Optogenetics

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The optogenetics is a biological technology to be able to control to cellular activity with light. For this purpose, foreign genes are introduced into the target cells, which lead to the expression of light-sensitive ion channels , transporters or enzymes . In a broader sense, fluorescent proteins are also counted among the optogenetic tools that allow cellular activity to be measured with light. The optogenetic control of the activity of nerve cells has already led to numerous new insights into the function of neuronal circuits.

history

Karl Deisseroth and his former colleagues Edward Boyden and Feng Zhang are considered to be leading developers in the field of optogenetics . The decisive breakthrough came with the discovery that light-controlled channels from an alga can be built into cells of other organisms, making them sensitive to light. Georg Nagel and Peter Hegemann published this discovery in 2002 and 2003 and sent their fluorescence-marked genetic tool to the working groups of Karl Deisseroth, Roger Tsien and Alexander Gottschalk. The pioneers of optogenetics avant la lettre also be Gero Miesenböck and Boris Zemelman their research from the years 2002 and 2003 expected. Optogenetics was named Method of the Year 2010 by the journal Nature Methods . The pioneers in optogenetics were awarded the Brain Prize in 2013 .

description

This technology is a combination of methods from optics and genetics , with the aim of activating ( gain-of-function ) or deactivating ( loss-of-function ) certain functional events in specific cells or living tissues . Here, light-sensitive proteins are genetically modified by manipulating the coding DNA (i.e. the corresponding gene) and then introduced into certain target cells or tissue. Under the influence of light it is then possible to control the behavior of the cells modified in this way.

Optogenetics thus allows a targeted and extremely fast (millisecond range) control of precisely defined events in complex biological systems. This enables investigations at the protein level (applications in molecular biology ), at the level of individual cells ( cell biology ) and defined tissues ( histology ) or even at the level of freely moving mammals ( behavioral biology ).

The technology, which was named “Method of the Year 2010” by the scientific journal Nature Methods, is being tested in animal models of Parkinson's and epilepsy .

Optogenetic methods are already used today to identify different intracellular processes, such as B. to research or control the localization of proteins in certain regions of the cell or the production of specific molecules such as second messengers (secondary messenger substances). Through this targeted modification of the cellular signal cascades , cell biology is currently experiencing an increase in knowledge about intracellular processes that was hardly imaginable a few years ago. In neurobiology , too , where the process was first developed, it enables previously unthinkable detailed insights into the functioning of the nervous system and the brain .

Channelrhodopsin as an example of an optogenetic switch

Schematic representation of a ChR2-RFP fusion protein. RFP is a red glowing variant of the green fluorescent protein (GFP).

An example of how optogenetics is used at the molecular level is the use of a genetically modified form of channelrhodopsin (ChR2) as a “switch” molecule. Channelrhodopsins are naturally independent, light-controlled ion channels. Despite their structural similarity, they are not so-called G-protein-coupled receptors . It is now possible to replace or change (modify) the C-terminal end of the ChR2 protein reaching into the intracellular space without the function of the protein as an ion channel being impaired. The genetically modified fusion proteins can then be introduced into excitable cells such as neurons with the aid of a number of transfection techniques (viral transfection , electroporation , gene guns ) and brought to expression (production) there. Vitamin A , the precursor of the light-absorbing chromophore retinal, is usually already present in vertebrate cells, so that excitable cells that express a channelrhodopsin can be depolarized simply by lighting. This in turn allows the use of modified channel rhodopsins, for example for applications such as the photostimulation of neurons. The blue-sensitive ChR2 in combination with the halorhodopsin chloride pump , which can be activated by yellow light, enables neuronal activity to be switched on and off within milliseconds.

If ChR2 is marked with a fluorescent label, axons and synapses excited by light can be identified in intact brain tissue. This technique can be used to elucidate the molecular events during the induction of synaptic plasticity . With the help of ChR2, extensive neuronal pathways in the brain were mapped. It has already been shown for nematodes , fruit flies , zebrafish and mice that the behavior of transgenic animals that express ChR2 in some of their neurons can be controlled without contact by intensive lighting with blue light . A surprising discovery was that targeted mutations can be used to switch the ionic selectivity of ChR2 from cations (Na + , K + ) to anions (Cl - ). Anion-conducting channelrhodopsins are used to suppress neural activity with light.

