Tissue shape determines actin-dependent nuclear migration mechanisms in neuroepithelia

Abstract

Correct nuclear position is crucial for cellular function and tissue development.Depending on cell context however, cytoskeletal elements responsible for nuclear positioning vary. While these cytoskeletal mechanisms have been intensely studied in single cells, how nuclear positioning is linked to tissue morphology is less clear.Here, we compare apical nuclear positioning in zebrafish neuroepithelia. We find that kinetics and actin-dependent mechanisms of nuclear positioning vary in tissues of different morphology. In straight neuroepithelia nuclear positioning is controlled by Rho-ROCK-dependent myosin contractility. In contrast, in basally constricted neuroepithelia a novel formin-dependent pushing mechanism is found for which we propose a proof-of-principle force generation theory.Overall, our data suggests that correct nuclear positioning is ensured by the adaptability of the cytoskeleton to cell and tissue shape. This in turn leads to robust epithelial maturation across geometries. The conclusion that different nuclear positioning mechanisms are favoured in tissues of different morphology highlights the importance of developmental context for the execution of intracellular processes.

Synchronisation of apical constriction and cell cycle progression is a conserved behaviour of pseudostratified neuroepithelia informed by their tissue geometry

“…The molecular identities of cells derived from this protocol have been extensively studied (Chambers et al, 2009, Strano et al, 2020, but we propose a minimum molecular markers panel which, to our knowledge, is unique to neuroepithelia. Of particular interest is this protocol's relatively understudied ability to induce loss of the nuclear Lamin A/C, which facilitates IKNM in vivo (Yanakieva et al, 2019b). Several other iPSC differentiation protocols have been described which produce pseudostratified cells in 3D aggregates (Lee et al, 2022, Karzbrun et al, 2021, Veenvliet et al, 2021, but direct imaging of their apical surface would not be feasible in those systems.…”

“…These displacements require nuclear deformation, which is opposed by nuclear envelope proteins such as Lamin A/C (Swift et al, 2013). Embryonic neuroepithelia characteristically lack A-type Lamin expression (Jung et al, 2012, Takamori et al, 2018, Yanakieva et al, 2019a and over-expression of Lamin A diminishes their nuclear motility during IKNM (Yanakieva et al, 2019b).…”

Synchronisation of apical constriction and cell cycle progression is a conserved behaviour of pseudostratified neuroepithelia informed by their tissue geometry

“…The molecular identities of cells derived from this protocol have been extensively studied (Chambers et al, 2009, Strano et al, 2020), but we propose a minimum molecular markers panel which, to our knowledge, is unique to neuroepithelia. Of particular interest is this protocol’s relatively understudied ability to induce loss of the nuclear Lamin A/C, which facilitates IKNM in vivo (Yanakieva et al, 2019b). Of greater consequence than their molecular identity for the studies presented here is the morphological characterisation of these iPSC-derived neuroepithelia.…”

Nuclear deformability facilitates apical nuclear migration in the developing zebrafish retina

“…Example of fluid-like behavior of nuclei upon laser ablation in the tissue (by Iskra Yanakieva 35 ). Nuclei are labelled with H2B-RFP.…”

“…It has been shown that in retinal neuroepithelia apical nuclear movement is driven by formin-dependent actin polymerization where actin filaments are not directly linked to the nuclear envelope 16 . Additionally, it was observed that only low levels of Lamin A/C are expressed in these retinal neuroepithelia 16,35 . We thus asked whether overexpression of Lamin A could influence nuclear deformability and mobility.…”