title: Mesoderm internalisation in Chironomus riparius as an example of ingression creator: Ruhland, Naima Florence Antonie subject: ddc-570 subject: 570 Life sciences subject: ddc-590 subject: 590 Zoological sciences description: Cell movements are an important part of animal multicellularity. They can be found in processes of development and body maintenance, as well in wound healing or cancer formation. A group of cells can either move collectively, showing similar cellular behaviour in all cells, or individually and differ in cellular behaviour. Here, I use the model of early fly gastrulation to investigate how cells differ in their cellular behaviour in the context of single cells movements. Mesoderm internalisation in the insect order of flies (Diptera) shows great differences on a cellular level, while the genetics controlling the process are conserved. This sets the stage to study how single, stochastic cell movement differs from collective cell movement. I focused my work primarily on understanding the cellular behaviour of single cell movement. In the midge Chironomus riparius (C. riparius) mesoderm internalisation has been proposed to be facilitated via single cell ingression. My data, focused on the changes on the apical side of presumptive mesodermal cells, validates again that ingression is a salt and pepper like process. Apical constriction is interrupted by bursts of expansion, that differ in their frequency and length between individual cells. The differences in these bursts cause heterogeneous constriction behaviour between cells. I found strong indications that non-uniform junction mobility is the key component for the stochastic process of apical area reduction. The heterogeneous behaviours of junctions can be found intra- and inter-cellular level, going hand in hand with low cell-cell connectivity, first in the pre-gastrulation stage and then continuously during process of mesoderm internalisation. In addition to apical constriction, neighbour exchange is happening in the mesoderm as well as translocation of cells in response to other gastrulating movements happening simultaneously. It was previously shown that the GPCR signalling ligand Folded gastrulation (Fog), has an effect on the mode of mesoderm internalisation. Going into cellular detail I could show that the major effect of fog over expression on the presumptive mesoderm is not a harmonisation of apical constriction between cells. I have evidence that Fog causes a homogenisation of junction behaviour and induces a stronger cell-cell connectivity. This might enhance stiffening of the tissue, causing the cells to internalise collectively rather than individually. date: 2020 type: Dissertation type: info:eu-repo/semantics/doctoralThesis type: NonPeerReviewed format: application/pdf identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/29206/1/PhD_Thesis_Naima.pdf identifier: DOI:10.11588/heidok.00029206 identifier: urn:nbn:de:bsz:16-heidok-292063 identifier: Ruhland, Naima Florence Antonie (2020) Mesoderm internalisation in Chironomus riparius as an example of ingression. [Dissertation] relation: https://archiv.ub.uni-heidelberg.de/volltextserver/29206/ rights: info:eu-repo/semantics/openAccess rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html language: eng