In most tissues, cells are tightly adhered to given positions. The haematopoietic and immune systems constitute exceptions to this rule with the capacity to travel and access sites of inflammation or injury in the body. In many pathological conditions, such as metastasis, other cells can acquire the ability to penetrate tissues. Invasion requires alterations in the biology of the invading cell as well as in the integrity of the penetrated barrier. To study the phenomenon of tissue invasion, the EU-funded BB: DICJI (Breaking barriers: Investigating the junctional and mechanobiological changes underlying the ability of Drosophila immune cells to invade an epithelium) project studied Drosophila haemocytes as they move through an epithelial barrier during embryonic development. The goal of the project was to identify the morphological and biophysical changes in the epithelia during this immune cell transmigration. Previous work had shown that these haemocytes require the small GTPase RhoL to alter cadherin expression during invasion. Researchers used immunofluorescence and live imaging to detect changes in the cadherin junctions and the actin network. Adherens junctions are cell to cell connections that keep epithelial cells together and help to withstand mechanical forces. BB: DICJI results indicated that haemocyte migration during Drosophila development causes changes in the cadherin localisation in the neighbouring cells, at least in part through apoptosis. Invasion was also associated with alterations in junctional tension. Collectively, the findings of the study pave the way towards the elucidation of the complex process of cell migration through tissues. The molecular determinants of the process could serve as targets for halting cancer metastasis.
Cell migration, development, cancer, Drosophila, haemocyte, cadherin, adherens junctions