Multi-scale imaging and analysis identify pan-embryo cell dynamics of germlayer formation in zebrafish

Abstract

The coordination of cell movements across spatio-temporal scales ensures precise positioning of organs during vertebrate gastrulation. Mechanisms governing such morphogenetic movements have been studied only within a local region, a single germlayer or in whole embryos without cell identity. Scale-bridging imaging and automated analysis of cell dynamics are needed for a deeper understanding of tissue formation during gastrulation. Here, we report pan-embryo analyses of formation and dynamics of all three germlayers simultaneously within a developing zebrafish embryo. We show that a distinct distribution of cells in each germlayer is established during early gastrulation via cell movement characteristics that are predominantly determined by their position in the embryo. The differences in initial germlayer distributions are subsequently amplified by a global movement, which organizes the organ precursors along the embryonic body axis, giving rise to the blueprint of organ formation. The tools and data are available as a resource for the community.

Variability of an Early Developmental Cell Population Underlies Stochastic Laterality Defects

“…They are the precursors of the Kupffer’s vesicle (KV) ( Melby et al., 1996 , Oteíza et al., 2008 ), the organ that determines left-right asymmetry in the embryo ( Essner et al., 2005 ) ( Figure 1 B). Since the endoderm is the smallest germ layer during early zebrafish development ( Shah et al., 2019 ), and since relatively large fluctuations of DFC numbers between individual embryos were previously reported ( Oteíza et al., 2008 , Gokey et al., 2015 ), we asked whether naturally occurring embryo-to-embryo variation in cell numbers in wild-type embryos could have any phenotypic consequences.

Figure 1 Cell Number Variability during Early Embryogenesis (A) Maximum projection of confocal images of a Tg[ sox17 :GFP] embryo at 75% epiboly stage showing the endoderm (red), DFCs (green), and nuclei (blue).

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Non-Cell-Autonomous Mechanisms in Radial Projection Neuron Migration in the Developing Cerebral Cortex

“…This would enable a direct assessment of non-cell-autonomous effects exerted by the neighboring cells on an individual cell or vice versa. So far, this method has mostly been used to visualize cell and collective migration behaviors in smaller in vivo systems such as, e.g., Drosophila (Krzic et al, 2012;Tomer et al, 2012), zebrafish (Nogare et al, 2017;Hiscock et al, 2018;Shah et al, 2019) and larger systems such as mouse gastrulation and heart tissue (Megason and Fraser, 2007;Stewart et al, 2009;McDole et al, 2018;Yue et al, 2020). In toto imaging mostly involves labeling of all cell membranes so each cell in the organism/microenvironment can be tracked and segmented (Nogare et al, 2017).…”

High-Resolution, Large Imaging Volume, and Multi-View Single Objective Light-Sheet Microscopy

“…Lightsheet microscopy has been particularly impactful in Developmental Biology allowing the first in-toto volumetric reconstructions of embryonic development of model organisms such as Drosophila, Zebrafish, and Mouse 1,2,15 . The ability to image whole developmental arcs, and to follow hundreds of thousands of cells in space and time has shown the potential of light-sheet microscopy in answering long standing questions 15,16 . However, obstacles remain before light-sheet microscopy can completely fulfil its promises: state-of-the-art light-sheet microscopes are often not available commercially, require advanced skills to build, and force complex sample mounting strategies on users -all of which limit widespread adoption.…”