Bio club bulletin first issue : optogenetics
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Transcript of Bio club bulletin first issue : optogenetics
Biology
Club 2013-2014
Dec 2013 Bulletin Issue #1 Optogenetics
• What are optogenetics?
• Optogenetics and you
Read on to discover
more!:)
Inside:
Have you ever heard about “光遺傳學”???
Optogenetics (光遺傳學) is the science of using light to
stimulate certain responses from cells, groups of cells or
organs within complex biological systems.
Neuroscientists
traditionally study the
function of the brain by
stimulating and
recording the activity of
single nerve cells with
electrodes. The idea of
using light to start or
stop neurons in living animals was proposed some decades ago by the
famous Nobel Prize–winning scientist, Francis Crick. The optogenetic
method was pioneered in 2005 by Boyden and Karl Deisseroth at
Stanford University.
However, what is optogenetics exactly?
Optogenetics is the combination of genetics and optics to control
well-defined events within specific cells of living tissue. It includes the
discovery and insertion into cells of genes that confer light
responsiveness; it also includes the associated technologies for delivering
light deep into organisms as complex as freely moving mammals, for
targeting light-sensitivity to cells of interest, and for assessing specific
readouts, or effects, of this optical control. Both precision in the length
What is Optogenetics?
INTRODUCTION:
of the bursts of light and the
ability to produce bursts of
light with great speed are
essential to the practice of
optogenetics.
Optogenetics involves the use of light to provoke responses from
certain proteins existing as part of complex biological systems. It can also
involve the use of light to invoke responses from single cells, rather than
groups of cells.
READ MORE, KNOW MORE and
LEARN MORE
Continual reading…… Find out more
about the OPTOGENETICS ~~~~~
Over the years, scientists have been trying hard to understand
how our brains work.
However, with limited technology, we human only knew a small
part of this mystery.
In 2002, some scientists discovered a protein that can cause
green algae to move towards or away from light. They later
found out that the protein (channelrhodopsin2 or ChR) is a light
sensitive channel. Blue light causes the channel to open and
enables ion to float in, which activate the nerve cell, while
when given no light, the channel will be closed. They saw the
potential of it and wondered if the protein can control the
movement of the algae with light,
if they get the protein into the
nerve cell, they can control the
nerve activities in the brain.
In August 2005, Ed Boyden and Feng Zhang have successfully
tried the technology on mammal nerve system. The most
famous example is the optogenetic were used to
control the eyes’ behavior of a monkey. With
inserting a certain ChR, when the blue light is on,
the monkey eyed on the target faster than usual.
In 2006 the word “optogentic” was even coined!
This discovery has been a huge
milestone for mankind. It has
made us easier to understand our
brain and even will be able to cure
Parkinson’s disease or other
metal illness. For your information, it hasn’t been used in a dark
evil way like what you see in the movies, humans are not
DOOMED, please don’t worry.
Living things responding to light?! So strange…
Actually, living organisms with phototropic response are everywhere! For
example plants, which usually grows towards the light.
And of course we humans, where the light-sensitive cell on the retina of
our eyes detect light.
So you are now more familiar with phototropic response, but how does
it work? In most cases, it involves light-sensitive proteins, which change
their chemical structures when exposed to light.
Let me introduce you a protein which plays a significant role in
Optogenetics, the Channelrhodopsin
It is a channel protein which opens to ion transportation when exposed
to blue light
So now we are using this kind of proteins to control biological process.
Let’s have a case study. Mammals’ brains are
made of neurons, or also called nerve cells.
They send electrical pulses to control the body
or when the organism is thinking.
We insert these light-sensitive proteins into the
brain of a mouse. And when light hits the
channel rhodopsin gene, the excited nerve cell
carries out ion transportation and sends out
electrical pulses, which in turn affects the
behaviour of the mouse.
First of all, doctors are required to drill holes in people’s skulls to
carry out the surgery. It also involves changing the DNA of brain cells
unreliable and unpredictable, risky
optogenetics become more unfavorable.
Fiber optics could pose the threat of
infection and being uncomfortable and
having to carry heavy batteries
Optogenetics requires high tech work
and specific knowledge to let the whole
thing work.
extremely expensive
+ May reserved for the wealthy ones but
not ordinary people
+ Only a small number of people in the
society will be able to enjoy this new technology, optogenetics is not the
significantly great if it is not able to benefit the whole society.
Moreover, to let optogenetics to become efficient, specific knowledge
about the illnesses’ neural underpinning is needed. Unfortunately, this
kind of specific knowledge is one of the most important missing puzzle
pieces to let us solve major mental illness like depression.
Therefore, we can conclude that without the knowledge about the
illnesses’ neural underpinning, we cannot use this new technique. There
are still quite a number of unsolved question in this field too.
Cell culture, Network analysis
The optogenetic method provides new opportunities to analyze neural
networks. This can be achieved by growing cultured nerve cells on micro
or nano patterned substrates. Cells can be stimulated or silenced simply
by a light-beam with up to now unknown spatial precision. Only for
registration of the light evoked signals electrodes devices are necessary.
