A quantitative analysis of forces and mechanics during interkinetic nuclear migration in the developing zebrafish embryo.

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Interkinetic Nuclear Migration (IKNM) describes cell cycle phase dependent nuclear movements in pseudostratified epithelia in a broad range of developing organisms from the anemone nematostella to the mammalian neocortex. Despite the fact that nuclear movements during IKNM are thought to be intimately tied to successful proliferation and subsequent differentiation, not much is known about the relationship between IKNM and developmental programs. Recently some progress has been made in understanding how distinct proteins, especially cytoskeletal elements and their motors, influence nuclear movement during IKNM on a single cell basis. What is still lacking however is an appreciation of the phenomenon in space and time taking all epithelial nuclei and other subcellular arrangements into consideration. We here aim to elicit nuclear movements beyond the single cell level in zebrafish neuroepithelia in vivo, developing new tracking algorithms that will permit to obtain a holistic picture of all nuclear trajectories. This dataset will help to understand how nuclear movements influence tissue architecture and whether the dynamics of nuclear movement in IKNM are cause or consequence for tight nuclear packing. We will further investigate the links between the tissue scale organization of IKNM and the intracellular forces that lead to it, mainly focusing on the actin and the microtubule cytoskeleton. The outcome of the experimental work will be a prerequisite for a theoretical approach describing IKNM as an emergent property of the tightly packed epithelium, which is the ultimate goal of this proposal.