literature

  • Edward Boyden and T. Knopfel (eds.): Optogenetics: Tools for Controlling and Monitoring Neuronal Activity (= Progress in Brain Research , Volume 196), Elsevier , Amsterdam 2012. (Link to the free first chapter: A comprehensive concept of optogenetics )
  • [1] The Brain Prize 2013 jointly awarded to Ernst Bamberg, Edward Boyden, Karl Deisseroth, Peter Hegemann, Gero Miesenböck and Georg Nagel for '… their invention and refinement of optogenetics. ... '
  • Optogenetics - Opportunities in Application, BT-Drs. 19/9084

Individual evidence

  1. ^ Lief Fenno, Ofer Yizhar, Karl Deisseroth: The Development and Application of Optogenetics . In: Annual Review of Neuroscience . tape 34 , no. 1 , July 21, 2011, ISSN  0147-006X , p. 389-412 , doi : 10.1146 / annurev-neuro-061010-113817 , PMID 21692661 , PMC 6699620 (free full text) - ( annualreviews.org [accessed February 5, 2020]).
  2. ↑ Kerri Smith: Method man: Karl Deisseroth is leaving his mark on brain science one technique at a time , in: Nature , Volume 497 of May 30, 2013, p. 550.
  3. ↑ Millisecond timescale, genetically targeted optical control of neural activity. Nat Neurosci 8, 1263-1268 (2005). Boyden, ES, Zhang, F., Bamberg, E., Nagel, G. & Deisseroth, K. Nat Neurosci 8, 1263-1268 (2005).
  4. ↑ Kerry Grens: Feng Zhang: The Midas of Methods . in: The Scientist Magazine .
  5. Jump up ↑ Georg Nagel, Doris Ollig, Markus Fuhrmann, Suneel Kateriya, Anna Maria Musti, Ernst Bamberg, Peter Hegemann: Channelrhodopsin-1: A Light-Gated Proton Channel in Green Algae . In: Science . tape 296 , no. 5577 , June 28, 2002, ISSN  0036-8075 , p. 2395–2398 , doi : 10.1126 / science.1072068 , PMID 12089443 ( sciencemag.org [accessed August 18, 2017]).
  6. ↑ Georg Nagel, Tanjef Szellas, Wolfram Huhn, Suneel Kateriya, Nona Adeishvili, Peter Berthold, Doris Ollig, Peter Hegemann, Ernst Bamberg: Channelrhodopsin-2, a directly light-gated cation-selective membrane channel . In: Proceedings of the National Academy of Sciences . tape 100 , no. 24 , November 25, 2003, ISSN  0027-8424 , p. 13940-13945 , doi : 10.1073 / pnas.1936192100 , PMID 14615590 ( pnas.org [accessed August 18, 2017]).
  7. ^ Georg Nagel, Martin Brauner, Jana F. Liewald, Nona Adeishvili, Ernst Bamberg, Alexander Gottschalk: Light Activation of Channelrhodopsin-2 in Excitable Cells of Caenorhabditis elegans Triggers Rapid Behavioral Responses . In: Current Biology . tape 15 , no. 24 , p. 2279–2284 , doi : 10.1016 / j.cub.2005.11.032 ( elsevier.com [accessed August 18, 2017]).
  8. ↑ Boris V. Zemelman, Georgia A. Lee, Minna Ng and Gero Miesenböck: Selective Photostimulation of Genetically ChARGed Neurons , in: Neuron , Volume 33, No. 1 of January 3, 2002, pp. 15-22.
  9. ↑ Boris V. Zemelman, Nasri Nesnan, Georgia A. Lee and Gero Miesenböck: Photochemical gating of heterologous ion channels: Remote control over genetically designated populations of neurons , in: PNAS , Volume 100, No. 3 (2003), p. 1352 -1357.
  10. ^ Lief Fenno, Ofer Yizhar and Karl Deisseroth: The Development and Application of Optogenetics , in: Annual Review of Neuroscience , Volume 34 (2011), pp. 389-412, here pp. 390f.
  11. ↑ Anonymous: Method of the Year 2010. In: Nature Methods. 8, 2010, pp. 1–1, doi: 10.1038 / nmeth.f.321 .
  12. ^ A b Karl Deisseroth : Optogenetics . In: Nature Methods . tape 8 , no. 1 , 2011, p. 26-29 , doi : 10.1038 / nmeth.f.324 , PMID 21191368 .
