by Keyword: Photoactivation

Pittolo, Silvia, Lee, Hyojung, Lladó, Anna, Tosi, Sébastien, Bosch, Miquel, Bardia, Lídia, Gómez-Santacana, Xavier, Llebaria, Amadeu, Soriano, Eduardo, Colombelli, Julien, Poskanzer, Kira E., Perea, Gertrudis, Gorostiza, Pau, (2019). Reversible silencing of endogenous receptors in intact brain tissue using two-photon pharmacology Proceedings of the National Academy of Sciences of the United States of America 116, (27), 13680-13689

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

JTD Keywords: Photopharmacology, Photoactivation, Pharmacological selectivity, Functional silencing, 2-photon pharmacology

Tekeli, I., Aujard, I., Trepat, X., Jullien, L., Raya, A., Zalvidea, D., (2016). Long-term in vivo single-cell lineage tracing of deep structures using three-photon activation Light: Science and Applications , 5, (6), e16084

Genetic labeling techniques allow for noninvasive lineage tracing of cells in vivo. Two-photon inducible activators provide spatial resolution for superficial cells, but labeling cells located deep within tissues is precluded by scattering of the far-red illumination required for two-photon photolysis. Three-photon illumination has been shown to overcome the limitations of two-photon microscopy for in vivo imaging of deep structures, but whether it can be used for photoactivation remains to be tested. Here we show, both theoretically and experimentally, that three-photon illumination overcomes scattering problems by combining longer wavelength excitation with high uncaging three-photon cross-section molecules. We prospectively labeled heart muscle cells in zebrafish embryos and found permanent labeling in their progeny in adult animals with negligible tissue damage. This technique allows for a noninvasive genetic manipulation in vivo with spatial, temporal and cell-type specificity, and may have wide applicability in experimental biology.

JTD Keywords: Multi-photon microscopy, Photoactivation, Three-photon microscopy, Zebrafish