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Single Gene Gives Mice Three-Color Vision
maynard writes "A study in the peer-reviewed journal Science shows that mice transgenetically altered with a single human gene are then able to see in full tri-color vision. Mice without this alteration are normally colorblind. The scientists speculate that mammalian brains even from animals that have never evolved color vision are flexible enough to interpret new color-sense information with just the simple addition of new photoreceptors. Such a result is also indicated by a dominant X chromosome mutation that allows for quad-color vision in some women." A sidebar in the article includes a nice illustration of what two-color vs. three-color mice might perceive.
I, for one, welcome our new full-spectrum-observing mice overlords...
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"Such a result is also indicated by a dominant X chromosome mutation that allows for quad-color vision in some women."
Are you kidding me? You know darn well that women can see at least 75 shades of off-white...
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Did they provide gene therapy to the mice which then gained color vision, or did they alter the mice before birth? Is it possible to insert genes into an adult organism and permanently change their DNA structure?
is it possible to genetically alter humans to make them tetrachromats, thus making them able to see UV like fishes and birds do?
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I'm holding out until I can see Squant: http://negativland.com/squant/index.html
One issue I find interesting in this context is the guy who was colour-blind (that is, he couldn't differentiate colours in certain parts of the spectrum). This guy had synesthaesia, and although he couldn't physically see certain colours, he could experience them through his synesthaesia. He referred to them as "Martian colours".
The interesting implication here is that the GM mice's brains apparently developed with the ability to process the new colours. It would be fair to assume that ordinary mice's brains did not even contain the "concept" or "perception" of red hardwired in, since what would the point be?
Thus, if the converse is true, and human brains develop the same way as mice's, it could be assumed that the brains of people with the *physical* inability to detect certain colours from birth would never develop the mental concept/sensation of those colours. (*) But then, now does this explain "Martian colours"?
(*) (If you're having trouble understanding what I mean, try to imagine what ultraviolet "looks" like. Darklight (UV lamp) special effects don't count; that's *visible* light produced when UV hits special fluorescing material. And you can't "cheat" by imagining in terms of false colours (since that, by definition, is *converting* UV to visible-range colours). No, I want you to try to imagine what colour actual UV light would look like... and you'll fail because you've never directly seen UV light, and the concept isn't wired into your brain).
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Most definitly. No color reproduction technology in existence has the capability of reproducing all the colours that the human can experience. (i.e. the Gamut, nice reading in Wikipedia: http://en.wikipedia.org/wiki/Gamut )
Although their GM mouse made M and L type cones in their retinas, it is still not clear if what they reacted to was only a change in intensity, or if they could see a true difference between the two colors. Normal mouse are essentially colorblind in that region of the spectrum, red triggers the M receptor, but not very much, so you need a brighter red light to stimulate the M receptor equally as greenish light. Since you need a very good control, the test setup was such that normal could not see a difference between the red and green light. Their GM mouse were much more sensitive to red, so to them the red light must have had a much brighter intensity. But that does not mean their brains had adapted themselves to differentiating between red and green light. To test that you would have to measure the sensitivity of the new red receptor and adjust your intensity to that so that the only difference is in the color, not the intensity. The problem offcourse is that you cannot do that same experiment with normal mouse which have a different red sensitivity, and no control == bad science.
So their claim that the GMs mouses brain really processed the red light signal different from the green might be a bit over the top.
(hmm thinking about it, if the GM mouse cannot discern between red and green, there might be a certain redlight intensity where their scores would drop significantly, while the controls would score better. If you cannot find that, my hypothesis is wrong and their claim is right. Now lets see if I can find if they did that test...)
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Violet is especially tricky. Its wavelength is shorter than blue, but in addition to stimulating your blue cones, your red cones are also slightly sensitive to it. The camera, however, sees the pure, very deep blue. Then, when it goes to display it on the LCD, it only turns on the blue pixel instead of the blue and a little red.
Another thing that people don't generally notice is that the RGB pixels or phosphors don't match up perfectly with everyone's cones. The only way I can think of to have faithful color representation is to have one "pixel" on both camera and display that is sensitive to and can emit any visible frequency of light, with perfectly flat response. IOW, maybe flying AI-controlled cars will have a camera/display like that.
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The fun part is that even a perfect reproduction of what a human can see would still be only a tiny minority of what is actually there. This is most easily demonstrated with a TV remote and a digicam, which registers the IR light, which the human eye doesn't. Other side effects is that the human eye will register certain very different mixtures of wavelength as the exact same color, while a digicam will register them as two different ones.
We can, if the intensity is high enough.
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A sidebar in the article includes a nice illustration of what two-color vs. three-color mice might perceive.
... thus explaining why mice show no outward tendencies towards jealousy or violence, and behave in a highly cautious manner at all times.
This doesn't make any sense. Red cones are not sensitive to blue light. Here is a diagram showing the sensitivities of of the three cones (S, M, and L or Blue, Green and Red) in our retina whose signals combine to create color.
