1. 1st Breaking Video
IT_Pro
27/11/2018
Optogenetics

2. Consolato Sergi, M.D., Ph.D. University of Alberta Hospital
Optogenetics
Consolato Sergi, M.D., Ph.D.
University of Alberta Hospital
27/11/2018
Optogenetics

3. 2nd Video - Optogenetics
Optogenetics_ Controlling the brain with light?
27/11/2018
Optogenetics

4. Signals Single-electrode recordings - Limitations
- Intracellular recordings: Only a few neurons and difficult in vivo - Extracellular recordings: No capture information about sub- threshold activity, bias against small cells, poorly defined cell identities
2-deoxyglucose (2DG) imaging (H3 or C14) - Limitations
- Visualization of active brain areas or neurons (post-mortem) - Temporal resolution in min or hrs, not msec. - ‘One-shot’ or ‘two-shot’ ways.
PET/fMRI: poor spatio-temporal resolution, hemodynamic transformation, drug receptor activation patterns.
Optical Intrinsic Signal Imaging (OISI): hemodynamic response in local capillaries related to local activity.
Voltage Sensitive Dye Imaging (VSDI): membrane voltage, mostly sub-threshold activity in neurones and glia cells.
27/11/2018
Optogenetics

5. Optogenetics should allow
fast depolarization / hyperpolarization of specific cells in living animals
precise control and study of cell population dynamics
the identification of causal positive and negative proof with cell specificity
superior targeting & biocompatibility vs. electrical stimulation
visual confirmation of target morphology using fluorescent labeling
27/11/2018
Optogenetics

6. Channelrhodopsin-2 (ChR2) Light-activated non-selective cation channel
Chlamydomonas reinhardtii- Wikipedia
Zhang F, Wang L-P, Boyden ES and Deisseroth K (2006) Channelrhodopsin-2 and optical control of excitable cells. Nature Methods 3(10): 785–792.
Channelrhodopsin-2 (ChR2)
Light-activated non-selective cation channel
Alga: Chlamydomonas reinhardtii
Requires all-trans retinal (ATR), which is present in mammals
50 fS per channel -> 0.1–1M ChR2 molecules are required to achieve 1 nA
27/11/2018
Optogenetics

7. Light-activated chloride pump Archaebacterium Natronomas pharaonis
Zhang et al (2007) Multimodal fast optical interrogation of neural circuitry. Nature 446: 633–641.
Archaea –
Wikipedia
Halorhodopsin (NpHR)
Light-activated chloride pump
Archaebacterium Natronomas pharaonis
/- 27 nm
Inactivates after ~1 sec
27/11/2018
Optogenetics

8. Current Status of Applications
Some published work in animals (e.g. mouse & zebrafish):
Control and mapping of the function of motor cortex
Expression restores light responses in retinal ganglion cells
Dissection of Parkinson’s circuitry
Dissection of role of DA neurons in behavioral conditioning
Temporally precise in vivo control of intracellular signaling
Potential control of epileptiform activity
High-speed mapping of synaptic connectivity
Dissection of a behavioral module in the spinal cord
27/11/2018
Optogenetics

9. ...but how much is there to be discovered?
Take Home Message
Optogenetics is Nature Method of the Year 2010 and is going to have more biology applications in the future!!!
...but how much is there to be discovered?
…is it up to us?
More Information on Pub Med and on website of Dr. Chou Hung, Ph.D. vision.ym.edu.tw/courses/methods/Presenta tion2.ppt
Thank you
27/11/2018
Optogenetics