Molecular and mechanical mechanisms coordinating cell rearrangements in 3D during epithelial morphogenesis

/Abstract Cell rearrangements are essential for epithelial tissue remodeling during processes such as development, wound healing, and cancer migration. While prior studies have explored the molecular mechanisms driving these rearrangements, they have largely focused on the apical and basal surfaces due to the accessibility of these regions and the relative ease of 2D image analysis. However, the role of the lateral domain—which spans between the apical and basal surfaces—remains poorly understood. Moreover, how these cellular domains coordinate to drive rearrangements throughout the full tissue depth is still unclear. Recent studies of 3D cell geometries during rearrangements in the Drosophila germband epithelium have revealed that cell rearrangements can initiate at any location along the apical-basal axis and that the associated cell-cell contact remodeling propagates apically and/or basally to complete the process. These findings highlight the crucial role of sub-apical dynamics in driving cell rearrangement and tissue flow. This proposal leverages genetics, live imaging, and physical modeling approaches to uncover how molecular and mechanical cues coordinate across the apical-basal axis to drive cell rearrangement and tissue flow in the germband. In Aim 1, I will investigate the spatial and temporal dynamics of cytoskeletal and adhesion proteins along the apical-basal axis using live and fixed imaging, and correlate their localization patterns with rearrangement initiation location and propagation direction. I hypothesize that proteins such as actomyosin and its regulators exhibit distinct patterns in the lateral domain that orchestrate full cell rearrangement along the apical-basal axis. By comparing protein localization patterns during cell rearrangement events in wild-type embryos, genetic mutants, and chemically perturbed conditions, I aim to uncover the molecular organization underlying the initiation and propagation of cell rearrangements in 3D. In Aim 2, I will quantify mechanical tension during rearrangements using the variational method of stress inference (VMSI). I propose that actomyosin-generated tension, traditionally associated with the apical domain, also plays an active role in initiating and propagating rearrangement in the sub-apical domain. By mapping tension across the tissue depth and linking it to protein localization and rearrangement behavior, I will dissect the physical forces and molecular mechanisms that drive 3D cell rearrangement. Together, these studies will provide critical insights into how epithelial cells integrate molecular signals and mechanical forces along the apical-basal axis to coordinate efficient cell rearrangement across the tissue depth, offering broader implications for understanding morphogenesis, wound healing, and cancer invasion in three dimensions. Project Number: 1F31HD121390-01 | Fiscal Year: 2026 | NIH Institute/Center: Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) | Principal Investigator: Erika Kusaka | Institution: COLUMBIA UNIV NEW YORK MORNINGSIDE, NEW YORK, NY | Award Amount: $50,114 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F05-D (21)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11318427