Nuclear deformability facilitates apical nuclear migration in the developing zebrafish retina

Abstract

Nuclear positioning is an important aspect of cell and developmental biology. One example is the apical positioning of nuclei in retinal and other neuroepithelia. Here, apical nuclear migration is crucial for correct tissue formation. Cytoskeletal mechanisms that drive nuclei to the apical side have been explored. Yet, whether also nuclear properties influence apical nuclear migration remained comparatively less understood. Lamin A/C expression levels have been shown to be directly related to nuclear deformability. Further, it was shown that many nuclei in early development, including neuroepithelial nuclei, express only low levels of Lamin A/C. Thus, we asked whether increased expression of Lamin A in the densely packed zebrafish retinal neuroepithelium affects nuclear migration phenomena. We find that overexpressing Lamin A in retinal nuclei of single cells or in the whole tissue increased nuclear stiffness and consequently impaired apical positioning. Interestingly, also nuclei of control cells embedded in a Lamin A overexpressing environment displayed impaired apical nuclear migration. When Lamin A is overexpressed at the tissue level this further leads to a delay in mitotic entry. Thus, nuclear material properties, within cells but also in the surrounding environment, can influence nuclear and cell behavior in densely packed neuroepithelia. Overall, this work quantitatively shows a relevance of low Lamin A/C levels in early neuroepithelial development. These findings are most likely also applicable for other developing tissues which feature nuclear and cell motion through crowded environments.