Summary

Tracking-Zellen in GFP-transgenen Zebrafisch Mit dem Photokonvertierbare PSmOrange-System

Published: February 05, 2016
doi:

Summary

We established the photoconvertible PSmOrange system as a powerful, straight-forward and cost inexpensive tool for in vivo cell tracking in GFP transgenic backgrounds. This protocol describes its application in the zebrafish model system.

Abstract

The rapid development of transparent zebrafish embryos (Danio rerio) in combination with fluorescent labelings of cells and tissues allows visualizing developmental processes as they happen in the living animal. Cells of interest can be labeled by using a tissue specific promoter to drive the expression of a fluorescent protein (FP) for the generation of transgenic lines. Using fluorescent photoconvertible proteins for this purpose additionally allows to precisely follow defined structures within the expression domain. Illuminating the protein in the region of interest, changes its emission spectrum and highlights a particular cell or cell cluster leaving other transgenic cells in their original color. A major limitation is the lack of known promoters for a large number of tissues in the zebrafish. Conversely, gene- and enhancer trap screens have generated enormous transgenic resources discretely labeling literally all embryonic structures mostly with GFP or to a lesser extend red or yellow FPs. An approach to follow defined structures in such transgenic backgrounds would be to additionally introduce a ubiquitous photoconvertible protein, which could be converted in the cell(s) of interest. However, the photoconvertible proteins available involve a green and/or less frequently a red emission state1 and can therefore often not be used to track cells in the FP-background of existing transgenic lines. To circumvent this problem, we have established the PSmOrange system for the zebrafish2,3. Simple microinjection of synthetic mRNA encoding a nuclear form of this protein labels all cell nuclei with orange/red fluorescence. Upon targeted photoconversion of the protein, it switches its emission spectrum to far red. The quantum efficiency and stability of the protein makes PSmOrange a superb cell-tracking tool for zebrafish and possibly other teleost species.

Introduction

Exponentially improving imaging techniques allow following developmental processes over time periods of up to about four consecutive days3. In zebrafish and many other animal model systems, specific cells, tissues, axonal or vascular structures are marked by transgenic green or sometimes red or yellow fluorescent proteins to facilitate visualization. However, in most transgenic lines the transgene is not specifically expressed in the cells of interest but also additional structures, which hinders the precise tracking of for instance single cells or groups of cells.

Fluorescent photoconvertible proteins are well suited for cell tracking during embryonic development. The prerequisites for the application of such proteins are a long-lived nature, a well-separated emission range upon conversion and bright fluorescence. Available photoconvertible proteins comprise those that change their emission range upon conversion such as Kaede4, KiGR5, mEos26, PS-CFP2 or Dendra27 and others which are only fluorescent when photoactivated (PAmCherry8, PAGFP9 or PATagRFP10). Their applications to track cells in existing FP-transgenic animals are however limited as they often involve a green fluorescent state or do not fulfill all of the above criteria. Only recently, Subach and colleagues reported the PSmOrange protein, which changes its emission from orange/red to far red upon photoconversion and was successfully applied in cells in culture and cultured cells injected into mice2.

To investigate the protein’s suitability for cell tracking in a living embryo, we generated an expression construct for the microinjection of nuclear-tagged H2B-PSmOrange into zebrafish embryos. We find that the protein fulfills all prerequisites for successful cell tracking in GFP transgenic backgrounds during the first 4 (and possibly more) days of zebrafish embryonic development. During this time, most of the cell migratory events are completed in fish making the PSmOrange system an excellent addition to the zebrafish toolkit.

Protocol

1. H2B-PSmOrange mRNA in vitro-Transkription und mRNA Purification Linearisieren die H2B-PSmOrange enthält pCS2 + Plasmid, das die NotI-Restriktionsenzym unter Verwendung von nach den Anweisungen des Herstellers. Hinweis: Führen Sie die nächsten Schritte mit geeigneten Schutzmaßnahmen wie Handschuhe und Kittel mRNA Verschmutzung und Verschlechterung zu verhindern. Reinige den linearisierten DNA einer PCR Purification Kit oder Phenol-Chloroform-basierte Verfahren nach Herstellerpr…

Representative Results

1 veranschaulicht ein Beispiel des PSmOrange Photosystem. Die Zirbeldrüse Komplex ist eine konservierte Struktur im Wirbeltier dorsalen Zwischenhirn. Wie in vielen anderen Wirbeltieren besteht dieser Komplex der Pinealorgan in der Mitte des Zwischenhirns und den linksseitigen parapineal Zellen. Elegant, aber zeitaufwendig Uncaging Experimente zeigten, dass parapineal Zellen 13 in den vorderen Teil des Pinealorgan stammen. In tg (foxD3: GFP); tg (FLH: GFP) tra…

Discussion

Transgene Embryonen fluoreszierenden Reporter trägt grundlegend zu verstehen, die embryonale Entwicklung geholfen. Es besteht jedoch immer noch die wesentliche Notwendigkeit für Promotoren die spezifische Visualisierung von besonderen Strukturen zu erleichtern. In ihrer Abwesenheit, verlassen sich die Forscher auf Techniken wie die Photokonversion von fluoreszierenden Proteinen über den Ursprung und die Entwicklung ihrer Struktur von Interesse zu erfahren. Dies wiederum ist eine wesentliche Voraussetzung, die molekul…

Divulgazioni

The authors have nothing to disclose.

