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Summary: In this protocol, we took a “thermogenetics” approach to detect functional gap junction channels between cells in Drosophila egg chambers. We expressed the thermosensitive cation channel TrpA1-A in the germline using Gal4, and a fluorescent [Ca2+] sensor (GCaMP6), in all follicle cells using the LexA/LexAop system. If gap junctions connect germ cells and follicle cells, we expect a temperature-dependent TRPA1-A-dependent cation influx into the germline from the culture medium to result in a GCaMP signal in follicle cells.For complete details on the use and execution of this protocol, please refer to Miao et al. (2020).

Summary: In collective cell migration, directional protrusions orient cells in response to external cues, which requires coordinated polarity among the migrating cohort. However, the molecular mechanism has not been well defined. Drosophila border cells (BCs) migrate collectively and invade via the confined space between nurse cells, offering an in vivo model to examine how group polarity is organized. Here, we show that the front/back polarity of BCs requires Rap1, hyperactivation of which disrupts cluster polarity and induces misoriented protrusions and loss of asymmetry in the actin network. Conversely, hypoactive Rap1 causes fewer protrusions and cluster spinning during migration. A forward genetic screen revealed that downregulation of the Hippo (Hpo) pathway core components hpo or mats enhances the Rap1V12-induced migration defect and misdirected protrusions. Mechanistically, association of Rap1V12 with the kinase domain of Hpo suppresses its activity, which releases Hpo signaling-mediated suppression of F-actin elongation, promoting cellular protrusions in collective cell migration.

Abstract  Cell motility makes essential contributions to normal embryonic development and homeostasis. It is also thought to contribute in important ways to tumor metastasis. Because of this dual importance, cell migration has been extensively studied. The fruit fly Drosophila melanogaster has served as an important model organism for genetic analysis of many aspects of developmental biology, including cell migration. Here we describe the various types of cell movements that have been studied in detail, which represent models for epithelial-to-mesenchymal transition, transepithelial migration, inflammation, wound healing and invasion. We summarize what has been learned about the molecular control of cell migration from genetic studies in the fly. In addition, we describe recent efforts to model tumor metastasis directly in Drosophila by expressing oncogenes and/or mutating tumor suppressor genes. Together these studies suggest that Drosophila has much to offer as a model for varied aspects of tumor metastasis. [ABSTRACT FROM AUTHOR]