No abstract

Dissemination of transformed cells is a key process in metastasis. Despite its importance, how transformed cells disseminate from an intact tissue and enter the circulation is poorly understood. Here, we use a fully developed tissue, Drosophila midgut, and describe the morphologically distinct steps and the cellular events occurring over the course of Ras V12transformed cell dissemination. Notably, Ras V12-transformed cells formed the Actin-and Cortactin-rich invasive protrusions that were important for breaching the extracellular matrix (ECM) and visceral muscle. Furthermore, we uncovered the essential roles of the mechanosensory channel Piezo in orchestrating dissemination of Ras V12-transformed cells. Collectively, our study establishes an in vivo model for studying how transformed cells migrate out from a complex tissue and provides unique insights into the roles of Piezo in invasive cell behavior.

Given the role of E-cadherin (E-cad) in holding epithelial cells together, an inverse relationship between E-cad levels and cell invasion during the epithelial-mesenchymal transition (EMT) and cancer metastasis has been well recognized. Here, we report that E-cad is necessary for the invasiveness of RasV12-transformed intestinal epithelial cells in Drosophila. E-cad/β-catenin disassembles at adherens junctions and assembles at invasive protrusions—the actin- and Cortactin-rich invadopodium-like protrusions associated with the breach of the extracellular matrix (ECM)—during dissemination of RasV12-transformed intestinal epithelial cells. Loss of E-cad impairs the elongation of invasive protrusions and attenuates the ability of RasV12-transformed cells to compromise the ECM. Notably, E-cad and Cortactin affect each other's localization to invasive protrusions. Given the essential roles of Cortactin in cell invasion, our observations indicate that E-cad plays a role in the invasiveness of RasV12-transformed intestinal epithelial cells by controlling Cortactin localization to invasive protrusions. Thus, our study demonstrates that E-cad is a component of invasive protrusions and provides molecular insights into the unconventional role of E-cad in cell dissemination in vivo.

Background: The gut visceral musculature plays essential roles in not only moving substances through the lumen but also maintaining the function and physiology of the gut. Although the development of the visceral musculature has been studied in multiple model organisms, how it degenerates is poorly understood.Results: Here, we employ the Drosophila midgut as a model to demonstrate that the visceral musculature is disrupted by intrinsic and extrinsic factors, such as aging, feeding, chemical-induced tissue damage, and oncogenic transformation in the epithelium. Notably, we define four prominent visceral musculature disruption phenotypes, which we refer as "sprout," "discontinuity," "furcation," and "crossover" of the longitudinal muscle. Given that the occurrence of these phenotypes is increased during aging and under various stresses, we propose that these phenotypes can be used as quantitative readouts of deterioration of the visceral musculature. Intriguingly, administration of a tissuedamaging chemical dextran sulfate sodium (DSS) induced similar visceral musculature disruption phenotypes in zebrafish larvae, indicating that ingestion of a tissue-damaging chemical can disrupt the visceral musculature in a vertebrate as well.Conclusions: Our study provides insights into the deterioration of the gut visceral musculature and lays a groundwork for investigating the underlying mechanisms in Drosophila as well as other animals.