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Published April 8, 2014 | Supplemental Material + Published
Journal Article Open

Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability


Hybridization chain reaction (HCR) provides multiplexed, isothermal, enzyme-free, molecular signal amplification in diverse settings. Within intact vertebrate embryos, where signal-to-background is at a premium, HCR in situ amplification enables simultaneous mapping of multiple target mRNAs, addressing a longstanding challenge in the biological sciences. With this approach, RNA probes complementary to mRNA targets trigger chain reactions in which metastable fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. The properties of HCR lead to straightforward multiplexing, deep sample penetration, high signal-to-background, and sharp subcellular signal localization within fixed whole-mount zebrafish embryos, a standard model system for the study of vertebrate development. However, RNA reagents are expensive and vulnerable to enzymatic degradation. Moreover, the stringent hybridization conditions used to destabilize nonspecific hairpin binding also reduce the energetic driving force for HCR polymerization, creating a trade-off between minimization of background and maximization of signal. Here, we eliminate this trade-off by demonstrating that low background levels can be achieved using permissive in situ amplification conditions (0% formamide, room temperature) and engineer next-generation DNA HCR amplifiers that maximize the free energy benefit per polymerization step while preserving the kinetic trapping property that underlies conditional polymerization, dramatically increasing signal gain, reducing reagent cost, and improving reagent durability.

Additional Information

© 2014 American Chemical Society. ACS AuthorChoice. Received for review November 4, 2013 and accepted March 31, 2014; published online April 8, 2014. Publication Date (Web): April 8, 2014. We thank B. R. Wolfe, J. N. Zadeh, and R. M. Dirks for the use of unpublished multistate sequence design software. We thank L. M. Hochrein, V. Trivedi, J. R. Vieregg, B. R. Wolfe, and S. E. Fraser for helpful discussions and M. Kirk for assistance with bibliography preparation. This work draws on molecular architectures and sequence design algorithms developed within the NSF Molecular Programming Project (NSF-CCF-0832824 and NSF-CCF-1317694) and was funded by the NIH (5R01EB006192), the Gordon and Betty Moore Foundation (GBMF2809), and the Beckman Institute at Caltech (Programmable Molecular Technology Center).

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Published - nn405717p.pdf

Supplemental Material - nn405717p_si_001.pdf

Supplemental Material - nn405717p_si_002.avi


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