Illuminating Dynamic Processes in the Embryogenesis of Caenorhabditis Elegans with Lighsheet Microscopy

Abstract

Understanding dynamic processes in cells and multicellular systems requires spatiotemporally resolved imaging techniques with low photobleaching and -toxicity. Following this demand, single-plane illumination microscopes (SPIMs) have recently emerged as powerful tools. Using a custom-made SPIM setup that combines rapid widefield detection with optical sectioning and reduced bleaching, we have performed long-term, three-dimensional in-vivo imaging on early embryos of the small nematode Caenorhabditis elegans [1]. Based on our SPIM data, we were able to quantify the movement and arrangment of cells during early embryogenesis. The remarkable similarity of individual cell trajectories across different embryos is well captured by a simple model that mainly considers mechanical interactions of cells [1]. Going beyond mere imaging, we have also implemented a SPIM-based fluorescence correlation spectroscopy (FCS) approach, which allows for quantifying protein diffusion in the early embryo at high spatiotemporal resolution. As a first application, we have determined spatially resolved diffusion maps of the peripheral membrane protein PLC1δ1 in the cytoplasm and on the plasma membrane of worm embryos in the one- and two-cell stage. The obtained results compare favorably to previous reports on the same protein construct. We also have determined time-resolved diffusion maps of the protein PIE-1 which highlight a significantly varying mobility of the protein along the anterior-posterior axis of the embryo before the first, asymmetric cell division. Hence, SPIM-FCS is a well-suited tool for assessing diffusional transport in developmental model organisms. [1] Fickentscher, Struntz & Weiss, Biophys. J. 105, 1805 (2013).