In conversation: Michelle Itano on ASCB 2024 and the latest developments in immersion microscopy

In this interview feature, we catch up with our Editor-in-Chief, Michelle Itano (University of North Carolina at Chapel Hill, NC, USA) to discuss her recent experiences at the annual meeting of the American Society for Cell Biology (ASCB; 14–18 December 2024; CA, USA).

Read on for an insight into the key trends at the conference, the developments empowering the investigation of inter-organelle contacts and a handy new tool that could dramatically improve the practicality of immersion microscopy.

Which presentations did you most enjoy at the conference?

That’s hard. The talks on offer were excellent and presented a wide variety of topics, which pushed me to go to lots that were slightly outside my usual area of expertise to broaden my knowledge of the field. One talk that really captured me, and seemingly lots of other people as it was really well attended, was the art and science session, which was followed up with an art and science show into the evening

There were lots of big names in science presentation and art there but there was also a great range to the interpretation of ‘art’. So, we had a presentation from a chemistry professor, who had encouraged her students to present their work in an ‘X Factor’ style competition, which featured lots of genres like rap and artistic expressions beyond drawn art.

Then, she got her students to internalize the rule that ‘if you can’t explain it simply, you don’t understand it well enough’ by getting them to make children’s books about complex scientific topics. It was really cool to see the engagement that was generated from these approaches, especially with a topic like chemistry, which many people struggle to learn and memorize. Then, there was a talk from a professor who makes comics, explaining how drawing comics can help people understand complex issues.

The final keynote by Pietro De Camilli (Yale, CT, USA) explored lysosome maturation. It had a big focus on contacts and how you can capture the critical transient interactions inside a single cell, highlighting the potential disruption presented by the necessary labeling of the components in these interactions. It was fascinating to get into the details with him on the labeling of inner or outer membranes and the markers to look out for when organelles make contact and fuse.

Were there any key themes to the meeting?

A big theme of the meeting, which permeated many of the sessions, was organelle contacts: mitochondria interacting with the ER or plasma membrane or cytoskeleton structures interacting with the nuclear membrane, for example. There were a surprising number of presentations discussing organelle contacts in different contexts, such as in specific cells like neurons; even in the evolutionary biology session there was a fascinating presentation on the interactions between mitochondria and lysosomes.

I think as developments in imaging such as expansion microscopy have improved resolution and become more commonplace, we have been able to see interactions between organelles occurring at specific sites. Evolving techniques like timelapse imaging has enabled us to ask questions about these interactions, for instance whether they induce a deformation of the membrane, stimulate some form of molecule trafficking or trigger different functions. These investigations have also been assisted by turbo ID type and RNA labeling techniques that link to correlative sequencing, all of which received lots of attention at the conference.

Were any of the imaging techniques used to investigate organelle interactions particularly innovative?

Sarah Cohen (University of North Carolina at Chapel Hill) has received a lot of press recently for her work, in which she labels seven organelles all at once, and then does spectral unmixing to track them. I saw a presentation from a student of mine who presented their data as a spatial UMAP, turning imaging data into spatial genetics displays for analysis, which is the first time I’d seen something like that. These interactions are so complex that we haven’t been able to display them in such a visual format of networks and UMAPs before now.

This could prove to be a fantastic approach with which to query complex networks of interactions and identify those that drive functionality. Previously we would have been attempting to do this by eye, which often proves impossible, but the computer can assess 150 connections at once and then tell you those most statistically relevant.

Expansion microscopy and focused ion beam microscopy-secondary ion mass spectrometry (FIB-SIMS) were also discussed in many sessions as tools with which to interrogate these interactions at the molecular and membrane level, revealing whether the organelle membranes are wrapping, breaking or forming a foot at these contact points.

Were there any exciting technological developments on the exhibit floor?

In the microscopy space, almost all of the technological leaders have come out with big updates recently, and there are new companies and collaborations with distributors to make technology more accessible than ever before. One update from Evident Scientific (Tokyo, Japan) that particularly stood out to me was a pad that goes on top of an objective (LUPLAPO25XS) for immersion that won’t dry out. This means that instead of continuing to add the oil, which goes everywhere, you press a pad up against the coverslip and can switch to a dry objective without cleaning or leaving residue. When I saw that I thought to myself, ‘Man, if I could switch from oil to air objectives without cleaning the slide or smearing oil all over it, that would be amazing’.

To explain immersion to anyone currently starting out in microscopy: to improve your resolution, you want to minimize the amount of light you use and the amount of light that is diffracted as it passes through different materials with different refractive indexes. If you don’t use any immersion, after striking the sample, the light must pass back through the glass slide, out into the air and back through the glass of the lens into the microscope. At each of these transitions you will lose light and clarity as it diffracts. By using an immersion that has a very similar refractive index to glass, you make the light travel at the same speed from the lens through to the sample, so less diffraction occurs and you lose less light. This also allows more light to access the sample and reach deeper into it.

However, that immersion is typically a very viscous oil or water – often silicone oil – that can cause smears or lead to the formation of bubbles, or dry out, which then degrades your imaging. For instance, if you find something interesting you may want to switch to a lens with a lower magnification, which may be a dry lens that doesn’t use an immersion, to identify the broader context of the sample you are looking at. During that transition, it is easy to get oil from a high-resolution lens onto the low-magnification one, which means that the lower-resolution lens essentially ceases to work. Oil on the lens causes blurriness and affects the working distance of the lens, and it’s a huge pain. You must clean everything, but again, you still get smears and bubbles. Therefore, the cost of working with that higher resolution can be quite large in actual practice.