The LS2 initiative: an open-source light-sheet microscope for imaging across scales - PROJECT ABSTRACT Biological tissue is organized over scales of nanometers to centimeters. Understanding individual cells and multi- cellular organization requires simultaneously probing the architecture of tissue across these spatial scales. Recent advances in tissue clearing, expansion, and fluorescence labeling are providing unprecedented access to structural and molecular information from intact tissues. These methods have the potential to accelerate new discoveries across diverse fields of research. Within neuroscience, these techniques offer new possibilities to map neural circuits from synapses to the whole mouse, primate, and human brain. However, fully harnessing molecular imaging across three-dimensional samples at scale requires new advances in microscopy. Standard microscope objectives have limited working distances (< 1 mm) and fields of view (< 1 mm). Therefore, imaging large tissue volumes at high resolution typically requires physical sectioning and extensive image tiling, both of which severely complicate large-scale volumetric imaging. These technical constraints often limit current imaging technologies to imaging small (mm3) volumes at high resolution (<1 µm) or large (cm3) volumes at lower resolution (>1 µm). To address this need, we have developed a new large-scale light-sheet (LS2) microscope. Our LS2 system enables diffraction-limited and aberration-free imaging of centimeter-scale tissues with high contrast, resolution, speed, and ease-of-use (i.e., no tissue sectioning and minimal image tiling) - attributes that are currently unattainable with existing imaging technologies. By leveraging highly engineered lenses and camera sensors from the electronics metrology industry, the LS2 system achieves a field of view of 10.6 x 8.0 mm (30x larger than previous systems) and 35 mm working distance (10x larger) with a near-isotropic resolution of 1.0 x 1.0 x 2.5 µm. Including stage movement, the system can access a 200 x 52 x 35 mm3 volume without sectioning, at up to 1 gigavoxel/sec. While the LS2 system was designed at the Allen Institute for Neural Dynamics for brain-wide imaging and reconstruction of neural circuits in the mouse brain, it will also be transformative for an array of scientific questions being pursued by many other investigators and institutions. However, for the LS2 system to drive scientific discovery, it is imperative to offer well-documented, supported hardware and software designs, alongside educational resources—elements crucial to lowering the adoption barrier. The work proposed here will support these efforts, thereby allowing us to maximize the scientific impact of a recently optimized and re-engineered and optimized LS2 system.
