Tamori, Y. | bioRxiv Science

bioRxiv2022

Attachment/detachment of cortical myosin regulates cell junction exchange during cell rearrangement

Epithelial cells remodel cell adhesion and change their neighbors to shape a tissue. This cell rearrangement proceeds in three steps: the shrinkage of a junction, exchange of junctions, and elongation of the newly generated junction. Herein, by combining live imaging and physical modeling, we showed that the formation of myosin-II (myo-II) cables around the cell vertices underlies the exchange of junctions. The local and transient detachment of myo-II from the cell cortex is coupled with the junction shrinkage and elongation via an interplay between the LIM domain-containing protein Jub and the tricellular junction protein M6. Furthermore, we developed a mechanical model based on the wetting theory and clarified the way by which the physical properties of myo-II cables are integrated with the junction geometry to induce the transition between the attached and detached states and support the unidirectionality of cell rearrangement. Collectively, the present study elucidates the orchestration of geometry, mechanics and signaling for exchanging junctions.

cell biology↗

bioRxiv2021

Tumor-Cell Invasion Initiates at Invasion Hotspots, an Epithelial Tissue-Intrinsic Microenvironment

Malignant cancers emerge in epithelial tissues through a progressive process in which a single transformed mutant cell becomes tumorigenic and invasive. Although numerous genes involved in the malignant transformation of cancer cells have been described, how tumor cells launch an invasion into the basal side of epithelial tissues remains elusive. Here, using a Drosophila wing imaginal disc epithelia, we show that genetically mosaic clones of cells mutant for a neoplastic-tumor-suppressor gene (nTSG) in combination with the oncogenic Ras (RasV12) expression initiate invasion into the basal side of the epithelial layer at specific spots in the epithelial tissue. In this "invasion hotspot", the oncogenic double-mutant cells activate c-Jun N-terminal kinase (JNK) signaling, which causes basal extrusion of the double-mutant cells and destruction of basement membrane through upregulation of a matrix metalloprotease, MMP1. Conversely, in other regions of the epithelial tissue, the double-mutant cells do not strongly activate JNK, deviate from the apical side of the epithelial layer, and show benign tumor growth in the lumen. These data indicate that the onset of tumor-cell invasion is highly dependent on the tissue-intrinsic local microenvironment. Given the conservation of genetic signaling pathways involved in this process, initiation of tumor-cell invasion from invasion hotspots in Drosophila wing imaginal epithelia could help us to understand the developmental mechanisms of invasive cancers.

cancer biology↗