Analysis of Microtubule Network Organization and Dynamics in the Yolk Cytoplasm during Zebrafish Epiboly

Morphogenesis describes the coordinated spatial distribution and rearrangement of cells in an organism. To study morphogenesis, I focused on zebrafish epiboly – the coordinated spreading of the blastoderm, which originally sits on top of a large yolk cell, over the yolk surface. Previous work implicated microtubule networks in the yolk cytoplasm (YCL) in this process, but their exact role is unclear. Here I report constant nucleation of new yolk microtubules during epiboly. I found extensive vegetal microtubule growth in the YCL. Furthermore, I demonstrated that the networks can move both animally and vegetally with high variability. In addition, I found evidence to suggest that yolk syncytial nuclei pulling may be facilitated by newly formed microtubules, rather than by existing YCL networks. Together, these results provide insights to the organization and dynamics of the YCL microtubule networks, and in turn their potential function during epiboly.MAS