fibronectin-coated polyacrylamide gels with uniform gradient or stiffness gradient > more migration to the stiff edge… MCF10A, MDCK, human epidermoid carcinoma spheroids
- Single cells did not durotax, but faster random velocity on stiffer gels
- “this feature could explain collective durotaxis because volume exclusion would force cells to move persistently away from the cluster at a higher speed on the stiffer edge.”
- To test this, knock down cell-cell junction
- Cell-cell adhesions are required for collective cell durotaxis
- Not based on local stiffness sensing, point to a long-range mechanism involving cell-cell adhesion
- Does long-range mechanism involve transmission of physical forces across the cluster?
- Use TFM
- Highest tractions localized @ edges and pointed toward the midline of the cluster; lower tractions in bulk showed no particular orientation
- Use monolayer stress microscopy
- interecellular tension (normal component of stress tensor in direction of expansion) increased up to a plateau within the first few cells at the monolayer edges
- monolayer expands by generating contractile traction forces of equal magnitude at both edges, forces transmitted across the cluster
- Uniform Stiffness: symmetric expansion, actin polymerization exceeds acto-myosin contraction to same extent at both edges
- Gradient Stiffness: substrate deforms and opposes polymerization more on the soft edge, tilting monolayer expansion toward stiff edge
- Reduced stiffness gradient = less durotaxis
- Impair long-range force transmission by knocking down alpha-catenin and laser-ablating clusters in the direction parallel to the midline
- What if instead of a gradient stiffness, it’s multiple changes from soft > stiff > soft?
- Does the extracellular matrix the cell is adhered on affect the force transmission, long-range sensing?
- Are the cells at the leading edge vs. the lagging edge exhibit different phenotypes after apply gradient edge if removed from rest of the population? Are there genetic changes?
- Must think about long-range sensing! Forces from the core (proliferation?), from the environment?
- How can this be translated to 3-D; does the cell acknowledge its own polarity differently in 3D vs. 2D?
- Cool quantitative analysis! Can be used as basis for 3D, though will necessarily need to be pretty different.