Our perception of color comes from the combination and comparison of the stimulation of three different cones, each maximally sensitive to different wavelengths. The output of the cones gets combined in what are called opponent pathways, one is Red-Green, and the other is Blue-yellow. The Red-Green pathway compares the output of the Red and Green cones and the Blue-yellow pathway compares the output of the blue cone with the sum of the red and green cones. This is why you will never see a color that is reddish-green or blueish-yellow (see nick) at least in the additive sense that red+blue=violet and yellow+blue+green.
So why does extremely short wavelength light appear to contain a reddish component? I don't believe that anyone knows the answer to that yet. But the hypothesis is that somewhere along the path from cone to cortex the input from a blue cone and red cone combine which turns our perception of an extremely short wavelength light into a combination of short wavelength light (blue) and extremely long wavelength light (red). So our sensation of color becomes a continuum that loops back on itself as opposed to our sense of pitch (which is also frequency or wavelength).
Interestingly people who have had their lenses removed are somewhat able to perceive ultraviolet light. This is because the lens ordinarily blocks UV light and blue cones are sensitive to UV light but very little ever penetrates to the retina normally. Apparently they see it as lilac.
Many mammals, fish, birds, insects, and reptiles (basically everyone except us) are able to see UV light as well. It's a good that we can't for two reason. One is that there is more chromatic aberration at shorter wavelengths. Basically blue light bends more than red light. This makes focusing more difficult. Also, more importantly, UV light damages DNA which is a very, very, bad thing. This is a good resource for learning more.
Yes.
It depends off your target site, but yes it is possible.
- You can replace bone marrow (remove a mutated one that led to cancer, and put another one (given from a relative) that is exempt of the broken gene that lead to the cancer). As you are modifying stem cells (blood cells precursors) the modification is rather permanent. And as the newly produced white blood cells are always re-trained after creation they won't consider your body as foreign so you won't have immune system rejection (graft vs. hosts in this case). And as a bonus, because bone marrow cells have homing capabilities, they're as easy as a blood transfer to inject. But the problem is that, during the time between when you radiated the old marrow to kill the cancer and when the newly injected one has finished recreating white cells, there's a window during which the organism is defenseless against infections.
- Viruses are small things that basically work by injecting their genetic information (DNA or RNA) inside a host cell. Scientist can assemble small virus like things that use the virus shell and thus are able to inject their material, but inside they contain the gene you need to add for the therapy. As far as I've heard there were attempt to use such a system to treat mucoviscidosis (by injecting a gene to help produce working chloride channels). It is administered as a spray. The problems are (beside the high cost of such a method) that the spray only reach the supperficial layer of cells in the bronchus. These are differenciated cells that don't multiply anymore, they only do their work until they die off and fall out. The precursors are deeper and not affected by the therapy. Thus the effects aren't permanent. Plus, after some time the hosts immune system ends up discovering those modified virus and/or infected cells, considers them as foreign and develops antibodies against them. Thus the therapy gets ineffective after some times. Thus the whole idea was scrped and now we mostly use drugs that are cheaper, makes the cells work using the gene they already had before (other ion channels - carbocystein) or directly dilutes the secretions (acetylcystein), and whose effect doesn't diminish with time (thus they are much more effective at reducing the speed of degradations of lungs and buying time before lung transplantation gets necessary).
No. /before/ the brain and the retina gets wired. The colour perception capabilities develops when the nervous fibres grow and connect to different population of receptors.
Transgenic mice = before birth gene modification.
For the mutation to work, it has to happen
You can't 'cure' colour-blindness with gene therapy alone.
Technically speaking, there are virus that can infect retina before birth. But they would be much more difficult and expensive to produce, plus they can have bad side effects, and they are harder to control if they did inject their genes. Also the whole stuff is less ethical for the poor mice. Right now, you modify the mice at the stage of either zygote (1 single cell) or not-yet feconded gamete. You let the zygote do a couple of division, you get one of the dozen cell and check it the gene is still in place. If it is, you implant the stuff in a mother mouse. With the virus way, you have to inject the virus into a mother mouse while she still carries the baby mice (and hope that there won't be too much side effects - inflamation and such - for the mother or the mice she carries), then once the baby mice are born, you have to screen them to see which one carry the new gene (and has them into the eyes. The virus can target several organs, and won't necessarily infect the mice's eyes. I don't know, but maybe removing one of the eyes could be the only solut
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Ducks are pentachromats. They have 5 different receptors for color. That doesn't mean they see other colors than we do, but it does mean they have better color differentiation. I can think of no other explanation other than ducks evolved from artists.
Maybe we can put them to work testing monitors. Your garden variety graphics card and monitor are already capable of producing more colors (4.28 million or some such) than humans can differentiate (3 to 3.5 million).
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If the tetrachromatic mutation affects a single dominant gene in the X chromosome, why is it that it is only expressed phenotypically in females? Men have a single X chromosome too -- in fact, we are more adversely affected by inherited traits such as colour-blindness for the precise reason that we only have a single copy (thus a recessive mutation would be more likely to be manifested, since there's no "normal" version of the gene to suppress it).
Michel
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