Results from these experiments are expected to be used for theoretical
work on neural nets.
Mapping of the brain and behavior
Immediately after having demonstrated that ChR2 can be used for
remote control of neurons, many laboratories started projects for the
mapping of the brain in living animals. Excellent work by various groups
shows, that the application of the optogenetic methods opens the door
in the near future for more detailed studies, which have not been
possible with the traditional electrical and optical methods. To name
some examples; studies are possible on which certain areas of the brain
are stimulated via light pipes. Results are obtained on the movement of
whisker of rodents; on the olfactory system where light replaces the
ligands, and on the movement of animals after stimulation of the motor
cortex.
Gene therapy
In the future gene therapy with the optogenetic tools appears possible.
Transduction via Adeno Associated Viruses (AAV) has been performed
successfully on the human eye to cure Lebers Congenital Amaurosis, by
transduction of cells in the human retina to replace the missing retinal
isomerase. In analogy to this, AAV´s could be loaded with the microbial
rhodopsins and could be used for gene therapy on the diseases listed
below.
What’s so good about optogenetics?
Recovery of vision
Experiments on photoreceptor deficient mice have shown that light
evokes potentials in the visual cortex after the transduction of the ON
bipolar cells with ChR2 in the retina. This indicates that the retina of the
animals regained photosensitivity, which is transmitted via the optic
nerve to the brain. Trajectories of the movement of the animals in the
dark and in the light show clearly an increased activity in the light as it is
obtained for wild type animals. It is conceivable that such an approach
might be possible for blind humans, suffering e.g. the dry or the
wet maculardegeneration. However, in order to come to this point many
biomedical, biophysical and technical hurdles have to be surmounted.
This would be an alternative to the technology, which implants
photosensitive chips in the human eye, which is far away from a
satisfying treatment.
Parkinson disease, Epilepsy
Besides the application of drugs Parkinson disease (PD) can be treated
by Deep Brain Stimulation (DBS). The method consists of the stereotactic
application of a metallic bipolar or quadrupole electrode to the nucleus
subthalamicus within the brain. With help of the electrodes an
oscillating electric field is applied stimulating the neuronal cells. With
this approach spectacular results are obtained, which represent a
substantial improvement compared to the drug therapy. Because of the
geometry of the electrodes a precision of about one millimeter can be
achieved. The extracellular stimulation by the electrodes induces not
only the required depolarization of cells, but also partially a
hyperpolarization, which inactivates cells with unwanted side effects.
This means that parts of the target area are not under perfect control.
The optogenetic method is completely different. If successful this
approach will lead to an improved treatment of PD: Virus induced
transduction of cells with ChR2 allows the activation of the target
structure in the brain via appropriate light sources without the side
effects. As discussed above the advantages are the cell specificity, high
temporal and spatial resolution in the micrometer range, which would
open ways for the stimulation of substructures of the nucleus
subthalamicus. The latter would give the chance to get a deeper
understanding of the cause of this disease.
With respect to Epilepsy similar arguments would hold, because here
certain areas in the cortex are affected. One could speculate that
optogenetics would attract focus also to other diseases including
neuropsychiatric diseases.
To summarize, optogenetics offers great opportunities to for basic
research in the neurosciences, as already has been demonstrated by
many laboratories worldwide. The biomedical applications, however,
hold unpredictable challenges and risks.
Stay tuned for more bio club’s
activities!!!!
Crosswords!!
E Q M E M R S I N Y B V B X U
E T A G E K G S S K S F I R D
C H L B U L C E H T N I O J U
N G S I J Z S G N B X N L S F
E I R W Y V N M R E E W O L I
I L M V C I R R C R L B G L Y
C E K P K O O U V X B G Y E A
S K Q A F E S E E H C S Y C L
O B M S C I T E N E G O T P O
R B N F M W N K C P K P U A H
U Y I G P S Y G E V S U E G N
E R S C L B W S B V O A F N C
N L Z M S C H O W A N L J A B
U B X R J K M H N E S S V R W
A G D M N E T S K G G M J T W
OPTOGENETICS, BIOLOGY, NERVE, CELLS,
NEUROSCIENCE, LIGHT, MSCHOW, MSLEE, MRSIN,
MRSLAM, MSWONG, MSLAU, CHEESE, MAKING,
JOINTHECLUB, GENE
,
Further reading:
http://www.youtube.com/watch?v=I64X7vHSHOE
http://faculty.washington.edu/chudler/opto.html
http://www.optogenetics.co.uk/index.html
http://www.united-academics.org/magazine/mind-brain/new-mri-techniques-what-i
s-brain-mapping-and-how-does-it-work-optogenetics-mit/
BIOLOGY CLUB BULLETIN TEAM: 5A (6) Anson Lam
4I (7) Justin Leung
3B (21) Shum Wing Zi
3F (27) Wu Jenny
4B (7) Mak Siu Hin
4B (13) Chan Cheuk Ki