Physics Colloquium - Design Principles of Size-Control in Cellular Structures

How it’s made: Design principles of size-control in cellular structures

Dr. Lishibanya Mohapatra
Lecturer, Post-doctoral Associate
Brandeis University

Abstract:
Cells contain a number of micron-scale structures, whose physiological functions are related to their size. Examples include cytoskeletal elements like mitotic spindle, cilia, and actin cables. Each of these structures is characterized by a narrow size distribution and is composed of molecular building blocks such as tubulin dimers and actin monomers that diffuse in the cytoplasm. A key question is how the sizes of these structures are maintained amid constant turnover of their molecular components. The “limiting-pool” mechanism, which hypothesizes that the size of a structure grows until the pool of available building blocks is depleted, has been extensively studied in answering this question. Using theory and experiments on various cell types, I will illustrate the characteristic features of the limiting-pool mechanism and highlight the importance of utilizing additional size-control mechanisms if the cell is to generate multiple structures of well-defined sizes using a common pool of building blocks. Using examples from biology, I will demonstrate how simulations and size distributions can be used to uncover design principles of size-control in cellular structures.

Speaker Bio:
I like to use theory and modeling to study interesting puzzles in the domain of Quantitative Biology. Specifically, my research has focused on finding an answer to the key question: how cells measure and control the size of their organelles? I use tools from statistical mechanics and computational techniques, and observations from recent experiments to model the growth of these structures and also work closely with my experimental collaborators to design experiments to verify the predictions. Examples of organelles that I’ve studied are actin cables in budding yeast cells, flagella in Chlamydomonas and Giardia, and more recently, the nucleoli. Currently, I am the Co-Director of the Quantitative Biology Research Community (QBReC) at Brandeis University. The HHMI-funded program is designed to give undergraduate students an opportunity to experience academic environment by facilitating research opportunities with Brandeis PIs who are working at the interface of the physical and life sciences. Along with working closely with the graduate student/post-doc advisors to develop projects for the undergraduate students in different labs, I also work with students individually on my independent projects, which are largely based on the question of growth and size-control of cellular organelles.