basic idea about optogenetics, photobiology and ift biology and how they are inter-related to each other.

1. Optogenetics, Photobiology,
and IFT-biology
Presented by - Ravi Ranjan

2. Optogenetics

3. Previous works

4. optogenetics
• Science of using light and light sensitive proteins into cells and its
application.
• Use of light to control cells in living tissue, that have been genetically
modified to express light-sensitive ion channels and monitor the
activities of individual neurons in living tissue.

5. How it all started?
• Some microorganisms produce visible light gated proteins, which direcly regulate
the flow of ions across plasma membrane. Bacteriorhodopsin being activated by
visible light photons.(Stoeckenius and Oesterhelt, 1971;)
• Response of Chlamydomonas reinhardtii in presence of light, protein that cause
green algae to swim towards or away from light is a light sensitive channel .
• Blue light causes the Channelrhodopsin to Open and +ve ions flood into cells and
cause nerve cell to activate.(Hagemann, Negal et al.,2002;)
• Similarly, use of Halorhodopsin from Natrosomonas pharonis to switch neurons
off in presence of yellow/orange light.(Matsuno-yagi and /mukhota,1977;)

6. response of Chlamydomonas reinhardtii in absence and presence of light

7. Opening of ChannelRhodopsin2 in presence of blue light
and generation of nerve impulse. ( Curtsy-
https://www.ncbi.nlm.nih.gov/pubmed/.)
Opening and Halorhodopsin in presence of
yellow/orange light.

10. Applications
• Optical stimulation of electrically excitable cells can be performed
simply by light with high precision.
• Targeting control tools to cells of interest and obtaining compatible
readouts, and analysis of activities.
• It can be used to study neurons involved in Epilepsy, Visual
impairment, Anxiety, Schizophrenia, Parkinson’s disease and several
other neurodegenerative diseases and may lead to a new treatment
method.

11. Photobiology
• Study of the interaction of light and the living organisms.
• Sunlight is the most important element of our environment, since it is
the ultimate source of energy.
• Most of the energy from the sun reaches Earth in the form of
• Visible light
• Infrared radiation
• A small amount of ultraviolet radiation
• Organism interact with a particular range of the wavelength of light.

12. Light strikes the earth in rays of varying wavelengths.
 Long rays (infrared) are unseen but felt as heat.
 Intermediate length rays are visible as light.
 Shorter rays (ultraviolet) are also invisible

13. Properties
Infrared Visible Ultra-violet
Wavelengths longer than red light The different colors of light make
up the visible spectrum.
Wave lengths shorter than violet
light
It can be felt as heat Red has the longest wave length Can cause eye problems
Used to warm food Violet has the shortest wave length Can cause skin damage

14. • There are various role of light in biological system :-
 Photosynthesis
 Photo morphogenesis
 Visual processing
 Photopriodism

15. Photoreceptors:
• In cell biology:
• Photoreceptor cell, a photosensitive cells(rod and cone) in the retina of vertebrate
eyes.
• Microbial photoreceptor, the photoreceptor organelle of a unicellular organism that
allows for phototaxis.
• In biochemistry:
• Photoreceptor protein, a chromoprotein that responds to being exposed to a certain
wavelength of light by initiating a signal transduction cascade.
• Photopigment, an unstable pigment that undergoes a physical or chemical change
upon absorbing a particular wavelength of light.
• In technology:
• Photodetector or photosensor, a device that detects light by capturing photons.
• Electronic photoreceptor, a sensor that converts solar energy into electric energy.

16. Photoreceptor cells
• A photoreceptor cell is a specialized type
of neuron found in the retina that is capable
of phototransduction.
• There are currently three known types of
photoreceptor cells in mammalian
eyes: rods, cones, and photosensitive retinal
ganglion cells.
• Rod and cone cells contribute to visual
system.

17. Differences between rod and cone cells.

18. Photoreceptor proteins
Six well-characterized photoreceptor families function in Nature to
mediate light-induced signal transduction: the Rhodopsins,
phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF
proteins.
Rhodopsins Ion channel protein
Phytochromes Photopriodism
Xanthopsins Carries trans-coumaric acid(a chromophore)
Cryptochromes Flavin-based, opening of stomata
Phototropins Flavin-based, UV A/ blue light receptor
BLUF Flavin-based, present in PAC.
Source: http://pubs.acs.org/doi/abs/10.1021/ar020219d

19. Properties of photoreceptors
• Each photoreceptors exhibits absorption of different spectra.
• Response depends upon-
• No. of photon (rod cells needs less than cones).
• Wavelength of light (colour and range for activation of photoreceptors).
• Time of exposer to light .

20. Intraflagellar Transport
• Eukaryotic cilia and flagella, including primary cilia and sensory cilia, are highly conserved
organelles that project from the surfaces of many cells. The assembly and maintenance of these
nearly ubiquitous structures are dependent on a transport system, known as ‘Intraflagellar
transport' (IFT).
• The bi-directional Movement of non-membrane-bound particles from the cell body out to the tip
of the cilium or flagellum, and then returns them to the cell body.
• The IFT particles are composed of about 20 proteins organized in two subcomplexes called
complex A and B.
• IFT particles along the microtubule is carried out by two different microtubule-based motors, the
anterograde motor is heterotrimeric kinesin-2, and the retrograde motor is dynein 1b.
Source: Rosenbaum JL1, Witman GB. Nat Rev Mol Cell Biol. 2002 Nov;

21. Source: https://en.wikipedia.org/wiki/Intraflagellar_transport

22.  IFT has been best characterized in the biflagellate
alga Chlamydomonas reinhardtii as well as the sensory
cilia of the Caenorhabditis elegans.

23. Importance of IFT
• IFT machinery has now been implicated in many disease phenotypes generally
associated with non-functional (or absent) cilia.
• Diverse group of genetic syndromes and genetic diseases are understood to arise
due to malfunctioning cilia, and the term "ciliopathy" is now used to indicate
their common origin. (Ex- retinal degeneration, situs inversus, liver disease).
• These and possibly many more disorders may be better understood via study of
IFT.
• IFT has its potential role in signal transduction. IFT has been shown to be
necessary for the movement of signaling proteins within the cilia, and therefore
may play a role in many different signaling pathways.

24. Thank you