The role of Mechanics and mechanical feedback in sculpting multicellular systems.

Mahdev Mani (North Western U) 

  Epithelial tissues are experimentally and theoretically tractable living systems in which we can begin     
to explore the mechanisms by which cells change shape, rearrange, and flow, during the course of animal    
development. Manifestly, forces are generated by molecular machines that consume energy, whose             
spatio-temporal pattern of activation is patterned precisely during development. Two questions need to     
be addressed at the biophysical level before we can begin to investigate the role that forces play in      
regulating the biochemistry of cells: 1) statics of tissues, and 2) dynamics of tissues. This talk will    
attempt an answer to both these questions through a combination of theory and analysis of live-imaging     
of early fruit fly development. In particular, it will highlight the presence of extensive                 
degeneracies corresponding to discrete conformal deformations of cells that might play a role in the       
dynamics of cellular shape change, and the role of mechanical-feedback in producing dynamics that are,     
in a precise sense ``orthogonal" to these degeneracies that might play a role in cellular                  
rearrangements.