Acknowledgements

We thank O. Subach for providing the original H2B-PSmOrange plasmid and our fish facility team for fish care. We are grateful to the Nikon Imaging Center at the University of Heidelberg for access to microscopy equipment and analysis software. We acknowledge the support of the Core Facility Live Cell Imaging Mannheim at the CBTM (DFG INST 91027/10-1 FUGG). This work was supported by the Excellenzcluster CellNetworks, EcTop Spatio-temporal coordination of signaling processes (EcTop 2), University of Heidelberg to C.A.B. and the Medical Faculty Mannheim of the University Heidelberg and the DFG (FOR 1036/2, 298/3-1 and 298/6-1) to M.C.

Materials

PCR Purification Kit Qiagen 28104
mMESSAGE mMACHINE SP6 Transcription kit Ambion AM1340
RNeasy MiniElute Cleanup kit Qiagen 74204
Plastic Pasteur alpha laboratories LW4000
Original H2B-PSmOrange Plasmid Addgene 31920 The plasmid described in the paper is available in the Carl lab
FemtoJet Microinjector Eppendorf 5247 000.013
Forceps (5 Inox) NeoLab 2-1633
Lab-Tek II Chambered #1.5 German Coverglass System  Nunc 155382
Nikon A1R+ Nikon GmbH Germany No Number
Nikon PLAN Apo λ 20x air objective  Nikon GmbH Germany No Number
NIS Elements AR Software (v. 4.30.02) Nikon GmbH Germany/Laboratory Imaging No Number

Riferimenti

  1. Lombardo, V. A., Sporbert, A., Abdelilah-Seyfried, S. Cell Tracking Using Photoconvertible Proteins During Zebrafish Development. J. Vis. Exp. (4350), (2012).
  2. Subach, O. M., et al. A photoswitchable orange-to-far-red fluorescent protein, PSmOrange. Nature Methods. 8, 771-777 (2011).
  3. Beretta, C. A., Dross, N., Bankhead, P., Carl, M. The ventral habenulae of zebrafish develop in prosomere 2 dependent on Tcf7l2 function. Neural Development. 8, 19 (2013).
  4. Ando, R., Hama, H., Yamamoto-Hino, M., Mizuno, H., Miyawaki, A. An optical marker based on the UV-induced green-to-red photoconversion of a fluorescent protein. Proc. Natl. Acad. Sci. U.S.A. 99, 12651-12656 (2002).
  5. Habuchi, S., Tsutsui, H., Kochaniak, A. B., Miyawaki, A., van Oijen, A. M. mKikGR, a monomeric photoswitchable fluorescent protein. PLoS One. 3, e3944 (2008).
  6. McKinney, S. A., Murphy, C. S., Hazelwood, K. L., Davidson, M. W., Looger, L. L. A bright and photostable photoconvertible fluorescent protein. Nature Methods. 6, 131-133 (2009).
  7. Chudakov, D. M., Lukyanov, S., Lukyanov, K. A. Tracking intracellular protein movements using photoswitchable fluorescent proteins PS-CFP2 and Dendra2. Nature Protocols. 2, 2024-2032 (2007).
  8. Subach, F. V., et al. Photoactivatable mCherry for high-resolution two-color fluorescence microscopy. Nature Methods. 6, 153-159 (2009).
  9. Patterson, G. H., Lippincott-Schwartz, J. A photoactivatable GFP for selective photolabeling of proteins and cells. Science. 297, 1873-1877 (2002).
  10. Subach, F. V., Patterson, G. H., Renz, M., Lippincott-Schwartz, J., Verkhusha, V. V. Bright monomeric photoactivatable red fluorescent protein for two-color super-resolution sptPALM of live cells. J Am Chem Soc. 132, 6481-6491 (2010).
  11. Rosen, J. N., Sweeney, M. F., Mably, J. D. Microinjection of zebrafish embryos to analyze gene function. J Vis Exp. (25), e1115 (2009).
  12. Concha, M. L., et al. Local tissue interactions across the dorsal midline of the forebrain establish CNS laterality. Neuron. 39, 423-438 (2003).
  13. Auer, T. O., Duroure, K., Concordet, J. P., Del Bene, F. CRISPR/Cas9-mediated conversion of eGFP- into Gal4-transgenic lines in zebrafish. Nature Protocols. 9, 2823-2840 (2014).
  14. Auer, T. O., Duroure, K., De Cian, A., Concordet, J. P., Del Bene, F. Highly efficient CRISPR/Cas9-mediated knock-in in zebrafish by homology-independent DNA repair. Genome Research. 24, 142-153 (2014).
  15. Keller, P. J., Schmidt, A. D., Wittbrodt, J., Stelzer, E. H. Reconstruction of zebrafish early embryonic development by scanned light sheet microscopy. Science. 322, 1065-1069 (2008).

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Citazione di questo articolo
Beretta, C. A., Dross, N., Engel, U., Carl, M. Tracking Cells in GFP-transgenic Zebrafish Using the Photoconvertible PSmOrange System. J. Vis. Exp. (108), e53604, doi:10.3791/53604 (2016).

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