The cell cortex underlies essential cellular functions, including cell shape changes that facilitate cell division. Comprised of a meshwork of filamentous actin (F-actin) and the plasma membrane, the cortex is remodeled during cytokinesis, physically dividing the cell in two. Recent work has shown that prior to large-scale remodeling, the cortex is also dynamically patterned with coherent subcellular waves of the small GTPase RhoA and F-actin, a phenomenon termed “cortical excitability”. In developing embryos, these waves appear over the entire surface of the cell and then feed into the cytokinetic furrow as cell division progresses and have been proposed to support the rapid and flexible establishment of the division plane. Investigating the mechanisms that support and regulate cortical patterning is currently limited by a lack of technical approaches that can bridge our understanding of biochemical feedback signaling and cortical pattern formation, including the molecular regulation of signaling molecules, membrane dynamics, and cytoskeletal remodeling. A breakthrough in this gap in knowledge has been the development by the applicant of an “artificial cortex”, made from supported lipid bilayers (SLBs) and Xenopus egg extract, which successfully reconstitutes active Rho and F-actin dynamics in a cell-free system. Like in vivo cortical excitability, patterning in the artificial cortex depends on Rho activity and F-actin polymerization. This novel, synthetic approach to investigating cortical patterning is an ideal system for systematically examining the role of individual factors (such as upstream GTPase regulators, membrane composition and fluidity, cell cycle state) in regulating cortical dynamics. Using the artificial cortex as a model for cortical patterning, this proposal for a MOSAIC K99/R00 Award seeks to understand how cortical pattern formation is regulated and how patterning remodels the cell cortex to perform essential functions like cytokinesis. Dr. Landino will investigate the factors that drive cortical wave formation (Aim 1), cytoskeletal remodeling at the cortex (Aim 2), and the role of cortical patterning in supporting successful cell division (Aim 3). The results of this work will expand our knowledge of the molecular regulation of the cortex underlying the emergence of cortical excitability, and the role of dynamic patterning in cell division. Dr. Landino's long-term career goal is to establish an independent research group investigating the mechanisms that regulate cortical patterning and cell division. The proposed training will provide Dr. Landino with additional scientific expertise, including technical training in electron microscopy and preparation of cycling extract, and further establish the artificial cortex as a useful platform for understanding the biochemical and structural regulation of the cell cortex. This award will further Dr. Landino's professional development including formal training in research laboratory management, leading a diverse, equitable, and inclusive workplace, and a tailored plan to support Dr. Landino's application to faculty positions. The exemplary scientific and professional environment at the University of Michigan is ideally suited to support the training outlined in this proposal and ensure Dr. Landino's success in launching an independent research program.

PROJECT NARRATIVE The cell cortex is the outermost layer of the cell, and it is remodeled to support changes in cell shape, including pinching the cell in two during the final stage of cell division; failure to complete this process is correlated with disease states like cancer. Before these shape changes occur, the cortex is dynamically patterned into waves of signaling and structural proteins. The work proposed here will investigate how and why these patterns form and define the role of cortical patterning in supporting successful cell division.