Whole-organ single-cell mapping defines growth dynamics and clonal organization in developing and adult zebrafish livers

* WAO-ExM image of a 4× expanded adult liver covered a volume of $9.6 \times 21.2 \times 5.3 \text{ mm}^3$.
* A 10× expanded 7 dpf larval liver had a volume of $0.54 \times 0.54 \times 0.54 \text{ mm}^3$.
* WAO-ExM image of a ventral liver lobe was used to show hepatocyte clones overlaid with DAPI nuclear signals.
* A 4× expanded adult heart showed $\text{Tg}(\text{tcf21}:\text{nuceGFP})$-labeled epicardial cells in a $6.4 \times 6.4 \times 3.0 \text{ mm}^3$ volume.
* WAO-ExM images of an expanded adult pancreas showed $\text{Tg}(\text{ins}:\text{H2A-EGFP})$-labeled beta cells in a $1.7 \times 1.7 \times 0.9 \text{ mm}^3$ volume.
* Imaging of the 7 dpf liver using lightsheet microscopy covered a volume of $2.8 \times 2.8 \times 2.0 \text{ mm}^3$.
* The zebrafish liver showed cell lineage tracing identifying hepatoblast contribution to cell lineages and growth dynamics.

The underlying theme involves utilizing advanced imaging techniques, specifically expansion microscopy (WAO-ExM) and light-sheet microscopy, to achieve nanoscale resolution profiling of complex, large-scale biological structures in developing and adult tissues across zebrafish. This methodology bridges the gap between macroscopic organ development and subcellular molecular architecture, allowing for the visualization of cellular lineage tracking and spatial organization within expanded samples. A key pattern emerges in the application of these methods: using tissue expansion not just for structural reconstruction but as a mechanism to reveal cell-autonomous processes—such as nuclear chromatin architecture or clonal domains—that are otherwise inaccessible at standard resolution. The implications suggest a shift from observing static morphology to mapping dynamic, spatially resolved molecular interactions during organogenesis and regeneration. The reliance on transgenic zebrafish models suggests an effort to leverage these tools for understanding developmental biology and disease states in a living system context.
Which assumptions about the fidelity of expansion microscopy scales are being made when extrapolating subcellular detail across vastly expanded volumes? How does the ability to map cell lineages inform our understanding of the constraints on epigenetic plasticity during organ regeneration, and what are the ethical considerations when applying these high-resolution tools to dynamic developmental processes in model organisms?