  13. ↑ a b In the light of the cells . Time online . Retrieved January 26, 2011.
  14. ↑ Special Feature: Method of the Year 2010 . Nature. Retrieved January 26, 2011.
  15. ↑ Jared E Toettcher, Christopher A Voigt, Orion D Weiner, Wendell A Lim: The promise of optogenetics in cell biology: interrogating molecular circuits in space and time . In: Nature Methods . tape 8 , no. 1 , 2011, p. 35-38 , doi : 10.1038 / nmeth.f.326 , PMID 21191368 .
  16. ↑ Silvana Konermann , Mark D. Brigham a. a .: Optical control of mammalian endogenous transcription and epigenetic states. In: Nature. 2013, S., doi: 10.1038 / nature12466 .
  17. ↑ Feng Zhang , Li-Ping Wang, Martin Brauner, Jana F. Liewald, Kenneth Kay, Natalie Watzke, Phillip G. Wood, Ernst Bamberg , Georg Nagel, Alexander Gottschalk, Karl Deisseroth : Multimodal fast optical interrogation of neural circuitry . In: Nature . tape 446 , no. 7136 , March 5, 2007, p. 633-639 , doi : 10.1038 / nature05744 , PMID 17410168 .
  18. ^ Yan-Ping Zhang, Thomas G Oertner: Optical induction of synaptic plasticity using a light-sensitive channel . In: Nat Meth . tape 4 , no. 2 , January 2007, p. 139-141 , doi : 10.1038 / nmeth988 , PMID 17195846 .
  19. ↑ Yan-Ping Zhang, Niklaus Holbro, Thomas G. Oertner: Optical induction of plasticity at single synapses reveals input-specific accumulation of αCaMKII . In: Proceedings of the National Academy of Sciences . tape 105 , no. 33 , 2008, p. 12039-12044 , doi : 10.1073 / pnas.0802940105 , PMID 18697934 .
  20. ↑ Leopoldo Petreanu, Daniel Huber, Aleksander Sobczyk, Karel Svoboda: Channelrhodopsin-2-assisted circuit mapping of long-range callosal projections . In: Nat Neurosci . tape 10 , no. 5 , April 15, 2007, p. 663-668 , doi : 10.1038 / nn1891 , PMID 17435752 .
  21. Jump up ↑ Adam D. Douglass, Sebastian Kraves, Karl Deisseroth , Alexander F. Schier, Florian Engert: Escape Behavior Elicited by Single, Channelrhodopsin-2-Evoked Spikes in Zebrafish Somatosensory Neurons . In: Current Biology . tape 18 , no. 15 , July 5, 2008, p. 1133-1137 , doi : 10.1016 / j.cub.2008.06.077 , PMID 18682213 .
  22. ↑ Daniel Huber, Leopoldo Petreanu, Nima Ghitani, Sachin Ranade, Tomas Hromadka, Zach Mainen, Karel Svoboda: Sparse optical microstimulation in barrel cortex drives learned behavior in freely moving mice . In: Nature . tape 451 , no. 7174 , January 3, 2008, p. 61-64 , doi : 10.1038 / nature06445 , PMID 18094685 .
  23. ↑ J. Wietek, JS Wiegert, N. Adeishvili, F. Schneider, H. Watanabe: Conversion of Channelrhodopsin into a Light-Gated Chloride Channel . In: Science . tape 344 , no. 6182 , April 25, 2014, ISSN  0036-8075 , p. 409-412 , doi : 10.1126 / science.1249375 ( sciencemag.org [accessed February 5, 2020]).
  24. ↑ Jonas Wietek, Riccardo Beltramo, Massimo Scanziani, Peter Hegemann, Thomas G. Oertner: An improved chloride-conducting channelrhodopsin for light-induced inhibition of neuronal activity in vivo . In: Scientific Reports . tape 5 , no. 1 , October 7, 2015, ISSN  2045-2322 , doi : 10.1038 / srep14807 .
  25. ^ Naoya Takahashi, Thomas G. Oertner, Peter Hegemann, Matthew E. Larkum: Active cortical dendrites modulate perception . In: Science . tape 354 , no. 6319 , December 23, 2016, ISSN  0036-8075 , p. 1587–1590 , doi : 10.1126 / science.aah6066 ( sciencemag.org [accessed February 5, 2020]).

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