Supervisor: Francesca Serra
Many types of living cells are spontaneously elongated and align with their neighbors. In this, their behavior is similar to that of liquid crystals, complex fluids commonly found in displays. In cells this affects the patterns of cell migration and the cell-cell communication. In well-aligned cell layers (or in liquid crystals) one can define an average direction, described as a vector called the nematic director. However, there can be many situations where a uniform alignment of cells everywhere is impossible. In these scenarios the cells form “topological defects”, small regions where the order is disrupted and the cells’ orientation is not uniform. There is increasing evidence that these defects play a key role in the organization of cell layers and of tissues. In my lab, we control and impose topological defects by growing cells on patterned substrates and we analyze their behavior near and far from the defects.
In this project, we will study defects with high “topological charge”, or high distortion of the monolayers. These are rarely seen in cell monolayers but they are seen more frequently in vivo. We can however impose these unusual defects by patterning small ridges on the substrates, which help guide the cells. We will grow two different cell types on patterned substrates, quantify their alignment far from the center of the defects and observe the cells’ shape and behavior near the defects.
A closely related question is: how well can various cell type adapt to strong distortions? How do cells behave near corners and sharp edges? We know from liquid crystal physics that topological defects often form near sharp edges, so we would like to explore the cell orientation and defect formation near sharp edges and corners.
The project(s) will involve fabricating the patterned substrates starting from a template (PDMS soft lithography), growing cells on them, observing them with optical microscopy and fluorescence microscopy and analyzing the data with available programs in ImageJ and Matlab.