Mathematical modelling of actin polymerization in biological condensates

Fynn Wolf

University of Bergen

"Mathematical modelling of actin polymerization in biological condensates"

Biological condensates are membraneless organelles within the cell or the nucleus which perform an array of different tasks and typically consist of DNA/RNA and protein. Actin is a protein that exists in most eukaryotic cells and transitions between monomeric and filamentous states. In its filamentous state, actin forms networks, which perform vital tasks inside the cell. Recent research has shown interactions between biological condensates and cytoskeletal filaments, such as actin. The focus of these works was on morphological changes of condensates, transportation of condensates along cytoskeletal structures and on bundling of actin filaments inside condensates. While works have shown that condensates facilitate actin polymerization, a theoretical mathematical description of the cooperativity between condensates and actin polymerization is still missing. In this work we use a master equation to capture the polymerization kinetics of actin in a multicompartment system of condensates and dilute phase containing monomeric and filamentous actin. We believe that the model will allow us to make predictions about the number and length of fibers polymerized inside condensates. The findings of this study will hopefully further our understanding of the cooperative behavior between actin and biological condensates and help us understand how biological condensates are involved in the creation and maintenance of the actin networks inside the cell.

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