Engineering photostable fluorescent proteins and biosensors using transcriptomic mining and massive-throughput single-cell screening

Active Project Grant Awarded Last action

Award ID
R01EB032854
Recipient
Awarding agency
Obligated
$7,734,170

Award facts

Completion date 94% complete
Originally
Place of performance
Texas, USA

Award details come from USAspending.gov.

Description

Abstract
Fluorescent proteins are ubiquitous reagents in the biomedical sciences for reporting gene expression, protein and nucleic acid localization, cell shape, and cellular activity. However, fluorescent proteins (FPS) become progressively dimmer - they photobleach - with repeated or prolonged illumination. Photobleaching limits multiple types of biological experiments where photostability is essential, such as single-molecule biophysics and timelapse imaging of cellular activity during development, learning, and aging. Photobleaching often cannot simply be addressed by increasing the excitation light, as high illumination power can induce membrane blebbing, nuclear fragmentation, alterations in the cell cycle, changes to the concentration of intracellular calcium, and, ultimately, cell death. While over two decades of FP engineering has led to a toolbox of bright FPS, less attention has been devoted to improving photostability because of the greater difficulty and lower throughput endured when screening for photostable FPS. Moreover, few studies have attempted to improve photophysical properties under two-photon illumination - a method of choice for deep-tissue imaging - because of technical challenges associated with screening under this imaging modality. The overall objective of this research proposal is, therefore, to develop and apply a color palette of bright and photostable FPS for one- and two-photon imaging in mammalian cells. Our proposal leverages two specialized and synergistic approaches to FP discovery and engineering: (1) spotlight, a new all- optical screening approach developed in DR. ST-pierre's lab that circumvents technical hurdles and enables rapid screening of both brightness and photostability at the single-cell level under one- and two-photon illumination; and (2) transcriptomic and metagenomic mining for novel FPS from marine invertebrates, a technique pioneered by DR. Shaner's lab. Spotlight relies on light patterning technology to selectively illuminate individual cells labeled with fluorophores that can be photoactivated from a DIM to a bright state. The cells are therefore tagged with a unique fluorescence signature that can then be distinguished and retrieved using fluorescence activated cell sorting (facs). Spotlight thus enables screening in dense mixed cultures with single-cell resolution, thereby eclipsing the throughput of traditional well-based approaches. Mining for novel FPS in marine invertebrate transcriptomes and metagenomes will allow US to rapidly identify and characterize hundreds of novel FPS. From this pool of new FPS, we will select the most photostable for engineering with the spotlight pipeline. We will also model their structures to guide site-directed mutagenesis. We propose to leverage these new technologies and assays to develop FPS of different colors that are bright, monomeric, and sufficiently photostable for long-term imaging experiments. We also propose to apply these new FPS to increase the photostability of genetically encoded voltage indicators (gevis), which are fluorescent biosensors whose brightness reports changes in voltage. While gevis are proposing tools for imaging neural electrical activity with exquisite temporal resolution, they require high illumination power for detection and typically bleach in seconds or minutes. Overall, we anticipate that this project will produce bright and photostable fluorophores and biosensors of broad utility for illuminating cellular dynamics and that our procedures will inspire further multi-parameter engineering of imaging probes for long-term imaging.

Transactions

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Subawards

Subrecipient Amount Awarded
University Of California, San Diego Agreement: $203,183 Amd 1: $243,397 Amd 2: $219,057 Amd 3: $19,472 Amd 4: $243,397 Dr. Shaner’s work on this project will focus on identifying novel… $928,506

Quick answers

Who received award R01EB032854?

R01EB032854 was awarded to Baylor College Of Medicine by National Institute of Biomedical Imaging and Bioenginering (National Institutes of Health) on May 1, 2022.

How much is award R01EB032854 worth?

$7,734,170 has been obligated on R01EB032854.

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