Optogenetics: cell types, mouse and vision aid
About this app
A virus with a promoter puts channelrhodopsin into just one cell type. The electrode excites every cell around its tip, light only the labelled ones. A light guide moves the whiskers of a mouse, and in retinitis pigmentosa ChrimsonR plus light goggles make ganglion cells sensitive to light.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
Only the right cells
In the brain different cell types lie close together. Optogenetics reaches just one of them: a virus carries the gene for channelrhodopsin into cells, and a promoter in front of it ensures that only one cell type makes the protein, for example CaMKIIα for excitatory pyramidal cells. An electrode, by contrast, excites every cell around its tip. In 2007 researchers around Karl Deisseroth moved the whiskers of living mice with a light guide in the motor cortex.
What the app shows
Three scenarios: brain tissue with pyramidal cells and interneurons, a virus with promoter and gene, electrode and light guide compared with bars for the firing cells per type. A mouse with a light guide whose whiskers follow the light, with a control without channelrhodopsin. And the retina in retinitis pigmentosa, where ChrimsonR makes ganglion cells sensitive to orange light. Cell positions, deflection and retina are simplified.
Try it yourself
Inject the virus and compare electrode and light: with light only labelled cells fire. Switch the promoter to interneurons. Play the mouse, also without channelrhodopsin. In the retina you switch the disease, the gene therapy and the light, and see why daylight is not enough and only the goggles trigger a signal.
Frequently asked questions
- How do you get channelrhodopsin into specific nerve cells only?
- With a virus as a gene shuttle and a cell-type-specific promoter. The virus enters many cells, but the gene is only read where the promoter is active. Researchers also often use mouse lines that make the enzyme Cre in one cell type only, together with a Cre-dependent virus.
- Can optogenetics help blind people?
- Partly. In 2021 Sahel, Roska and colleagues reported in Nature Medicine on a man with retinitis pigmentosa whose eye was injected with a virus carrying the gene for ChrimsonR. With goggles that project light pulses onto the retina, he could perceive, locate and count objects. It does not give sharp or colour vision; further trials are under way.
- What did the 2007 mouse experiment show?
- Aravanis, Deisseroth and colleagues put channelrhodopsin into cells of the motor cortex and passed a light guide through a small hole in the skull. Blue light moved the whiskers. Optogenetics had arrived in the brain of living mammals.
- What can I try in this app?
- You choose the promoter, inject the virus, stimulate with electrode or light, play the mouse with and without channelrhodopsin and switch disease, therapy and light in the retina. An explain mode guides you through all three scenarios.
Subject: Biology & neuroscience
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