Superresolution on the SPOT: Imaging Achieves Optical Sectioning

A technique called SPOT (spectrum and polarization optical tomography) is providing researchers with a “street view” of lipid membranes surrounding cell organelles, thereby allowing insight into lipid dynamics. The work is the result of a collaboration between Peking University and the University of Technology Sydney-Southern University of Science and Technology (UTS-SUStech) Joint Research Centre for Biomedical Materials and Devices.

The lipid membranes surrounding organelles play a vital role in a cell’s dynamics, though their study has proved challenging due to the limitations of superresolution microscopy techniques.

“Their shape, composition, and phase synergistically regulate biophysical membrane properties, membrane protein function, and lipid-protein interactions,” said lead author Karl Zhangao of UTS-SUStech Joint Research Centre. “However, it is challenging to observe such a level of complexity due to their similar chemical composition.”

In using a dye that universally stains lipid membranes, SPOT is able to simultaneously reveal lipid membrane morphology, polarity, and phase from measuring the intensity, spectrum, and polarization, respectively. In tandem with lipophilic probes, the team successfully revealed more than 10 types of organelles simultaneously, enabling them to reveal the lipid dynamics.

With the platform established at SUStech, the researchers observed the multiorganelle interactive activities of cell division, lipid dynamics during plasma membrane separation, tunneling nanotubules formation, and mitochondrial cristae dissociation.

Time-lapse high-dimensional superresolution imaging of the late-stage division of two U2-OS cells. Courtesy of Karl Zhangao et al.

“This is the first time researchers have been able to quantitatively study the lipid heterogeneity inside subcellular organelles,” said senior author Dayong Jin, director of the UTS-SUStech Joint Research Centre and director of the UTS Institute for Biomedical Materials and Devices. The method, he said, will advance the knowledge of how cells function — for example, diagnosing when a transportation doesn’t work properly within a cell and monitoring the progression of disease.

“With such information it isn’t too big a leap to identify pathways for potential drug treatments, as well as examine their efficacy right on the SPOT,” he said.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-020-19747-0).