Tech

Mitochondria Duplicate like tiny lenses in the eye


A watch that catches mosquitoes you through a network of microscopic lenses. You stare back, racquet in hand, watching the bloodsucker closely with your humble monolens eyes. But it turns out that the way you see each other – and the world – may have more in common than you think.

Research published last month in Scientific advance discovered that inside the mammalian eye, mitochondria, the organelle that powers cells, can act as a secondary lens, helping to focus light on photoreceptor pigments. light to convert light into nerve signals for the brain to interpret. The findings reveal a striking parallel between the eyes of mammals and the compound eyes of other insects and arthropods, suggesting that our eyes have a latent degree of optical complexity, and evolution Chemistry has found new uses for very old parts of our cellular anatomy.

The lens at the front of the eye focuses light from the environment onto a thin layer of tissue called the retina at the back. There, the photoreceptors — the cones that paint our world with color, and the rods that help us navigate in low light — absorb the light and transmit it. into nerve signals that are transmitted to the brain. But the light-sensitive pigments are located at the ends of the photoreceptors, just behind a thick bundle of mitochondria. The odd location of this bundle turns mitochondria into seemingly unnecessary light-scattering obstructions.

Mitochondria are the “last barrier” to light particles, Wei Li, a senior investigator at the National Eye Institute and senior author of the paper. For years, vision scientists could not understand the strange placement of these organelles — most cells, after all, have mitochondria that embrace their central organelle, the nucleus.

Some scientists suggest that bundles may have evolved to sit close to where light signals are converted into nerve signals, a process that requires a lot of energy, for easy energy pumping and distribution. fast. But then studies began to suggest that photoreceptors don’t need as many of these mitochondria for energy – instead, they can get more energy from a process called glycolysis. , occurs in the viscous cytoplasm of the cell.

Li and his team set out to understand the role of these mitochondrial bundles by analyzing the cone cells of a ground squirrel, a small mammal with excellent daytime vision but real The cell becomes night-blind because its photoreceptors are disproportionate cones.

After computer simulations suggested that mitochondrial bundles might have optical properties, Li and his team began experiments with real objects. They used a thin sample of the squirrel’s retina, the part of which they virtually removed all of its cells except parts of its cones, so that they “finished up with a lot of just a vesicle.” body” is neatly packed inside a membrane, Li said.

Shining light on this sample and examining it closely under a special confocal microscope built by John Ball, a scientist in Li’s lab and the study’s lead author, revealed a remarkable results. Light passing through the mitochondrial bundle emerges into a bright, focused beam. The researchers took photos and videos of beams of light passing through these microscopic lenses into the dark, where, in a living animal, light-sensitive pigments would wait.

Rather than being an obstacle, the mitochondrial bundles play an important role in helping to transmit as much light as possible to the photoreceptors with minimal loss, says Li.

With simulations, he and colleagues confirmed that the lensing effect is mainly caused by the mitochondrial bundle itself, not the membrane surrounding it (although the membrane plays some role). A few oddities about the ground squirrel’s natural history also helped demonstrate that the shape of the mitochondrial bundles is important to its ability to focus: During the hibernating months, the mitochondrial bundles of the ground squirrel’s mitochondria. it becomes disordered and compressed. When the researchers simulated what would happen when light passed through the mitochondrial bundle of a hibernating ground squirrel, they discovered that it didn’t focus the light as well as it did when it was elongated and orderly. high.



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