# Landscape expansion microscopy reveals interactions between membrane and phase-separated organelles

## TL;DR

A new microscopy technique called land-ExM reveals detailed 3D interactions between cell membranes and phase-separated structures like stress granules.

## Contribution

land-ExM introduces a novel method for high-contrast superresolution imaging of both proteins and lipids in cells.

## Key findings

- land-ExM enables visualization of 3D interactions between membrane-bound organelles and phase-separated condensates.
- The method reveals triple-organellar contact sites involving stress granules, nuclear tunnels, and nucleoli.
- Self-retention trifunctional anchors improve signal-to-noise for accurate ultrastructural imaging.

## Abstract

Zhuang et al. introduce land-ExM, a superresolution approach that simultaneously maps protein and lipid ultrastructure in cells with high contrast. This method visualizes 3D interactions between membrane-bound organelles and phase-separated condensates, uncovering organelle contact sites such as stress granules at nuclear tunnels adjacent to nucleoli.

Landscape expansion microscopy (land-ExM) is a light microscopy technique that visualizes both the lipid and protein ultrastructural context of cells. Achieving this level of detail requires both superresolution and a high signal-to-noise ratio. Although expansion microscopy (ExM) provides superresolution, obtaining high signal-to-noise images of both proteins and lipids remains challenging. land-ExM overcomes this limitation by using self-retention trifunctional anchors to significantly enhance protein and lipid signals in expanded samples. This improvement enables the accurate visualization of diverse membrane organelles and phase separations, as well as the 3D visualization of their contact sites. As a demonstration, we revealed triple-organellar contact sites among the stress granule, the nuclear tunnel, and the nucleolus. Overall, land-ExM offers a high-contrast superresolution platform that advances our understanding of how cells spatially coordinate interactions between membrane organelles and phase separations.