Introducing the nucleus into the Cellular Potts Model: a multiscale approach for cell migration studies

Cell migration is fundamental in multicellular organisms. It is involved, e.g., in early development, in maintenance of tissue homeostasis, in the functioning in the immune system. Importantly, besides cytoplasmic deformability, the nucleus stiffness can limit cellular migration through channels in dense environments. In order to adequately model this process, recent work has proposed compartmental Cellular Potts Models, in which one CPM compartment represents the cytoplasm, and a second, stiffer compartment is embedded within the cytoplasmic compartment to model the nucleus. Here we show that the increased stiffness of the nucleus introduces an artificial friction with the lattice. We provide quantitative data showing that the increased nuclear stiffness can visibly slow down the cytoplasmic movement, thus producing an artifact in speed quantification. We present an alternative approach to model the nucleus that addresses this issue: a node-based CPM-independent layer, which maintains the deformability characteristics, but does not directly influence the cytoplasmic movement.