Sensory Substitution with Optogenetics

Has anyone looked into using optogenetics as a method for sensory substitution ?

Vector I found seemed to be an adenovirus variant and has a low immune response in a rat model, unsure about humans though...

If we could localize a red-shifted therapy to a small location of sensory neurons in the skin?


  • edited July 2014
    Barring the fact I don't think any grinders could easily get their hands on any of the material needed for optogenetics (not to mention that while I think we're all adventurous, trying out untested adenoviruses on ourselves is reckless bordering on stupid), I'm not sure what you mean by red-shifted therapy. Don't optogenetics usually need ChR2, meaning it's blue light?
  • Do you think I could get away with transplanting grown opto cells rather than injecting the AAV? 

    Also, if it was replication deficient then I don't see too much harm in a small localized injection, but I'm not sure how to keep it localized.

    @mothball: Last I heard they can use a lot of types of light, some of which can penetrate the skin.
  • edited August 2014
    I'm unsure how transplanting would work, and if they'd attach to neural endings on their own. A treated skin graft might be possible but you'd need a way to repair nerve damage.

    There is 3 mechanoreceptors that look interesting - Merkel Cells, Meissner corpuscles & Ruffini endings. The first two are involved in "light touch" and the latter in sensing stretch. They are interesting because they are very close to the surface and don't seem to be involved in registering pain.

    I've been looking at Merkel cells since there is already promising lab research with transgenic rats.

    I think replication deficient viral vectors are far easier &
    more promising, since making this thread, I've been working on some
    draft viral vectors that utilize chETA (fast stimuli, 200Hz) and currently looking at Cck & Math1 promoters. When I'm happy with them will release to community.

    I'm currently looking for an ideal place to place - according the Atlas of Sensory Organs; "The density of Merkel cells per innervating sensory neuron ranges from 2 to 5 (vibrissae), through 4 to 16 (glabrous skin of fingertips), to 40 to 50 (hairy skin of forearm)."

    There is supposed to be roughly 150-750 Merkel cells per sq. cm in the finger tips, so I thought maybe the forearm might be ideal. But then later the same books states "Hairy skin is characterized by a low density of touch receptors (all five described types occur), large receptive field (d = 40–50 mm) and a resolution (two-point limen, the minimal separation between two points that permits both to be perceived) of 40–50 mm. Conversely, the glabrous skin of fingertips has a much higher density of receptors (one Merkel cell and two Meissner’s corpuscles/mm2), yielding a receptive field of 3.7–4.0 mm diameter."

    So in one paragraph it suggest the forearm could be more denser than fingertips, then suggests that hairy skin is less dense..

    It also states; "Meissner’s corpuscles would be better suited for a precise tactile mapping of objects than are Merkel cells; however, they lack the information pertaining to static parameters. The Braille script with its pattern of raised dots is an ideal object for Meissner’s corpuscles, although the Merkel system is also required for the evaluation of the height of dots and the pressure on fingertips"

    "Merkel cells only detect edges of 8 μm and above, and for an optimum response the surface marking must be a corner (pivot point of deformation) rather than an edge."

    So it sounds like the absolute ceiling resolution would be 125 per mm (8/1000), but it'll much less than that.

    I also purchased a smart watch (gear 2 neo) and have got a POC app on it.

    Mothball is right, yes ChR2 requires blue light, you can also use red light for deeper penetration (something like ReaChR), and there is other expression vectors for utilizing other light wavelengths.

    and yes these are adeno-associated viruses, (not straight up adenoviruses) which have typically a very low immune response in mammals. I agree, I will probably see if I can try these on lab models first. Materials is not an issue.

    Ah one thing I forgot to mention, is that might need to develop a temporary soluton to turning off the Piezo2 expression (the way these cells feel normally) - so will have to create an Antisense tech for this as well.
  • Here's some pics of the smart watch & app


    and a rough example of it being worn


  • Hello,

    Can I rephrase the question: has anyone here yet attempted, on himself or any human subject, optogenetics in any form? :O I thought i's a thing of distant future but I can already see there are some clinical trials being done apparently...

    I might even have some contacts with access to viral vectors, however, would I have any chance of convincing them to inject those into myself? What are possible risks of using vectors that were proven with rats, or etc?

    Transfecting touch receptors seems like kind of a waste for something that could make a spectacular neural interface. Would it be possible, as a most basic experiment, to locally transfect some irrelevant nerve branch and see if it responds to light?

    jarradhope: is your intention to use a smart watch as a stimulation source? Do you already have access and experience with optogenetics? If you do I would really like to learn more about current status of this technology.

  • edited August 2014
    This isn't like sticking magnets in your fingers, I'm not suggesting anyone actually try this, there should be strict protocols in place.

    I certainly wouldn't recommend asking a friend for a random viral vector and just injecting yourself with it. Each new viral vector needs to be substantially tested in mammalian models first. Sorry to say, but I hope you have zero chance of convincing anyone injecting anything like this into you.

    In terms of risks, the immune response from your body could be very large and could KILL YOU, you are introducing foreign genes into your own body, you have no idea how that will play out, chances are high you will give yourself a disease. If the virus is replication-deficient, at least the infection will be localised (unless those infected cells enter your blood stream). There is also a chance you could cause an epidemic, so unless you know what you're doing - DON'T.

