Mechanical forces are known to play important roles in many intrinsic and collective cellular processes.  For example, recent studies have highlighted the function of intercellular forces in development, tissue healing and cancer invasion.  However, in contrast to the extensive mechanical studies between cells and extracellular matrices, mechanotransduction between individual cells are still poorly understood, which is mainly due to the lack of tools to measure intercellular forces within a physiological context.  To solve this problem, we have recently developed a series of membrane-anchored DNA hairpin probes to image and quantify tensile forces at cell-cell junctions.  Here, by chemically linking DNA with a cholesterol or phospholipid, DNA probes can self-assemble onto cell membranes after a brief incubation.  Our probe consists of three hybridized DNA strands: a stem-loop DNA hairpin, a ligand-modified strand with dye, and a lipid anchor strand with quencher.  When the tensile force between the ligand and neighboring cell receptor exceeds the threshold force to unfold the DNA hairpin, a drastic increase in the fluorescence intensity is observed due to the separation of the dye-quencher pair.  These DNA-based tools are unique in their compatibility with readily accessible fluorescence microscopes and their ease of preparation and use.  As a result, these DNA probes have started to be popular in mechanobiology.  In this study, I will introduce three types of DNA-based force probes that we have recently developed for (1) visualizing intercellular forces using all commercially available DNA strands, (2) quantifying a large range of tensile forces using ratiometric DNAMeter probes, and (3) multiplexed quantification of several intercellular ligand-receptor pairs based on fluorescence lifetime imaging probes.  Using integrin- and cadherin-based adhesions as the examples, we have shown how mechanical forces will contribute in the process of collective cell migration, wound healing, and epithelial-mesenchymal transition.

Imaging and quantifying intercellular forces with DNA-based fluorescent probes

ACS Spring Meeting 2021

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