Each cell in a multi-cellular organism contains the same genome, yet the regulatory circuits encoded within this genome implement a developmental program yielding significant spatial heterogeneity and complexity. In situ hybridization methods are an essential tool for elucidating developmental and pathological processes, enabling imaging of mRNA expression in a morphological context from sub-cellular to organismal length scales. Due to variability between specimens, accurate mapping of spatial relationships between the regulatory loci of different genes requires multiplexed experiments in which multiple mRNAs are imaged in a single biological sample. With current in situ hybridization approaches, it is challenging to simultaneously detect the expression of multiple target mRNAs within intact vertebrate embryos. This shortcoming is a significant impediment to the study of interacting regulatory elements in systems most relevant to human development and disease. Here, we draw on concepts from the field of nucleic acid nanotechnology to design and validate in situ amplifiers based on the mechanism of hybridization chain reaction (HCR). Using this approach, RNA probes complementary to mRNA targets trigger chain reactions in which fluorophore-labeled RNA hairpins self-assemble into tethered fluorescent amplification polymers. During the first funding period, we engineered orthogonal HCR amplifiers that operate independently in the same sample at the same time. Robust performance was achieved when imaging five target mRNAs simultaneously in fixed whole-mount and cross-sectioned zebrafish embryos. Moreover, HCR amplifiers exhibited excellent sample penetration, high signal-to-background, and sharp signal localization. During the second funding period, we will extend the core HCR in situ amplification technology to pursue unprecedented quantitative imaging goals in vertebrate embryos, to diversify the classes of targets and organisms for which the technology is validated and optimized, and to engineer next-generation HCR in situ amplifiers with improved properties. Our major goals are: Accurate and precise relative quantitation of mRNA abundance across whole-embryo images. Sub-cellular imaging of single mRNA transcripts with quantitative yield in whole-mount zebrafish embryos. Multiplexed mapping of miRNAs and alternatively spliced mRNAs with high signal-to-background in whole- mount zebrafish embryos. Generalizing HCR in situ amplification for use in diverse organisms. Engineering next-generation HCR in situ amplifiers with dramatically improved gain, uniformity, speed, and cost. Realization of these goals would have a broad impact on research in the biological sciences, providing an unprecedented combination of multiplexing, quantitation, sensitivity, and resolution for the study of interacting RNA regulatory elements within intact vertebrate embryos and other diverse biological samples.

Public Health Relevance

We propose to engineer molecular instruments for quantitatively mapping the expression patterns of multiple genetic regulatory elements at the same time within a single intact vertebrate embryo. This technology will provide biologists with crucial tools for elucidating the roles that biological circuits play in human development and disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Type
Research Project (R01)
Project #
2R01EB006192-05A1
Application #
8239446
Study Section
Special Emphasis Panel (ZRG1-IMST-L (90))
Program Officer
Korte, Brenda
Project Start
2005-09-22
Project End
2015-08-31
Budget Start
2011-09-15
Budget End
2012-08-31
Support Year
5
Fiscal Year
2011
Total Cost
$424,858
Indirect Cost
Name
California Institute of Technology
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
009584210
City
Pasadena
State
CA
Country
United States
Zip Code
91125
Choi, Harry M T; Schwarzkopf, Maayan; Fornace, Mark E et al. (2018) Third-generation in situ hybridization chain reaction: multiplexed, quantitative, sensitive, versatile, robust. Development 145:
Trivedi, Vikas; Choi, Harry M T; Fraser, Scott E et al. (2018) Multidimensional quantitative analysis of mRNA expression within intact vertebrate embryos. Development 145:
Choi, Harry M T; Calvert, Colby R; Husain, Naeem et al. (2016) Mapping a multiplexed zoo of mRNA expression. Development 143:3632-3637
Schwarzkopf, Maayan; Pierce, Niles A (2016) Multiplexed miRNA northern blots via hybridization chain reaction. Nucleic Acids Res 44:e129
Shah, Sheel; Lubeck, Eric; Schwarzkopf, Maayan et al. (2016) Single-molecule RNA detection at depth by hybridization chain reaction and tissue hydrogel embedding and clearing. Development 143:2862-7
Huss, David; Choi, Harry M T; Readhead, Carol et al. (2015) Combinatorial analysis of mRNA expression patterns in mouse embryos using hybridization chain reaction. Cold Spring Harb Protoc 2015:259-68
Choi, Harry M T; Beck, Victor A; Pierce, Niles A (2014) Next-generation in situ hybridization chain reaction: higher gain, lower cost, greater durability. ACS Nano 8:4284-94
Rosenthal, Adam Z; Zhang, Xinning; Lucey, Kaitlyn S et al. (2013) Localizing transcripts to single cells suggests an important role of uncultured deltaproteobacteria in the termite gut hydrogen economy. Proc Natl Acad Sci U S A 110:16163-8
Tu, Chuqiao; Osborne, Elizabeth A; Louie, Angelique Y (2011) Activatable T? and T? magnetic resonance imaging contrast agents. Ann Biomed Eng 39:1335-48
Tu, Chuqiao; Ma, Xuchu; Pantazis, Periklis et al. (2010) Paramagnetic, silicon quantum dots for magnetic resonance and two-photon imaging of macrophages. J Am Chem Soc 132:2016-23

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