    Having that said, Adeno-associated viruses are small, stable and used commonly in gene therapies, majority of the human population have been exposed to wildtype variants of them with no known link to major diseases. If they are engineered to not replicate there is little risk of mutation and little risk of epidemics.

    They have also been used successfully in humans for gene therapies. For example.

    Yes, it is a fantastic way to create a non-invasive neural interface - With the right promoters and surface markers this will be more precise, cleaner and elegant than introducing various electrodes into the body and at a higher resolution.
  • edited August 2014
    Having that warning out of the way - to answer your question, optogenetics on humans, look at Sheila Nirenberg's work. It works well with neurons (the whole point of it) and have been successfully used in rat for Merkel cells as well.

    Yes I intend to use the smart watch as a stimulation source.

    We  have been working as of last week on creating our vectors and, after synthesis, will testing them with another lab on a related study.
  • I have an academic interest in sensory neurons, and unless I'm very much mistaken, you won't be able to target specific types of sensory neuron with perfect accuracy; there will inevitably be some crossover between modalities. The worry here would be that you end up hitting some proprioceptors (probably not an issue if you can manage a very localised infection at the skin's surface) or nociceptors (which would be much worse, and more like likely). Both of these would induce unwanted side effects (i.e. muscle twitching or pain, depending on the subtype)

    How did you come up with CCK and Math1 as promoters?
  • edited August 2014
    Thank-you for your response dokclaw, Nociceptors are certainly a concern because they branch out into the epidermis.

    However this is why we are studying CCK & Math1;

    "Recently, Haeberle isolated MCs from genetically modified mice expressing green fluorescent protein driven by the Math1 promotor. In the epidermis, the transcription factor Math1 is restricted to MCs, which allows for the selection of these cells by fluorescence-activated cell sorting"

    "We used optogenetics to selectively depolarize Merkel cells without directly stimulating their associated sensory afferents (Fig. 2a). A previous microarray screen identified cholecystokinin (Cck) as a Merkel-cell-specific transcript in the epidermis."

    To further localise the treatment, we can use a transdermal delivery system patch (matrix type), if possible, have the vector suspended in some solution that can limit to stratum basale - looking at removing the stratum corneum for efficacy.

    This is why I believe this route to be fairly safe and at least localised. It won't be clear until experimentation.

    We can also start looking at surface markers to further isolate the therapy but this raises complications, we will start running into size limits and might have to look at other vectors.

    Please let me know if I have missed anything or if there is any other concerns.
  • Merkel cells seem like a good bet; I was (stunningly) unaware of their existence! It's nice that you don't have to target neurons, because you almost certainly would get crossover.

    Both those papers look good; I was initially concerned that they were using a cre that was expressed in the progenitors, but not maintained in the mature cells. The Nature paper is using a CCK-cre, but the CCK would be expressed at mature stages anyway, so that's not an issue.

    Do you think that those promotors would be strong enough to drive functional levels of Channelrhodopsin? What about using a combination of viruses, like a CCK- or Math1-cre- expressing AAV, then a flox-stop-flox-ChR? 

    Additionally, do you have any leads on a better delivery method? It seems like you'll have to infect a huge number of non-target cells just to get a few Merkels. Do you have any way to package viral particles? If you could coat a virally-loaded particle with a KT1-18 antibody, then that should give you better specificity.
  • Regarding the density of Merkel cells in various areas, I think that the textbook is stating that the ratio of Merkel cells to sensory neurons is 50:1 in the forearm, and 5:1 in the fingertips, meaning that the resolution is higher in the fingertips (which makes sense). Whilst shape discrimination would be difficult with the smartwatch/forearm interface, you could still encode a ton of different information with varied patterns of light stimulus (intensity, frequency, direction)
  • There are 4 Mechanoreceptors that are worth looking into;
    Merkel receptor, Meissner corpuscle, Ruffini cylinder & Pacinian corpuscle.

    Haven't looked into them because some are deeper in the skin and there appears to be less of a knowledge-base around them, as well as the sensations they correspond to might feel weird.

    I couldn't find a regulatory network for Merkel Cells so I guess the expression rates are unknown (or some specialist might know) - once I've taken the drafts as far as I can - I'll get second opinions from more knowledgeable people. Those promoters have been used in the papers for identification to express large enough quantities of florescent protein, so it's a step in the right direction. Either way, experimentation will tell.

    Interesting, I'll pass on your ideas about the payload.

    I haven't looked too deeply into the delivery method, it's okay to infect a large number of cells to test proof of concept experimentally, as we should still have the specificity we need.

    But I agree for humans ultimately there needs to be as much specificity as possible to minimize any unwanted side effects, we'll need to identify surface markers. The Merkel Cell Polyomavirus, might have some answers here.

    I started digging up some papers;
    Merkel Cell Polyomavirus: A Newly Discovered Human Virus with Oncogenic Potential

    The Merkel cell polyomavirus minor capsid protein

    Structures of Merkel Cell Polyomavirus VP1 Complexes Define a Sialic Acid Binding Site Required for Infection

    But haven't looked too deeply yet, MCV binding seems too complex to attach to our vector, so maybe a delivery particle (DNA Origami?) might be a nice idea.

    Ah yes, you are right about the cell density, it doesn't have to be on the forearm, worst case - we can use some skin-safe liquid bonding cement to keep it in place.

    I can't seem to find any reliable information on nerve ending densities, from lightly touching myself with a toothpick i've noticed that the back of my neck and under my forearm seem to have a fairly decent density.

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