Meeting Abstract
In the majority of insect lineages, development begins with a series of nuclear divisions and movements within a single shared cytoplasm. First, the nuclei move through the viscous fluid of the cytoplasm, becoming a single layer around the yolk. Then, the nuclei undergo coordinated flows at the periphery of the egg, physically segregating distinct lineages of tissues. Such pre-blastoderm nuclear movements are poorly understood, even in the well-studied Drosophila melanogaster. Moreover, those aspects of post-blastoderm dynamics that have been elucidated in Drosophila are unlikely to be representative of all insects. We are therefore examining these developmental events in an insect that branches basally with respect to the most well-studied model species. We use light sheet microscopy to live-image transgenic embryos of the cricket Gryllus bimaculatus with high temporal resolution. We automatically detect and track nuclei, and then quantitatively characterize early divisions and movements of thousands of nuclei in 3D space for up to 12 hours at a time. This has enabled us to uncover early differentiation of cellular behaviors in the absence of gene expression information. We also describe how the geometric organization of nuclei changes over time, prefiguring the spatial arrangement of newly formed embryonic cells. Lastly, we use injected fluorescent beads to characterize the flow of cytoplasm, and chemical disruptors of the cytoskeleton to probe the mechanistic basis of early nuclear dynamics. Taken together, this work sheds light on how early nuclear movements and fluid mechanics contribute to the formation of the insect embryo.
