Class notes

Cellular Neurophysiology (NEUR0007) Notes - Optogenetics

0 purchase

Course
Cellular Neurophysiology (NEUR0007)

Institution
University College London (UCL)

Explore Cellular Neurophysiology at UCL with a focus on Optogenetics. Delve into the transformative world of manipulating neural activity with light. Please note that these materials are intended for personal use only and should be used in accordance with academic integrity guidelines.

[Show more]

Preview 2 out of 10 pages

View example

Uploaded on December 1, 2023
Number of pages 10
Written in 2021/2022
Type Class notes
Professor(s) Dr martin stocker
Contains All classes

optogenetics

Institution
University College London (UCL)
Education Unknown
Course
Cellular Neurophysiology (NEUR0007)

sujansathiendran

Member since 3 year 5 documents sold

$8.43

Add to cart

Add to wishlist

100% satisfaction guarantee
Immediately available after payment
Both online and in PDF
No strings attached

Optogenetics
Optogenetics
 Optogenetics
o A technique that revolves around expressing light receptors in cells of interest – such that you can
control the activity of those cells by shining light on them
 Allows precise control (activation or inhibition) of cells of interest – in a temporally precise
manner
 Tool for manipulating brain functions
o An approach which allows the control of neuronal activity with light
o A combination of optical and genetic techniques
 Opto
 Delivery of light to neurons expressing light-sensitive ions channels/pumps or GPCRs
 Genetics
 Targeting of specific neurons with genes encoding for light-sensitive ion
channels/pumps or GPCRs
 Development of optogenetics
o In algae – channelrhodopsins function as visual proteins directing the algae towards or away from a
light source, or to find light conditions that are optimal for photosynthetic growth
 Channelrhodopsins
 A subfamily of retinylidene proteins that function as light-gated ion channels
 Serve as sensory photo-receptors in unicellular green algae – controlling phototaxis =
movement in response to light
o ChR2 = channelrhodopsin 2
 Binds to all-trans retinal  causes conformational
change when retinal absorbs light forming 13-cis
retinal  conformational change drives gating of ion
channels  allowing entry of positively charged ions
 Light absorption triggers subsequent
conformational change of the protein +
gating of the channel
o YFP-ChR2 fusion protein
 If YFP is attached to ChR2 = label – any cell
expressing ChR2 glows = allows easy detection of
cells expressing channel rhodopsin
o ChR2 with reduced desensitisation characteristics
 Responds to light in a more sustained fashion than ChR2
 Optogenetic control of firing in vitro
o Boyden et al – investigated whether ChR2 could be used to control activity of neurons
 Neurons grown in culture were transduced with ChR2-YFP fusion protein
 Patched cultured neurons – held in voltage clamp
 Applied blue light to neurons  resulted in strong inward current =
strong depolarising current
 Patch cultured neurons – in current clamp mode
 Pulses of blue light 10ms or longer was sufficient to induce
action potentials
 Optogenetic control of firing ex vivo
o Developed a viral construct which could be used to deliver ChR2 into mice
o Viral construct was infused into the hippocampi of adult mice
 ChR2 was under the control of the EF-1α promotor – with YFP as a reporter
 ChR2 was expressed in the adult mouse hippocampus
o Made slices from hippocampi

, Optogenetics
 In voltage-clamp – blue light resulted in strong depolarising current
 In current clamp – brief pulses of blue light could reliably drive spiking in the neurons
 Optogenetic control of firing in vivo
o Developed transgenic mouse line which expressed ChR2 in cortical neurons
o Simultaneously made electrophysiological recordings from the cortex while they applied blue light
via a fibre optic cable
 Showed that application of blue light could reliably drive spiking in recorded neurons in the
cortex
 Spiking could be precisely timed with short pulses of blue light
 Temporal and spatial precision
o Optogenetics allows ability to target it such that one can make temporally and spatially
manipulations of neuronal activity
 Not possible with other stimulation techniques – electrical or pharmacological
o 1
 Physical delivery of virus to a given anatomical location by syringe
 Only cells within vicinity of injection site will take up optogenetic gene and express it
 Deliver light to injection site  causes selective activation in injection site
 Uncovers circuit connectivity patterns by making use of axonal projections
o Increase selectivity by activating neurons expressing optogenetic construct
based on their axonal projections
 By moving light to a different structure – only activates neurons
which project to this particular structure
 Selects a subset of neurons within injection – activating a
specific pathway
o 2
 Or genetically target neurons to be activated
 Cell types can be addressed if the cell type of interest has a known genetic identity
o E.g. target to hippocampus  use genetic techniques to make sure channel
rhodopsin is only expressed in a particular subset of cells or subtype of cells
o 3
 Precision of illumination
 Use lasers to individually target illumination to specific cells
 Directing the illumination source to a given set of cells or even individual neurons –
useful when the targets of interest are separated in space
 Delivering the genetic construct
o Optogenetic constructs are delivered to target cells via a virus
o Stages
 Piece together genetic construct (transgene)
 Promotor to drive gene expression + gene encoding opsin (light-sensitive ion
channel) + fluorescent reporter


 Package construct into virus
 Adeno-associated virus (AAV) is a small virus which can be used as a
vector to deliver target genes into mammals
o On its own, AAV is biologically inert = no chance of causing
infection or disease + non-replicating

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller sujansathiendran. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $8.43. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

69252 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 15 years now

Start selling

Class notes

Cellular Neurophysiology (NEUR0007) Notes - Optogenetics

Document information

Subjects

Written for

Seller

Reviews received

Content preview