

In February, I attended the Biophysical Society Annual Meeting, where the National Lecture was given by Eric Betzig, who won the 2014 Nobel Prize in Chemistry with Stefan Hell and William Moerner for their work in developing superresolution microscopy. His talk (viewable here) was a fascinating and accessible history of the technical advances in this revolutionary technique, punctuated by amazing images with unbelievable detail.

Betzig discussed his non-linear career path, as he has in previous interviews. During a stint of unemployment in 2004, he attended the Biophysics meeting, where he decided he wanted to focus on something with biological relevance. Later that year, he and his friend Herald Hess started building a new microscope that could surpass the Abbe diffraction limit of light microscopes (300 nm). This was the beginnings of his work with superresolution microscopy, an umbrella term for any microscope that can resolve past the Abbe limit.

Despite his many accomplishments, Betzig continues to push the limits of physics so biologists can do better imaging. In fact, a few weeks after he won the Nobel, he published his first paper on lattice light-sheet microscopy in Science (see coverage in the Washington Post).

Betzig says that when cell biologists come to his lab at HHMI's Janelia campus and use the scopes as part of the Visiting Scientists program, they see their samples in a totally new light—literally and figuratively. A recent Science paper from his group's collaboration with Jennifer Lippincott-Schwartz did exactly that for the endoplasmic reticulum (ER). By employing five different types of superresolution microscopy, they were able to visualize the structure and dynamics of the ER at increased speed and resolution. Their images showed that, in contrast to the textbook view of this organelle composed of tubules and flat sheets, the ER is made of tubules with a variety of densities, including a new structure that they call ER matrices. Their data suggest that these matrices are capable of rapid changes in structure, which allows this multifunctional organelle to accommodate the shifting needs of a cell.

Scientists across a range of disciplines are taking advantage of superresolution microscopy to get a new appreciation of the systems they study. Currently, there are many different types of superresolution microscopy, such as STORM, PALM, STED, and SIM. Each technique has its own advantages and drawbacks, as summarized in this SnapShot in Cell. Here, I delve into a few recent publications at Cell Press to show how this technology is changing how biologists are seeing things.

One restriction of existing superresolution microscopes is that only 50–80 nm thickness can be imaged without loss of resolution. A Resource in Cell describes a new microscope and data analysis method to allow 3D imaging in whole cells, achieving 10–-20 nm resolution in cells as thick as 10 microns. To show the usefulness of their scope, the authors image a variety of organelles that have been difficult to image by other microscopy techniques because they span large volumes in the cell. As shown in the Resource's Graphical Abstract (right), they image the cilium, the ER, the mitochondrial network, and the nuclear envelope with increased resolution.

Due to the resolution limits of traditional microscopy, the exact structure of the nuclear lamina, a filamentous network at the inner nuclear membrane that has structural and signaling roles, is unknown. A paper in Current Biology combines a variety of superresolution microscopy techniques with an in vivo protein interaction assay to create a more precise picture of the nuclear lamina. The authors find that A-type and B-type lamins assemble separate but interconnected filament networks. Because each lamin isoform has distinct binding partners, this suggests that the two types of lamin filaments can control the distribution of different proteins in the nuclear periphery.

Superresolution microscopy techniques have also been useful for imaging in dense and fast-moving cellular structures, such as the cells in the nervous system. A recent paper in Cell Reports (in fact, one of the first papers I handled for the journal), uses structured illumination microscopy (SIM) to image the coordinated movements of actin cytoskeletal bundles and vesicles as they emerge from endocytosis in neuronal growth cones. Their experiments showed two endocytic pathways operating in the growth cone: clathrin-dependent endocytosis and a previously unappreciated endophilin-mediated endocytosis. Interestingly, these two pathways show distinct localizations in the cell and appear to be regulated by different mechanisms.

Components of signaling complexes function so closely together that light microscopy cannot resolve the localization and dynamics of individual proteins. A superresolution technique called stochastic optical reconstruction microscopy (STORM) allows single-molecule imaging in vivo. An October 2016 paper in Neuron employs STORM to resolve the spatiotemporal dynamics of individual proteins in ion channel complexes in sensory neurons. Surprisingly, this approach revealed that a protein called AKAP150 acts as a "molecular coupler" that can bring together different complexes of ion channels and signaling proteins in distinct nanodomains in the neuron, suggesting that AKAP150 can precisely modulate the physiological response of the neuron.

These papers are just a sampling of the exciting research being published thanks to advances in microscopy. Superresolution imaging makes it a pretty amazing time to be a biologist; indeed, some scientists are finding renewed enthusiasm for science thanks to the increased resolution.