Two-Photon-Based Photoactivation in Live Zebrafish Embryos
Summary
Multiphoton microscopy allows control of low energy photons with deep optical penetration and reduced phototoxicity. We describe the use of this technology for live cell labeling in zebrafish embryos. This protocol can be readily adapted for photo-induction of various light-responsive molecules.
Abstract
Photoactivation of target compounds in a living organism has proven a valuable approach to investigate various biological processes such as embryonic development, cellular signaling and adult physiology. In this respect, the use of multi-photon microscopy enables quantitative photoactivation of a given light responsive agent in deep tissues at a single cell resolution. As zebrafish embryos are optically transparent, their development can be monitored in vivo. These traits make the zebrafish a perfect model organism for controlling the activity of a variety of chemical agents and proteins by focused light. Here we describe the use of two-photon microscopy to induce the activation of chemically caged fluorescein, which in turn allows us to follow cell’s destiny in live zebrafish embryos. We use embryos expressing a live genetic landmark (GFP) to locate and precisely target any cells of interest. This procedure can be similarly used for precise light induced activation of proteins, hormones, small molecules and other caged compounds.
Protocol
Discussion
Photo-activatable compounds are molecules whose function is masked until they are illuminated with a specific wavelength (usually UV), inducing a photochemical reaction that converts the molecules into a biologically or chemically active state. These probes provide very powerful tools in cell biology research, since the activation can be precisely controlled temporally and spatially by limiting their exposure to light.
The significant advantage of multi-photon microscopy is its relatively d…
Acknowledgements
Thanks are due to Genia Brodsky for figure graphics; Vyacheslav Kalchenko, Douglas Lutz, and Leonid Roitman for technical advice and assistance with the two-photon uncaging; Maayan Tahor and Suliman Elsadin for technical assistance; Uwe Strahle for kindly providing the neurogenin1 reporter line and Amos Gutnick for comments on this manuscript. The research in the Levkowitz lab is supported by the German-Israeli Foundation (grant number 183/2007); Israel Science Foundation (grant number 928/08) and the Harriet&Marcel Dekker Foundation. G.L. is an incumbent of the Tauro Career Development Chair in Biomedical Research.
Materials
| Material Name | Typ | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Dextran-conjugated 4,5-dimethoxy-2-nitrobenzyl (DMNB) caged fluorescein (10,000 MW dextran, anionic) | Invitrogen | D-3310 | molecular probes | |
| Agarose for injection trough and coated plates | Sigma | A9539 | ||
| Thin Wall Glass Capillaries with filament | World Precision Instruments | TW100F-6 | ||
| Micropipette puller | Sutter Instrument | P-97 | ||
| Microloader tip | Eppendorf | 5242 956.003 | ||
| Pneumatic picopump | World Precision Instruments | PV820 | ||
| Phenylthiourea (PTU) | Sigma | 22290-9 | ||
| Low melting point agarose for embryo mounting | Ultra Pure LMP agarose | 16520100 | ||
| Anti-Fluorescein- alkaline phosphatase (AP) Fab fragments | Roche | 11426338910 | ||
| Fast Red | Roche | 11496549001 |
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